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-rw-r--r--src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp7
1 files changed, 7 insertions, 0 deletions
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
index eca5d0cb01c..6e48be74852 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
@@ -1135,6 +1135,13 @@ vec4_visitor::try_emit_mad(ir_expression *ir)
bool
vec4_visitor::try_emit_b2f_of_compare(ir_expression *ir)
{
+ /* This optimization relies on CMP setting the destination to 0 when
+ * false. Early hardware only sets the least significant bit, and
+ * leaves the other bits undefined. So we can't use it.
+ */
+ if (brw->gen < 6)
+ return false;
+
ir_expression *const cmp = ir->operands[0]->as_expression();
if (cmp == NULL)