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st/glsl_to_tgsi: disable on-the-fly peephole for 64-bit operations

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This optimization is incorrect with 64-bit operations, because the
channel-splitting logic in emit_asm ends up being applied twice to
the source operands.

A lucky coincidence of how the writemask test works resulted in this
optimization basically never being applied anyway. As far as I can tell,
the only case where it would (incorrectly) have been applied is something
like

    dvec2 d;
    float x = (float)d.y;

which nobody seems to have ever done. But the moral equivalent does occur
in one of the component layout piglit test.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>
Reviewed-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Nicolai Hähnle 2016-10-07 16:15:30 +02:00
parent f5f3cadca3
commit 63193b9cde
1 changed files with 4 additions and 0 deletions
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4
src/mesa/state_tracker/st_glsl_to_tgsi.cpp
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@ -255,6 +255,7 @@ public:
ir_instruction *ir;
GLboolean cond_update;
bool saturate;
bool is_64bit_expanded;
st_src_reg sampler; /**< sampler register */
int sampler_base;
int sampler_array_size; /**< 1-based size of sampler array, 1 if not array */
@ -670,6 +671,7 @@ glsl_to_tgsi_visitor::emit_asm(ir_instruction *ir, unsigned op,
inst->src[1] = src1;
inst->src[2] = src2;
inst->src[3] = src3;
inst->is_64bit_expanded = false;
inst->ir = ir;
inst->dead_mask = 0;
/* default to float, for paths where this is not initialized
@ -790,6 +792,7 @@ glsl_to_tgsi_visitor::emit_asm(ir_instruction *ir, unsigned op,
dinst->prev = NULL;
}
this->instructions.push_tail(dinst);
dinst->is_64bit_expanded = true;
/* modify the destination if we are splitting */
for (j = 0; j < 2; j++) {
@ -2908,6 +2911,7 @@ glsl_to_tgsi_visitor::visit(ir_assignment *ir)
} else if (ir->rhs->as_expression() &&
this->instructions.get_tail() &&
ir->rhs == ((glsl_to_tgsi_instruction *)this->instructions.get_tail())->ir &&
!((glsl_to_tgsi_instruction *)this->instructions.get_tail())->is_64bit_expanded &&
type_size(ir->lhs->type) == 1 &&
l.writemask == ((glsl_to_tgsi_instruction *)this->instructions.get_tail())->dst[0].writemask) {
/* To avoid emitting an extra MOV when assigning an expression to a