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Avoid losing MEM_REF offset in MEM_EXPR adjustment for stack slot sharing

Message ID 20231213090748.535373858429@sourceware.org
State New
Headers show
Series Avoid losing MEM_REF offset in MEM_EXPR adjustment for stack slot sharing | expand

Commit Message

Richard Biener Dec. 13, 2023, 9:06 a.m. UTC 
When investigating PR111591 with respect to TBAA and stack slot sharing
I noticed we're eventually scrapping a [TARGET_]MEM_REF offset when
rewriting the VAR_DECL base of the MEM_EXPR to use a pointer to the
partition instead.  The following makes sure to preserve that.

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

	* emit-rtl.cc (set_mem_attributes_minus_bitpos): Preserve
	the offset when rewriting an exising MEM_REF base for
	stack slot sharing.
---
 gcc/emit-rtl.cc | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)
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Patch

diff --git a/gcc/emit-rtl.cc b/gcc/emit-rtl.cc
index 84b6833225e..4a7e420e7c0 100644
--- a/gcc/emit-rtl.cc
+++ b/gcc/emit-rtl.cc
@@ -2128,9 +2128,15 @@  set_mem_attributes_minus_bitpos (rtx ref, tree t, int objectp,
 	      tree *orig_base = &attrs.expr;
 	      while (handled_component_p (*orig_base))
 		orig_base = &TREE_OPERAND (*orig_base, 0);
-	      tree aptrt = reference_alias_ptr_type (*orig_base);
-	      *orig_base = build2 (MEM_REF, TREE_TYPE (*orig_base), *namep,
-				   build_int_cst (aptrt, 0));
+	      if (TREE_CODE (*orig_base) == MEM_REF
+		  || TREE_CODE (*orig_base) == TARGET_MEM_REF)
+		TREE_OPERAND (*orig_base, 0) = *namep;
+	      else
+		{
+		  tree aptrt = reference_alias_ptr_type (*orig_base);
+		  *orig_base = build2 (MEM_REF, TREE_TYPE (*orig_base),
+				       *namep, build_int_cst (aptrt, 0));
+		}
 	    }
 	}