The following fixes a missed check in the simple_iv attempt
to simplify (signed T)((unsigned T) base + step) where it
allows a truncating inner conversion leading to wrong code.
Bootstrap and regtest running on x86_64-unknown-linux-gnu.
PR tree-optimization/111445
* tree-scalar-evolution.cc (simple_iv_with_niters):
Add missing check for a sign-conversion.
* gcc.dg/torture/pr111445.c: New testcase.
---
gcc/testsuite/gcc.dg/torture/pr111445.c | 29 +++++++++++++++++++++++++
gcc/tree-scalar-evolution.cc | 3 ++-
2 files changed, 31 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/torture/pr111445.c
diff --git a/gcc/testsuite/gcc.dg/torture/pr111445.c
b/gcc/testsuite/gcc.dg/torture/pr111445.c
new file mode 100644
index 00000000000..320e0b90675
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr111445.c
@@ -0,0 +1,29 @@
+/* { dg-do run } */
+
+extern void abort (void);
+short a, b;
+unsigned char c = 255;
+unsigned cnt;
+void __attribute__((noipa))
+check (int x)
+{
+ if (x != 0)
+ abort ();
+ cnt++;
+}
+int main()
+{
+ int d;
+ unsigned char e;
+ d = 0;
+ for (; a >= 0; a--) {
+ int *f = &d;
+ *f = c;
+ }
+ e = 0;
+ for (; (unsigned char)(d - 255) + e <= 1; e++)
+ check (b);
+ if (cnt != 2)
+ abort ();
+ return 0;
+}
diff --git a/gcc/tree-scalar-evolution.cc b/gcc/tree-scalar-evolution.cc
index 7cafe5ce576..95a15fe0988 100644
--- a/gcc/tree-scalar-evolution.cc
+++ b/gcc/tree-scalar-evolution.cc
@@ -3286,7 +3286,8 @@ simple_iv_with_niters (class loop *wrto_loop, class loop
*use_loop,
type = TREE_TYPE (iv->base);
e = TREE_OPERAND (iv->base, 0);
- if (TREE_CODE (e) != PLUS_EXPR
+ if (!tree_nop_conversion_p (type, TREE_TYPE (e))
+ || TREE_CODE (e) != PLUS_EXPR
|| TREE_CODE (TREE_OPERAND (e, 1)) != INTEGER_CST
|| !tree_int_cst_equal (iv->step,
fold_convert (type, TREE_OPERAND (e, 1))))
--
2.35.3
