summaryrefslogtreecommitdiff
path: root/src
diff options
context:
space:
mode:
Diffstat (limited to 'src')
-rw-r--r--src/mesa/drivers/dri/r300/compiler/r3xx_vertprog.c52
1 files changed, 46 insertions, 6 deletions
diff --git a/src/mesa/drivers/dri/r300/compiler/r3xx_vertprog.c b/src/mesa/drivers/dri/r300/compiler/r3xx_vertprog.c
index fc9c8f805a..6c1a038689 100644
--- a/src/mesa/drivers/dri/r300/compiler/r3xx_vertprog.c
+++ b/src/mesa/drivers/dri/r300/compiler/r3xx_vertprog.c
@@ -284,12 +284,52 @@ static void ei_mad(struct r300_vertex_program_code *vp,
struct prog_instruction *vpi,
GLuint * inst)
{
- inst[0] = PVS_OP_DST_OPERAND(PVS_MACRO_OP_2CLK_MADD,
- GL_FALSE,
- GL_TRUE,
- t_dst_index(vp, &vpi->DstReg),
- t_dst_mask(vpi->DstReg.WriteMask),
- t_dst_class(vpi->DstReg.File));
+ /* Remarks about hardware limitations of MAD
+ * (please preserve this comment, as this information is _NOT_
+ * in the documentation provided by AMD).
+ *
+ * As described in the documentation, MAD with three unique temporary
+ * source registers requires the use of the macro version.
+ *
+ * However (and this is not mentioned in the documentation), apparently
+ * the macro version is _NOT_ a full superset of the normal version.
+ * In particular, the macro version does not always work when relative
+ * addressing is used in the source operands.
+ *
+ * This limitation caused incorrect rendering in Sauerbraten's OpenGL
+ * assembly shader path when using medium quality animations
+ * (i.e. animations with matrix blending instead of quaternion blending).
+ *
+ * Unfortunately, I (nha) have been unable to extract a Piglit regression
+ * test for this issue - for some reason, it is possible to have vertex
+ * programs whose prefix is *exactly* the same as the prefix of the
+ * offending program in Sauerbraten up to the offending instruction
+ * without causing any trouble.
+ *
+ * Bottom line: Only use the macro version only when really necessary;
+ * according to AMD docs, this should improve performance by one clock
+ * as a nice side bonus.
+ */
+ if (vpi->SrcReg[0].File == PROGRAM_TEMPORARY &&
+ vpi->SrcReg[1].File == PROGRAM_TEMPORARY &&
+ vpi->SrcReg[2].File == PROGRAM_TEMPORARY &&
+ vpi->SrcReg[0].Index != vpi->SrcReg[1].Index &&
+ vpi->SrcReg[0].Index != vpi->SrcReg[2].Index &&
+ vpi->SrcReg[1].Index != vpi->SrcReg[2].Index) {
+ inst[0] = PVS_OP_DST_OPERAND(PVS_MACRO_OP_2CLK_MADD,
+ GL_FALSE,
+ GL_TRUE,
+ t_dst_index(vp, &vpi->DstReg),
+ t_dst_mask(vpi->DstReg.WriteMask),
+ t_dst_class(vpi->DstReg.File));
+ } else {
+ inst[0] = PVS_OP_DST_OPERAND(VE_MULTIPLY_ADD,
+ GL_FALSE,
+ GL_FALSE,
+ t_dst_index(vp, &vpi->DstReg),
+ t_dst_mask(vpi->DstReg.WriteMask),
+ t_dst_class(vpi->DstReg.File));
+ }
inst[1] = t_src(vp, &vpi->SrcReg[0]);
inst[2] = t_src(vp, &vpi->SrcReg[1]);
inst[3] = t_src(vp, &vpi->SrcReg[2]);