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glsl: Fix constant-folding for reciprocal expressions

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Do not constant-fold a reciprocal if any component of the reciprocated
expression is 0. For example, do not constant-fold `1 / vec4(0, 1, 2, 3)`.

Incorrect, previous behavior
----------------------------
Reciprocals were constant-folded even when some component of the
reciprocated expression was 0. The incorrectly applied arithmetic was:
   1 / 0 := 0
For example,
   1 / vec4(0, 1, 2, 3) = vec4(0, 1, 1/2, 1/3)

NOTE: This is a candidate for the 7.9 and 7.10 branches.
This commit is contained in:
Chad Versace 2011-02-01 09:09:33 -08:00
parent 50278c0901
commit b3cf92aa91
1 changed files with 10 additions and 6 deletions
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16
src/glsl/ir_constant_expression.cpp
View file

@ -288,20 +288,24 @@ ir_expression::constant_expression_value()
break;
case ir_unop_rcp:
/* FINISHME: Emit warning when division-by-zero is detected. */
assert(op[0]->type->base_type == GLSL_TYPE_FLOAT);
for (unsigned c = 0; c < op[0]->type->components(); c++) {
switch (this->type->base_type) {
case GLSL_TYPE_UINT:
if (op[0]->value.u[c] != 0.0)
data.u[c] = 1 / op[0]->value.u[c];
if (op[0]->value.u[c] == 0.0)
return NULL;
data.u[c] = 1 / op[0]->value.u[c];
break;
case GLSL_TYPE_INT:
if (op[0]->value.i[c] != 0.0)
data.i[c] = 1 / op[0]->value.i[c];
if (op[0]->value.i[c] == 0.0)
return NULL;
data.i[c] = 1 / op[0]->value.i[c];
break;
case GLSL_TYPE_FLOAT:
if (op[0]->value.f[c] != 0.0)
data.f[c] = 1.0F / op[0]->value.f[c];
if (op[0]->value.f[c] == 0.0)
return NULL;
data.f[c] = 1.0F / op[0]->value.f[c];
break;
default:
assert(0);