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glsl: Reinstate constant-folding for division by zero

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Fixes regression: https://bugs.freedesktop.org/show_bug.cgi?id=34160

Commit e7c1f058d1 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@intel.com>

(cherry picked from commit 62c8c77333)
This commit is contained in:
Chad Versace 2011-02-14 13:22:39 -08:00 • committed by Ian Romanick
parent 89576ea75b
commit 614eff1fc6
1 changed files with 20 additions and 4 deletions
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24
src/glsl/ir_constant_expression.cpp
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@ -514,10 +514,18 @@ 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];
@ -536,10 +544,18 @@ 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