* [PATCH] wrong code with points-to and volatile
@ 2024-05-16 11:36 Richard Biener
0 siblings, 0 replies; only message in thread
From: Richard Biener @ 2024-05-16 11:36 UTC (permalink / raw)
To: gcc-patches
The following fixes points-to analysis which ignores the fact that
volatile qualified refs can result in any pointer.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
Btw, I noticed this working on ptr-vs-ptr compare simplification
using points-to info and running into gcc.c-torture/execute/pr64242.c
* tree-ssa-structalias.cc (get_constraint_for_1): For
volatile referenced or decls use ANYTHING.
* gcc.dg/tree-ssa/alias-38.c: New testcase.
---
gcc/testsuite/gcc.dg/tree-ssa/alias-38.c | 14 ++++++++++++++
gcc/tree-ssa-structalias.cc | 7 +++++++
2 files changed, 21 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/alias-38.c
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/alias-38.c b/gcc/testsuite/gcc.dg/tree-ssa/alias-38.c
new file mode 100644
index 00000000000..a5c41493473
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/alias-38.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int x;
+int y;
+
+int main ()
+{
+ int *volatile p = &x;
+ return (p != &y);
+}
+
+/* { dg-final { scan-tree-dump " != &y" "optimized" } } */
+/* { dg-final { scan-tree-dump-not "return 1;" "optimized" } } */
diff --git a/gcc/tree-ssa-structalias.cc b/gcc/tree-ssa-structalias.cc
index 9c63305063c..f0454bea2ea 100644
--- a/gcc/tree-ssa-structalias.cc
+++ b/gcc/tree-ssa-structalias.cc
@@ -3575,6 +3575,10 @@ get_constraint_for_1 (tree t, vec<ce_s> *results, bool address_p,
}
case tcc_reference:
{
+ if (TREE_THIS_VOLATILE (t))
+ /* Fall back to anything. */
+ break;
+
switch (TREE_CODE (t))
{
case MEM_REF:
@@ -3676,6 +3680,9 @@ get_constraint_for_1 (tree t, vec<ce_s> *results, bool address_p,
}
case tcc_declaration:
{
+ if (VAR_P (t) && TREE_THIS_VOLATILE (t))
+ /* Fall back to anything. */
+ break;
get_constraint_for_ssa_var (t, results, address_p);
return;
}
--
2.35.3
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