610 lines
20 KiB
ArmAsm
610 lines
20 KiB
ArmAsm
/// tmap_scanline_per - Pentium-Pro-optimized assembly version
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/// written by Brian Raiter, Mar 1998.
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/// lighting roundoff error fixed by Matt Mueller, July 1999
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/// The gist of the algorithm is as follows (note that this is
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/// pseudocode, not actual C):
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///
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/// int u = fx_u;
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/// int v = fx_v;
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/// int z = fx_z;
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/// int l = fx_l;
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/// int x, ubyz, vbyz;
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/// byte texmap[64][64] = pixptr;
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/// byte framebuffer[][bytes_per_row] = write_buffer;
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/// byte lightingtable[][256] = gr_fade_table;
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/// byte c;
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///
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/// for (x = fx_xleft ; x <= fx_xright ; ++x) {
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/// ubyz = (u / z) & 63;
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/// vbyz = (v / z) & 63;
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/// c = texmap[ubyz][vbyz];
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/// if (c != TRANSPARENT_COLOR)
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/// framebuffer[fx_y][x] = lightingtable[l / 65536][c];
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/// u += fx_du_dx;
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/// v += fx_dv_dx;
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/// z += fx_dz_dx;
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/// l += fx_dl_dx;
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/// }
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///
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/// The global variable Transparency_on is zero when it is known that
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/// there are no transparencies involved, so in that case we use a
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/// different loop that skips the transparency test.
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///
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/// The actual algorithm used here only does the division calculations
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/// every fourth pixel, and linearly interpolates the other three.
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/// Something along the lines of:
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///
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/// /* Initial values as before */
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/// int ubyz0, ubyz0, ubyz4, ubyz4, du1, dv1, i;
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///
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/// ubyz0 = u / z;
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/// vbyz0 = v / z;
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/// for (x = fx_xleft ; x <= fx_xright - 3 ; x += 4) {
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/// u += fx_du_dx * 4;
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/// v += fx_dv_dx * 4;
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/// z += fx_dz_dx * 4;
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/// ubyz4 = u / z;
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/// vbyz4 = v / z;
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/// du1 = (ubyz4 - ubyz0) / 4;
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/// dv1 = (vbyz4 - vbyz0) / 4;
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/// ubyz = ubyz0;
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/// vbyz = vbyz0;
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/// for (i = 0 ; i < 4 ; ++i) {
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/// c = texmap[ubyz & 63][vbyz & 63];
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/// if (c != TRANSPARENT_COLOR)
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/// framebuffer[fx_y][x + i] = lightingtable[l / 65536][c];
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/// ubyz += du1;
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/// vbyz += dv1;
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/// l += fx_dl_dx;
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/// }
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/// ubyz0 = ubyz4;
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/// vbyz0 = vbyz4;
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/// }
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/// for ( ; x <= fx_xright ; ++x) {
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/// /* Finish off remaining 0-3 pixels */
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/// }
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///
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/// So much for the basic overview.
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///
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/// In this version, the PPro's floating-point unit is pressed into
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/// service to do the actual divisions, so that 1/z can be calculated
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/// first, and the resulting reciprocal multiplied with u and v. These
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/// two products are then stored back out as integers. This keeps us
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/// down to doing only one division every four pixels, during which
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/// other integer instructions can be overlapped.
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///
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/// The algorithm actually divides 64 by z, so that the rounded-off
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/// products will effectively be stored with six fraction bits. This
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/// allows the algorithm to correct for minor floating-point roundoff
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/// errors. Two fraction bits are kept during the interpolation of the
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/// three middle pixels, which hopefully increases the accuracy of the
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/// approximations.
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///
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/// We only need the lowest six (integral) bits of u/z and v/z for
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/// each pixptr offset, so we only need eight bits of each fourth
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/// pair of values to figure the interpolation. Add with the two
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/// fractional bits we keep for extra precision flavor, this makes ten
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/// bits for each value, or twenty to store the full pair. To simplify
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/// the interpolation, the pair is packed into a single 32-bit
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/// register like so:
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///
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/// 3 2 1
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/// 1 4 6 8 0
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/// vvVVVVVVvv____________uuUUUUUUuu
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/// \v&63/ \u&63/
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///
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/// The unused bits between the u and v values permit the packed
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/// values to be added/subtracted without the u values spilling over
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/// into the v values. Then, the instructions "bswap %eax ; roll $6,
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/// %eax ; andl $0x0FFF, %eax" will right-justify the desired values
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/// into a pixptr offset.
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///
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/// The FP stack is loaded up with the values of u, v, and z,
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/// converted to floats. %ebp is used to hold the value of l, %esi is
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/// is set to pixptr, and %edi points to our current position in
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/// write_buffer.
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// This is used to abbreviate an annoying external variable name.
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.equ fadetbl, _gr_fade_table
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// The following macro encapsulates the floating-point instructions
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// that put the results of a prior division to use and prepare for the
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// next division. At the beginning of the macro, the FP stack contains
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// (from top to bottom): 64/z, z, u, v. The macro computes (64*u)/z,
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// which is stored in ubyz4, and (64*v)/z, which is stored in vybz4.
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// Simultaneous with this, the macro adds dudx to u, dvdx to v, and
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// dzdx to z, and finally puts 64 back onto the stack. At the end of
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// the macro, the stack contains: 64, z, u, v.
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.macro DoFPCalcs 0 // The FP stack after each instruction:
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// 64/z z u v
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fst %st(4) // 64/z z u v 64/z
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fxch %st(2) // u z 64/z v 64/z
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fmul %st, %st(4) // (64 * u) / z u z 64/z v u/z
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fadds (dudx) // u += dudx u' z 64/z v u/z
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fxch %st(3) // v z 64/z u' u/z
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fmul %st, %st(2) // (64 * v) / z v z v/z u' u/z
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fadds (dvdx) // v += dvdx v' z v/z u' u/z
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fxch %st(1) // z v' v/z u' u/z
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fadds (dzdx) // z += dzdx z' v' v/z u' u/z
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fxch %st(2) // v/z v' z' u' u/z
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flds (flt64) // 64 v/z v' z' u' u/z
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fxch %st(5) // u/z v/z v' z' u' 64
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fistpl (ubyz4) // v/z v' z' u' 64
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fistpl (vbyz4) // v' z' u' 64
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fxch %st(3) // 64 z' u' v'
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// (ready to start the next division)
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.endm
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#ifdef __linux__
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.equ _pixptr, pixptr
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.equ _gr_fade_table, gr_fade_table
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.equ _write_buffer, write_buffer
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.equ _bytes_per_row, bytes_per_row
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.equ _fx_xleft, fx_xleft
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.equ _fx_xright, fx_xright
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.equ _fx_y, fx_y
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.equ _fx_u, fx_u
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.equ _fx_v, fx_v
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.equ _fx_z, fx_z
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.equ _fx_l, fx_l
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.equ _fx_du_dx, fx_du_dx
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.equ _fx_dv_dx, fx_dv_dx
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.equ _fx_dz_dx, fx_dz_dx
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.equ _fx_dl_dx, fx_dl_dx
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.equ _Transparency_on, Transparency_on
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.globl asm_tmap_scanline_per
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#else
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.globl _asm_tmap_scanline_per
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#endif
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.extern _pixptr, _gr_fade_table, _write_buffer
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.extern _bytes_per_row, _fx_xleft, _fx_xright, _fx_y
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.extern _fx_u, _fx_v, _fx_z, _fx_l
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.extern _fx_du_dx, _fx_dv_dx, _fx_dz_dx, _fx_dl_dx
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.extern _Transparency_on
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//.local dudx, dvdx, dzdx, dldx, l
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//.local ubyz, vbyz, uvzero
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//.local lastquartet, lastpixel, ctwl
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//.local flt64
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.data
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.balign 4
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dudx: .long 0 // u's rate of change as a float
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dvdx: .long 0 // v's rate of change as a float
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dzdx: .long 0 // z's rate of change as a float
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dldx: .long 0 // l's rate of change as an integer
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l: .long 0 // the current l value
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ubyz4: .long 0 // u/z for the next iteration
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vbyz4: .long 0 // v/z for the next iteration
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uvzero: .long 0 // packed u/z and v/z values
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lastquartet: .long 0 // where to stop the 4-pixels loop
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lastpixel: .long 0 // where to stop drawing entirely
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flt64: .long 0x42800000 // 64.0 (what we divide z into)
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ctlwd: .long 0 // the pre-tweaked FPU control word
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.text
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.balign 4
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//
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// void c_tmap_scanline_per(void)
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//
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#ifdef __linux__
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asm_tmap_scanline_per:
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#else
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_asm_tmap_scanline_per:
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#endif
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// Save registers the compiler might be using.
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pushl %ebp
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pushl %edi
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pushl %esi
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// Kick the FPU into the lowest precision (still enough for our needs)
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// so as to speed up fdiv.
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fnstcw (ctlwd)
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movw (ctlwd), %ax
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movl %eax, %ebx
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andb $0xFC, %bh
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movw %bx, (ctlwd)
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fldcw (ctlwd)
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movw %ax, (ctlwd)
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// Multiply dudx, dvdx, and dzdx by four, and store locally, converted
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// into floating point.
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movl (_fx_du_dx), %eax
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sall $2, %eax
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movl %eax, (dudx)
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movl (_fx_dv_dx), %eax
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sall $2, %eax
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movl %eax, (dvdx)
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movl (_fx_dz_dx), %eax
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sall $2, %eax
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movl %eax, (dzdx)
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fildl (dudx)
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fildl (dvdx)
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fildl (dzdx)
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fxch %st(2)
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fstps (dudx)
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fstps (dvdx)
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fstps (dzdx)
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// bytes_per_row * fx_y is the offset for the current scanline. (We do
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// this now before we start the first FP division.)
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movl (_bytes_per_row), %eax
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xorl %edx, %edx
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mull (_fx_y)
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// Push v, u, z, and 64.0 onto the FPU stack, and then start
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// calculating the first 64 / z.
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fildl (_fx_v)
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fildl (_fx_u)
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fildl (_fx_z)
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flds (flt64)
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fdiv %st(1)
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// Meanwhile, get l and dldx (again, the latter multiplied by four).
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// l will be stored in %ebp for the duration. The original values are
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// divided by 256 so that the byte needed for the fade table offset
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// will be aligned.
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//Dividing by 256 is bad.. rounding errors and crap. We'll now do that
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//right before we need to access the table instead. -MM
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movl (_fx_l), %edx
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// sarl $8, %edx
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movl %edx, (l)
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movl (_fx_dl_dx), %edx
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// sarl $6, %edx
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sall $2, %edx
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movl %edx, (dldx)
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// Store pixptr, the pointer to our 64x64 texture map, in %esi. Store
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// write_buffer, the pointer to our frame buffer, in %edi. Then offset
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// %edi so that it points to pixel [fx_y][fx_xleft]. Calculate a
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// pointer to [fx_y][fx_xright + 1] so we know when to stop drawing.
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// Also calculate a pointer to [fx_y][(fx_xright + 1) & ~3] so we know
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// when to stop drawing four pixels at a time.
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movl (_pixptr), %esi
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movl (_write_buffer), %edi
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movl (_fx_xright), %ecx
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addl %eax, %edi
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incl %ecx
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addl %edi, %ecx
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movl %ecx, (lastpixel)
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addl (_fx_xleft), %edi
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movl %ecx, %eax
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subl %edi, %eax
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jle LeaveNow
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andl $3, %eax
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subl %eax, %ecx
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movl %ecx, (lastquartet)
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// Calculate round(64 * u / z) and round(64 * v / z), store, and
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// increment u, v, and z. Then start calculating the second 64 / z.
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DoFPCalcs
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fdiv %st(1)
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// Get our u/z and v/z values, lop off the bits we don't care
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// about, pack, and store in uvzero.
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movl (ubyz4), %eax
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incl %eax
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andl $0x3FF0, %eax
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shrl $4, %eax
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movl (vbyz4), %ebx
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incl %ebx
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andl $0x3FF0, %ebx
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shll $18, %ebx
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orl %eax, %ebx
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movl %ebx, (uvzero)
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// Are there at least four pixels to draw? If not, skip to the epilog
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// code.
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cmpl %ecx, %edi
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je LastBits
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// Do we need to test for transparencies?
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testl $(~0), (_Transparency_on)
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jnz LoopTransOn
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// If not, then use the simpler loop here.
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.balign 4
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LoopTransOff:
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// While the FPU is busy dividing, the latest u/z and v/z values are
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// retrieved, packed, and stored in uvzero (to be used again in the
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// next iteration). The old uvzero value, which contains the uv values
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// for pixel 0, gets subtracted from the new uvzero value to
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// determined the total change in u/z and v/z across the four pixels,
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// and this is divided by 4 to get the average. This average is then
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// used to estimate the values for pixels 1, $2, and 3. The old uvzero
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// value is used immediately to calculate pixel 0, while %eax, %ebx, and
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// %ecx are entrusted with the uv values for pixels 1, $2, and 3
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// respectively, while %edx is our "cleansed" register for using byte
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// values as memory pointer offsets. %ebp is loaded with the high byte
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// of l, forming half of the offset for the fade table lookup. (The
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// pixel from the texture-map bitmap supplies the other half.) Each
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// value is used to set its pixel as follows (assuming %eax holds our
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// packed uv value):
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//
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// a: bswapl %eax / move u and v to the
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// b: roll $6, %eax / far right
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// c: andl $0x0FFF, %eax / mask off extra bits
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// d: movb (%esi,%eax), %dl / get texture-map pixel
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// e: movb fadetbl(%edx,%ebp), %dl / correct for lighting
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// f: movb %dl, (%edi) / write to frame buffer
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//
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// The above is done four times, once for each pixel. Some of the
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// calculations may appear to be interleaved haphazardly, but the PPro
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// seems to like it this way.
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DoFPCalcs
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fdiv %st(1)
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xorl %edx, %edx
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movl (uvzero), %eax // %eax = uv for pixel 0
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bswapl %eax // 0 a
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roll $6, %eax // 0 b
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andl $0x0FFF, %eax // 0 c
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movb (%esi,%eax), %dl // 0 d
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movl (l), %ebp
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movl (dldx), %ecx
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addl %ebp, %ecx
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movl %ecx, (l)
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sarl $8, %ebp
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andl $0x7F00, %ebp
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movb fadetbl(%edx,%ebp), %dl // 0 e
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movl (vbyz4), %ebx
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incl %ebx
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andl $0x3FF0, %ebx
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movl (ubyz4), %ecx
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shll $18, %ebx
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incl %ecx
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andl $0x3FF0, %ecx
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shrl $4, %ecx
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movl (uvzero), %eax
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orl %ebx, %ecx
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movl %ecx, (uvzero)
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orl $0x1000, %ecx
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subl %eax, %ecx
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shrl $2, %ecx
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movb %dl, (%edi) // 0 f
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lea (%eax,%ecx,2), %ebx // %ebx = uv for pixel 2
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addl %ecx, %eax // %eax = uv for pixel 1
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bswapl %eax // 1 a
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roll $6, %eax // 1 b
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addl %ebx, %ecx // %ecx = uv for pixel 3
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bswapl %ebx // 2 a
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roll $6, %ebx // 2 b
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bswapl %ecx // 3 a
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andl $0x0FFF, %eax // 1 c
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andl $0x0FFF, %ebx // 2 c
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roll $6, %ecx // 3 b
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movb (%esi,%eax), %dl // 1 d
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movb fadetbl(%edx,%ebp), %al // 1 e
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movb (%esi,%ebx), %dl // 2 d
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movb fadetbl(%edx,%ebp), %bl // 2 e
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movb %al, 1(%edi) // 1 f
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andl $0x0FFF, %ecx // 3 c
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movb %bl, 2(%edi) // 2 f
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movb (%esi,%ecx), %dl // 3 d
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movb fadetbl(%edx,%ebp), %cl // 3 e
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movb %cl, 3(%edi) // 3 f
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addl $4, %edi
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cmpl (lastquartet), %edi
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jl LoopTransOff
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// Are there any pixels left at all?
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cmpl (lastpixel), %edi
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jne LastBits
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jmp LeaveNow
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.balign 4
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LoopTransOn:
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// This is similar to the LoopTransOff loop, the big change being that
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// each value retrieved from the texture map is tested against 255,
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// the transparent "color". A value of 255 in the texture map means to
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// let the existing value for that pixel in write_buffer go by
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// unchanged. Thus the code for each pixel looks something like this
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// instead:
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//
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// a: bswapl %eax / move u and v to the
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// b: roll $6, %eax / far right
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// c: andl $0x0FFF, %eax / mask off extra bits
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// d: movb (%esi,%eax), %dl / get texture-map pixel
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// e: cmpb $255, %dl / is pixel transparent?
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// f: sbbb %ah, %ah / yes:%ah=00, no:%ah=FF
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// g: movb fadetbl(%edx,%ebp), %dl / correct for lighting
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// h: movb (%edi), %al / get current pixel
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// i: xorb %al, %dl / combine the two
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// j: andb %dl, %ah / use %ah as a mask to
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// k: xorb %ah, %al / select which pixel
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// l: movb %al, (%edi) / write to frame buffer
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//
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// When the texture-map value is 255, the code simply writes the
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// original frame-buffer value back out again; otherwise the new pixel
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// is written instead. The ands and xors used to accomplish this bulk
|
|
// up the code, but on the whole it is better than having four
|
|
// unpredictable jumps in the loop.
|
|
|
|
DoFPCalcs
|
|
fdiv %st(1)
|
|
|
|
movl (uvzero), %eax // %eax = uv for pixel 0
|
|
bswapl %eax // 0 a
|
|
movl (dldx), %ecx
|
|
movl (l), %ebp
|
|
addl %ebp, %ecx
|
|
roll $6, %eax // 0 b
|
|
andl $0x0FFF, %eax // 0 c
|
|
xorl %edx, %edx
|
|
movb (%esi,%eax), %dl // 0 d
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|
cmpb $255, %dl // 0 e
|
|
sbbb %ah, %ah // 0 f
|
|
movl %ecx, (l)
|
|
sarl $8, %ebp
|
|
andl $0x7F00, %ebp
|
|
|
|
movb fadetbl(%edx,%ebp), %dl // 0 g
|
|
movb (%edi), %al // 0 h
|
|
xorb %al, %dl // 0 i
|
|
andb %dl, %ah // 0 j
|
|
xorb %ah, %al // 0 k
|
|
movb %al, (%edi) // 0 l
|
|
|
|
movl (vbyz4), %ebx
|
|
movl (ubyz4), %ecx
|
|
incl %ebx
|
|
andl $0x3FF0, %ebx
|
|
incl %ecx
|
|
andl $0x3FF0, %ecx
|
|
shll $18, %ebx
|
|
shrl $4, %ecx
|
|
orl %ebx, %ecx
|
|
movl (uvzero), %eax
|
|
movl %ecx, (uvzero)
|
|
orl $0x1000, %ecx
|
|
subl %eax, %ecx
|
|
shrl $2, %ecx
|
|
|
|
lea (%eax,%ecx,2), %ebx // %ebx = uv for pixel 2
|
|
addl %ecx, %eax // %eax = uv for pixel 1
|
|
bswapl %eax // 1 a
|
|
roll $6, %eax // 1 b
|
|
addl %ebx, %ecx // %ecx = uv for pixel 3
|
|
bswapl %ebx // 2 a
|
|
roll $6, %ebx // 2 b
|
|
andl $0x0FFF, %eax // 1 c
|
|
movb (%esi,%eax), %dl // 1 d
|
|
cmpb $255, %dl // 1 e
|
|
sbbb %ah, %ah // 1 f
|
|
bswapl %ecx // 3 a
|
|
movb 1(%edi), %al // 1 h
|
|
movb fadetbl(%edx,%ebp), %dl // 1 g
|
|
|
|
roll $6, %ecx // 3 b
|
|
andl $0x0FFF, %ebx // 2 c
|
|
xorb %al, %dl // 1 i
|
|
andb %dl, %ah // 1 j
|
|
movb (%esi,%ebx), %dl // 2 d
|
|
cmpb $255, %dl // 2 e
|
|
sbbb %bh, %bh // 2 f
|
|
movb fadetbl(%edx,%ebp), %dl // 2 g
|
|
andl $0x0FFF, %ecx // 3 c
|
|
movb 2(%edi), %bl // 2 h
|
|
xorb %bl, %dl // 2 i
|
|
andb %dl, %bh // 2 j
|
|
|
|
movb (%esi,%ecx), %dl // 3 d
|
|
cmpb $255, %dl // 3 e
|
|
sbbb %ch, %ch // 3 f
|
|
movb 3(%edi), %cl // 3 h
|
|
movb fadetbl(%edx,%ebp), %dl // 3 g
|
|
xorb %cl, %dl // 3 i
|
|
andb %dl, %ch // 3 j
|
|
|
|
xorb %ah, %al // 1 k
|
|
movb %al, 1(%edi) // 1 l
|
|
xorb %bh, %bl // 2 k
|
|
movb %bl, 2(%edi) // 2 l
|
|
xorb %ch, %cl // 3 k
|
|
movb %cl, 3(%edi) // 3 l
|
|
|
|
addl $4, %edi
|
|
cmpl (lastquartet), %edi
|
|
jl LoopTransOn
|
|
|
|
// Quit if there are none at all left.
|
|
|
|
cmpl (lastpixel), %edi
|
|
je LeaveNow
|
|
|
|
|
|
LastBits:
|
|
|
|
// Here we finish off the last one-to-three pixels assigned to us.
|
|
// Rather than calculating values for all four pixels, we just divide
|
|
// the difference by four and keep adding this average into the value
|
|
// as needed. (This code is not particularly optimized, by the way,
|
|
// since it represents such a miniscule amount of the running time.)
|
|
|
|
DoFPCalcs
|
|
movl (l), %ebp
|
|
sarl $8, %ebp
|
|
andl $0x7F00, %ebp
|
|
movl (ubyz4), %eax
|
|
incl %eax
|
|
andl $0x3FF0, %eax
|
|
shrl $4, %eax
|
|
movl (vbyz4), %ecx
|
|
incl %ecx
|
|
andl $0x3FF0, %ecx
|
|
shll $18, %ecx
|
|
orl %eax, %ecx
|
|
movl (uvzero), %ebx
|
|
orl $0x1000, %ecx
|
|
subl %ebx, %ecx
|
|
shrl $2, %ecx
|
|
xorl %edx, %edx
|
|
|
|
LoopLastBits: movl %ebx, %eax
|
|
bswapl %eax
|
|
roll $6, %eax
|
|
andl $0x0FFF, %eax
|
|
movb (%esi,%eax), %dl
|
|
cmpb $255, %dl
|
|
je LetPixelBy
|
|
movb fadetbl(%edx,%ebp), %dl
|
|
movb %dl, (%edi)
|
|
LetPixelBy: incl %edi
|
|
addl %ecx, %ebx
|
|
cmpl (lastpixel), %edi
|
|
jl LoopLastBits
|
|
|
|
|
|
LeaveNow:
|
|
|
|
// We're done! Clear the stacks, reset the FPU control word, and we
|
|
// are so out of here.
|
|
|
|
popl %esi
|
|
popl %edi
|
|
popl %ebp
|
|
fcompp
|
|
fcompp
|
|
fldcw (ctlwd)
|
|
ret
|