[PATCH] Fix missed CSE with a BLKmode entity

[PATCH] Fix missed CSE with a BLKmode entity

[Richard Biener]

The following fixes fallout of r10-7145-g1dc00a8ec9aeba which made
us cautionous about CSEing a load to an object that has padding bits.
The added check also triggers for BLKmode entities like STRING_CSTs
but by definition a BLKmode entity does not have padding bits.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

	PR tree-optimization/111751
	* tree-ssa-sccvn.cc (visit_reference_op_load): Exempt
	BLKmode result from the padding bits check.
---
 gcc/tree-ssa-sccvn.cc | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
index d2aab38c2d2..ce8ae8c6753 100644
--- a/gcc/tree-ssa-sccvn.cc
+++ b/gcc/tree-ssa-sccvn.cc
@@ -5747,8 +5747,9 @@ visit_reference_op_load (tree lhs, tree op, gimple *stmt)
     {
       /* Avoid the type punning in case the result mode has padding where
 	 the op we lookup has not.  */
-      if (maybe_lt (GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (result))),
-		    GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (op)))))
+      if (TYPE_MODE (TREE_TYPE (result)) != BLKmode
+	  && maybe_lt (GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (result))),
+		       GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (op)))))
 	result = NULL_TREE;
       else
 	{
-- 
2.35.3