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* [gcc r12-6776] middle-end/100786 - constant folding from incompatible alias
@ 2022-01-20 15:50 Richard Biener
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From: Richard Biener @ 2022-01-20 15:50 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:5c12507f5d0bc080e4f346af99824e039236e61c
commit r12-6776-g5c12507f5d0bc080e4f346af99824e039236e61c
Author: Richard Biener <rguenther@suse.de>
Date: Thu Jan 20 14:25:51 2022 +0100
middle-end/100786 - constant folding from incompatible alias
The following avoids us ICEing doing constant folding from variables
with aliases of different types. The issue appears both in
folding and CCP and FRE can do more fancy stuff to still constant
fold cases where the load is smaller than the initializer so
defer it to there.
2022-01-20 Richard Biener <rguenther@suse.de>
PR middle-end/100786
* gimple-fold.cc (get_symbol_constant_value): Only return
values of compatible type to the symbol.
* gcc.dg/torture/pr100786.c: New testcase.
Diff:
---
gcc/gimple-fold.cc | 4 +++-
gcc/testsuite/gcc.dg/torture/pr100786.c | 9 +++++++++
2 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index 08d3cc214ff..3639aa20626 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -291,7 +291,9 @@ get_symbol_constant_value (tree sym)
if (val)
{
val = canonicalize_constructor_val (unshare_expr (val), sym);
- if (val && is_gimple_min_invariant (val))
+ if (val
+ && is_gimple_min_invariant (val)
+ && useless_type_conversion_p (TREE_TYPE (sym), TREE_TYPE (val)))
return val;
else
return NULL_TREE;
diff --git a/gcc/testsuite/gcc.dg/torture/pr100786.c b/gcc/testsuite/gcc.dg/torture/pr100786.c
new file mode 100644
index 00000000000..42f4e485593
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr100786.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+
+const double a = 0;
+extern int b __attribute__((alias("a")));
+void inc() { b++; }
+
+const int a2 = 0;
+extern double b2 __attribute__((alias("a2")));
+void inc2() { b2+=1; }
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