Because the meaning of the swizzles and writemasks involved is different,
so replacing the source would lead to different semantics.
---
src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
b/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
index 7b53aed..08da96d 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_copy_propagation.cpp
@@ -324,6 +324,13 @@ try_copy_propagate(const struct gen_device_info *devinfo,
value.file != ATTR)
return false;
+ /* If the type of the copy value is different from the type of the
+ * instruction then the swizzles and writemasks involved don't have the same
+ * meaning and simply replacing the source would produce different
semantics.
+ */
+ if (type_sz(value.type) != type_sz(inst->src[arg].type))
+ return false;
+
if (devinfo->gen >= 8 && (value.negate || value.abs) &&
is_logic_op(inst->opcode)) {
return false;
--
2.7.4
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