From 535115caaf97f5201fb528f67f15b4c52be5619d Mon Sep 17 00:00:00 2001
From: Richard Biener <rguenther@suse.de>
Date: Fri, 28 Feb 2025 10:36:11 +0100
Subject: [PATCH] tree-optimization/87984 - hard register assignments not
preserved
The following disables redundant store elimination to hard register
variables which isn't valid.
PR tree-optimization/87984
* tree-ssa-dom.cc (dom_opt_dom_walker::optimize_stmt): Do
not perform redundant store elimination to hard register
variables.
* tree-ssa-sccvn.cc (eliminate_dom_walker::eliminate_stmt):
Likewise.
* gcc.target/i386/pr87984.c: New testcase.
---
gcc/testsuite/gcc.target/i386/pr87984.c | 23 +++++++++++++++++++++++
gcc/tree-ssa-dom.cc | 4 +++-
gcc/tree-ssa-sccvn.cc | 2 ++
3 files changed, 28 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.target/i386/pr87984.c
diff --git a/gcc/testsuite/gcc.target/i386/pr87984.c b/gcc/testsuite/gcc.target/i386/pr87984.c
new file mode 100644
index 000000000000..39a6a7480f9e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr87984.c
@@ -0,0 +1,23 @@
+/* { dg-do run } */
+/* { dg-options "-O" } */
+
+__attribute__((noipa))
+int f(void)
+{
+ int o = 0;
+ for (int i = 0; i < 3; i++)
+ {
+ register int a asm("eax");
+ a = 1;
+ asm("add %1, %0" : "+r"(o) : "r"(a));
+ asm("xor %%eax, %%eax" ::: "eax");
+ }
+ return o;
+}
+
+int main()
+{
+ if (f() != 3)
+ __builtin_abort();
+ return 0;
+}
diff --git a/gcc/tree-ssa-dom.cc b/gcc/tree-ssa-dom.cc
index 291c3a4fa6b5..b1ac35e12fd9 100644
--- a/gcc/tree-ssa-dom.cc
+++ b/gcc/tree-ssa-dom.cc
@@ -2454,7 +2454,9 @@ dom_opt_dom_walker::optimize_stmt (basic_block bb, gimple_stmt_iterator *si,
/* Perform simple redundant store elimination. */
if (gimple_assign_single_p (stmt)
- && TREE_CODE (gimple_assign_lhs (stmt)) != SSA_NAME)
+ && TREE_CODE (gimple_assign_lhs (stmt)) != SSA_NAME
+ && (TREE_CODE (gimple_assign_lhs (stmt)) != VAR_DECL
+ || !DECL_HARD_REGISTER (gimple_assign_lhs (stmt))))
{
tree lhs = gimple_assign_lhs (stmt);
tree rhs = gimple_assign_rhs1 (stmt);
diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
index 146840664e2e..5a8c7c3aa10b 100644
--- a/gcc/tree-ssa-sccvn.cc
+++ b/gcc/tree-ssa-sccvn.cc
@@ -7081,6 +7081,8 @@ eliminate_dom_walker::eliminate_stmt (basic_block b, gimple_stmt_iterator *gsi)
if (gimple_assign_single_p (stmt)
&& !gimple_has_volatile_ops (stmt)
&& !is_gimple_reg (gimple_assign_lhs (stmt))
+ && (TREE_CODE (gimple_assign_lhs (stmt)) != VAR_DECL
+ || !DECL_HARD_REGISTER (gimple_assign_lhs (stmt)))
&& (TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME
|| is_gimple_min_invariant (gimple_assign_rhs1 (stmt))))
{
--
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