Mesa (master): glsl: Avoid division-by-zero during constant-folding

[Chad Versace]

Module: Mesa
Branch: master
Commit: e7c1f058d18f62aa4871aec623f994d7b68cb8c1
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=e7c1f058d18f62aa4871aec623f994d7b68cb8c1

Author: Chad Versace <chad.versace at intel.com>
Date:   Tue Feb  1 10:14:28 2011 -0800

glsl: Avoid division-by-zero during constant-folding

Avoid division-by-zero when constant-folding the following expression
types:
    ir_unop_rsq
    ir_binop_div
    ir_binop_mod

Fixes bugs:
https://bugs.freedesktop.org//show_bug.cgi?id=33306
https://bugs.freedesktop.org//show_bug.cgi?id=33508

Fixes Piglit tests:
glslparsertest/glsl2/div-by-zero-01.frag
glslparsertest/glsl2/div-by-zero-02.frag
glslparsertest/glsl2/div-by-zero-03.frag
glslparsertest/glsl2/modulus-zero-01.frag
glslparsertest/glsl2/modulus-zero-02.frag

NOTE: This is a candidate for the 7.9 and 7.10 branches.

---

 src/glsl/ir_constant_expression.cpp |   20 +++++++++++++++++++-
 1 files changed, 19 insertions(+), 1 deletions(-)

diff --git a/src/glsl/ir_constant_expression.cpp b/src/glsl/ir_constant_expression.cpp
index 321374f..2841fb3 100644
--- a/src/glsl/ir_constant_expression.cpp
+++ b/src/glsl/ir_constant_expression.cpp
@@ -314,9 +314,13 @@ ir_expression::constant_expression_value()
       break;
 
    case ir_unop_rsq:
+      /* 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++) {
-	 data.f[c] = 1.0F / sqrtf(op[0]->value.f[c]);
+	 float s = sqrtf(op[0]->value.f[c]);
+	 if (s == 0)
+	    return NULL;
+	 data.f[c] = 1.0F / s;
       }
       break;
 
@@ -511,6 +515,7 @@ ir_expression::constant_expression_value()
 
       break;
    case ir_binop_div:
+      /* FINISHME: Emit warning when division-by-zero is detected. */
       assert(op[0]->type == op[1]->type || op0_scalar || op1_scalar);
       for (unsigned c = 0, c0 = 0, c1 = 0;
 	   c < components;
@@ -518,12 +523,18 @@ ir_expression::constant_expression_value()
 
 	 switch (op[0]->type->base_type) {
 	 case GLSL_TYPE_UINT:
+	    if (op[1]->value.u[c1] == 0)
+	       return NULL;
 	    data.u[c] = op[0]->value.u[c0] / op[1]->value.u[c1];
 	    break;
 	 case GLSL_TYPE_INT:
+	    if (op[1]->value.i[c1] == 0)
+	       return NULL;
 	    data.i[c] = op[0]->value.i[c0] / op[1]->value.i[c1];
 	    break;
 	 case GLSL_TYPE_FLOAT:
+	    if (op[1]->value.f[c1] == 0)
+	       return NULL;
 	    data.f[c] = op[0]->value.f[c0] / op[1]->value.f[c1];
 	    break;
 	 default:
@@ -533,6 +544,7 @@ ir_expression::constant_expression_value()
 
       break;
    case ir_binop_mod:
+      /* FINISHME: Emit warning when division-by-zero is detected. */
       assert(op[0]->type == op[1]->type || op0_scalar || op1_scalar);
       for (unsigned c = 0, c0 = 0, c1 = 0;
 	   c < components;
@@ -540,12 +552,18 @@ ir_expression::constant_expression_value()
 
 	 switch (op[0]->type->base_type) {
 	 case GLSL_TYPE_UINT:
+	    if (op[1]->value.u[c1] == 0)
+	       return NULL;
 	    data.u[c] = op[0]->value.u[c0] % op[1]->value.u[c1];
 	    break;
 	 case GLSL_TYPE_INT:
+	    if (op[1]->value.i[c1] == 0)
+	       return NULL;
 	    data.i[c] = op[0]->value.i[c0] % op[1]->value.i[c1];
 	    break;
 	 case GLSL_TYPE_FLOAT:
+	    if (op[1]->value.f[c1] == 0)
+	       return NULL;
 	    /* We don't use fmod because it rounds toward zero; GLSL specifies
 	     * the use of floor.
 	     */