Mesa (master): ir_constant: Don't assert on out-of-bounds array accesses
Ian Romanick
idr at kemper.freedesktop.org
Tue Aug 17 20:05:22 UTC 2010
Module: Mesa
Branch: master
Commit: 664364052f362af2789e6b0fa88b6a5ba66ba936
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=664364052f362af2789e6b0fa88b6a5ba66ba936
Author: Ian Romanick <ian.d.romanick at intel.com>
Date: Tue Aug 17 12:57:28 2010 -0700
ir_constant: Don't assert on out-of-bounds array accesses
Several optimization paths, including constant folding, can lead to
accessing an ir_constant array with an out of bounds index. The GLSL
spec lets us produce "undefined" results, but it does not let us
crash.
Fixes piglit test case glsl-array-bounds-01 and glsl-array-bounds-03.
---
src/glsl/ir.cpp | 16 +++++++++++++++-
1 files changed, 15 insertions(+), 1 deletions(-)
diff --git a/src/glsl/ir.cpp b/src/glsl/ir.cpp
index dd059e4..ebb5927 100644
--- a/src/glsl/ir.cpp
+++ b/src/glsl/ir.cpp
@@ -519,7 +519,21 @@ ir_constant *
ir_constant::get_array_element(unsigned i) const
{
assert(this->type->is_array());
- assert(i < this->type->length);
+
+ /* From page 35 (page 41 of the PDF) of the GLSL 1.20 spec:
+ *
+ * "Behavior is undefined if a shader subscripts an array with an index
+ * less than 0 or greater than or equal to the size the array was
+ * declared with."
+ *
+ * Most out-of-bounds accesses are removed before things could get this far.
+ * There are cases where non-constant array index values can get constant
+ * folded.
+ */
+ if (int(i) < 0)
+ i = 0;
+ else if (i >= this->type->length)
+ i = this->type->length - 1;
return array_elements[i];
}
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