From: Qing Zhao <qing.zhao@oracle.com>
Date: Thu, 18 Sep 2025 15:50:38 +0000 (+0000)
Subject: Fix SRA issue with -ftrivial-auto-var-init= [PR121894]
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=r16-3956-gf613fdc6920c83;p=thirdparty%2Fgcc.git

Fix SRA issue with -ftrivial-auto-var-init= [PR121894]

In tree-sra.cc, for the following stmt (initialization in source code):
s = {};

for the above lhs "s", the field "grp_assignment_write" of the created
struct access is 1;

however, for the following stmt (compiler added initialization):
s = .DEFERRED_INIT (size, init_type, &"s"[0]);

for the above lhs "s", the field "grp_assignment_write" of the created
struct access is 0;

Since the field "grp_assignment_write" of the struct access for the
corresponding LHS "s" is not set correctly when the RHS is .DEFERRED_INIT,
SRA phase didn't do a correct transformation for call to .DEFERRED_INIT.

To fix this issue, we should set the field "grp_assignment_write" correctly
for .DEFERRED_INIT.

	PR tree-optimization/121894

gcc/ChangeLog:

	* tree-sra.cc (scan_function): Set grp_assignment_write to 1 when
	specially handle call to .DEFERRED_INIT.

gcc/testsuite/ChangeLog:

	* g++.dg/opt/auto-init-sra-pr121894.C: New test.
---

diff --git a/gcc/testsuite/g++.dg/opt/auto-init-sra-pr121894.C b/gcc/testsuite/g++.dg/opt/auto-init-sra-pr121894.C
new file mode 100644
index 00000000000..b1e5a59ffe7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/auto-init-sra-pr121894.C
@@ -0,0 +1,22 @@
+/* Verify that SRA total scalarization will not be confused by padding
+   and also not confused by auto initialization.  */
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-esra -ftrivial-auto-var-init=pattern" } */
+
+struct S { int a, b, c, d; };
+void bar (int, int, int, int);
+
+void
+foo ()
+{
+  S s;
+  s.a = 1;
+  s.c = 2;
+  s.d = 3;
+  s.a++;
+  s.c++;
+  s.d++;
+  bar (s.a, s.b, s.c, s.d);
+}
+
+/* { dg-final { scan-tree-dump-times "DEFERRED_INIT" 4 "esra" } } */
diff --git a/gcc/tree-sra.cc b/gcc/tree-sra.cc
index 921664ef470..cb0f518ff03 100644
--- a/gcc/tree-sra.cc
+++ b/gcc/tree-sra.cc
@@ -1678,7 +1678,13 @@ scan_function (void)
 		  /* If the STMT is a call to DEFERRED_INIT, avoid setting
 		     cannot_scalarize_away_bitmap.  */
 		  if (gimple_call_internal_p (stmt, IFN_DEFERRED_INIT))
-		    ret |= !!build_access_from_expr_1 (t, stmt, true);
+		    {
+		      struct access *access
+			= build_access_from_expr_1 (t, stmt, true);
+		      if (access)
+			access->grp_assignment_write = 1;
+		      ret |= access != NULL;
+		    }
 		  else
 		    ret |= build_access_from_expr (t, stmt, true);
 		}