Mesa (7.9): glsl: Reinstate constant-folding for division by zero
Ian Romanick
idr at kemper.freedesktop.org
Tue Mar 1 00:04:40 UTC 2011
Module: Mesa
Branch: 7.9
Commit: e1e829689de7f986091ffa657ff3e4f9fdd750d9
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=e1e829689de7f986091ffa657ff3e4f9fdd750d9
Author: Chad Versace <chad.versace at intel.com>
Date: Mon Feb 14 13:22:39 2011 -0800
glsl: Reinstate constant-folding for division by zero
Fixes regression: https://bugs.freedesktop.org/show_bug.cgi?id=34160
Commit e7c1f058d18f62aa4871aec623f994d7b68cb8c1 disabled constant-folding
when division-by-zero occured. This was a mistake, because the spec does
allow division by zero. (From section 5.9 of the GLSL 1.20 spec: Dividing
by zero does not cause an exception but does result in an unspecified
value.)
For floating-point division, the original pre-e7c1f05 behavior is
reinstated.
For integer division, constant-fold 1/0 to 0.
Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
(cherry picked from commit 62c8c773334c1b0cdd484997a4ccec8945713f8c)
---
src/glsl/ir_constant_expression.cpp | 24 ++++++++++++++++++++----
1 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/src/glsl/ir_constant_expression.cpp b/src/glsl/ir_constant_expression.cpp
index 77dac58..1054489 100644
--- a/src/glsl/ir_constant_expression.cpp
+++ b/src/glsl/ir_constant_expression.cpp
@@ -508,10 +508,18 @@ ir_expression::constant_expression_value()
switch (op[0]->type->base_type) {
case GLSL_TYPE_UINT:
- data.u[c] = op[0]->value.u[c0] / op[1]->value.u[c1];
+ if (op[1]->value.u[c1] == 0) {
+ data.u[c] = 0;
+ } else {
+ data.u[c] = op[0]->value.u[c0] / op[1]->value.u[c1];
+ }
break;
case GLSL_TYPE_INT:
- data.i[c] = op[0]->value.i[c0] / op[1]->value.i[c1];
+ if (op[1]->value.i[c1] == 0) {
+ data.i[c] = 0;
+ } else {
+ data.i[c] = op[0]->value.i[c0] / op[1]->value.i[c1];
+ }
break;
case GLSL_TYPE_FLOAT:
data.f[c] = op[0]->value.f[c0] / op[1]->value.f[c1];
@@ -530,10 +538,18 @@ ir_expression::constant_expression_value()
switch (op[0]->type->base_type) {
case GLSL_TYPE_UINT:
- data.u[c] = op[0]->value.u[c0] % op[1]->value.u[c1];
+ if (op[1]->value.u[c1] == 0) {
+ data.u[c] = 0;
+ } else {
+ data.u[c] = op[0]->value.u[c0] % op[1]->value.u[c1];
+ }
break;
case GLSL_TYPE_INT:
- data.i[c] = op[0]->value.i[c0] % op[1]->value.i[c1];
+ if (op[1]->value.i[c1] == 0) {
+ data.i[c] = 0;
+ } else {
+ data.i[c] = op[0]->value.i[c0] % op[1]->value.i[c1];
+ }
break;
case GLSL_TYPE_FLOAT:
/* We don't use fmod because it rounds toward zero; GLSL specifies
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