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authorPierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>2019-08-28 10:56:52 +0200
committerMarek Olšák <marek.olsak@amd.com>2019-08-29 17:48:49 -0400
commit47cc660d9c19572e5ef2dce7c8ae1766a2ac9885 (patch)
tree283bb3e3eb0ee592d2e8aa5806b2f0e053442a98
parent8d03a6b70072858a7acb7ce92bcf26f9a69dee2d (diff)
glsl: replace 'x + (-x)' with constant 0
This fixes a hang in shadertoy for radeonsi where a buffer was initialized with: value -= value with value being undefined. In this case LLVM replace the operation with an assignment to NaN. Cc: 19.1 19.2 <mesa-stable@lists.freedesktop.org> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111241 Reviewed-by: Marek Olšák <marek.olsak@amd.com>
-rw-r--r--src/compiler/glsl/opt_algebraic.cpp12
1 files changed, 12 insertions, 0 deletions
diff --git a/src/compiler/glsl/opt_algebraic.cpp b/src/compiler/glsl/opt_algebraic.cpp
index ff4be269578..3147d25aea8 100644
--- a/src/compiler/glsl/opt_algebraic.cpp
+++ b/src/compiler/glsl/opt_algebraic.cpp
@@ -507,6 +507,18 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
if (is_vec_zero(op_const[1]))
return ir->operands[0];
+ /* Replace (x + (-x)) with constant 0 */
+ for (int i = 0; i < 2; i++) {
+ if (op_expr[i]) {
+ if (op_expr[i]->operation == ir_unop_neg) {
+ ir_rvalue *other = ir->operands[(i + 1) % 2];
+ if (other && op_expr[i]->operands[0]->equals(other)) {
+ return ir_constant::zero(ir, ir->type);
+ }
+ }
+ }
+ }
+
/* Reassociate addition of constants so that we can do constant
* folding.
*/