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i965/vec4: Factor code out of DCE into a separate function.

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Will be reused in the next commit.

Reviewed-by: Eric Anholt <eric@anholt.net>
This commit is contained in:
Matt Turner 2014-03-12 14:23:40 -07:00
parent 9630ba6c6e
commit 1b8f143a23
1 changed files with 39 additions and 34 deletions
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73
src/mesa/drivers/dri/i965/brw_vec4.cpp
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@ -321,6 +321,44 @@ src_reg::equals(src_reg *r)
imm.u == r->imm.u);
}
static bool
try_eliminate_instruction(vec4_instruction *inst, int new_writemask)
{
if (new_writemask == 0) {
/* Don't dead code eliminate instructions that write to the
* accumulator as a side-effect. Instead just set the destination
* to the null register to free it.
*/
switch (inst->opcode) {
case BRW_OPCODE_ADDC:
case BRW_OPCODE_SUBB:
case BRW_OPCODE_MACH:
inst->dst = dst_reg(retype(brw_null_reg(), inst->dst.type));
break;
default:
if (inst->writes_flag()) {
inst->dst = dst_reg(retype(brw_null_reg(), inst->dst.type));
} else {
inst->remove();
}
}
return true;
} else if (inst->dst.writemask != new_writemask) {
switch (inst->opcode) {
case SHADER_OPCODE_TXF_CMS:
case SHADER_OPCODE_GEN4_SCRATCH_READ:
case VS_OPCODE_PULL_CONSTANT_LOAD:
case VS_OPCODE_PULL_CONSTANT_LOAD_GEN7:
break;
default:
inst->dst.writemask = new_writemask;
return true;
}
}
return false;
}
/**
* Must be called after calculate_live_intervals() to remove unused
* writes to registers -- register allocation will fail otherwise
@ -354,40 +392,7 @@ vec4_visitor::dead_code_eliminate()
}
}
if (write_mask == 0) {
progress = true;
/* Don't dead code eliminate instructions that write to the
* accumulator as a side-effect. Instead just set the destination
* to the null register to free it.
*/
switch (inst->opcode) {
case BRW_OPCODE_ADDC:
case BRW_OPCODE_SUBB:
case BRW_OPCODE_MACH:
inst->dst = dst_reg(retype(brw_null_reg(), inst->dst.type));
break;
default:
if (inst->writes_flag()) {
inst->dst = dst_reg(retype(brw_null_reg(), inst->dst.type));
} else {
inst->remove();
}
break;
}
} else if (inst->dst.writemask != write_mask) {
switch (inst->opcode) {
case SHADER_OPCODE_TXF_CMS:
case SHADER_OPCODE_GEN4_SCRATCH_READ:
case VS_OPCODE_PULL_CONSTANT_LOAD:
case VS_OPCODE_PULL_CONSTANT_LOAD_GEN7:
break;
default:
progress = true;
inst->dst.writemask = write_mask;
break;
}
}
progress = try_eliminate_instruction(inst, write_mask) || progress;
}
if (progress)