Mesa (master): glsl: Fix constant-folding for reciprocal expressions
Chad Versace
chadversary at kemper.freedesktop.org
Wed Feb 2 18:01:34 UTC 2011
Module: Mesa
Branch: master
Commit: b3cf92aa916ee0537ee37723c23a9897ac9cd3e0
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=b3cf92aa916ee0537ee37723c23a9897ac9cd3e0
Author: Chad Versace <chad.versace at intel.com>
Date: Tue Feb 1 09:09:33 2011 -0800
glsl: Fix constant-folding for reciprocal expressions
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.
---
src/glsl/ir_constant_expression.cpp | 16 ++++++++++------
1 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/src/glsl/ir_constant_expression.cpp b/src/glsl/ir_constant_expression.cpp
index cf958aa..321374f 100644
--- a/src/glsl/ir_constant_expression.cpp
+++ b/src/glsl/ir_constant_expression.cpp
@@ -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);
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