The sign bit of a sign-extending load cannot be known until runtime,
so don't attempt to simplify it in the combiner.
2024-01-11 Greg McGary <g...@rivosinc.com>
PR rtl-optimization/113010
* combine.cc (expand_compound_operation): Don't simplify
SIGN_EXTEND of a MEM on WORD_REGISTER_OPERATIONS targets
* gcc.c-torture/execute/pr113010.c: New test.
---
gcc/combine.cc | 5 +++++
gcc/testsuite/gcc.c-torture/execute/pr113010.c | 9 +++++++++
2 files changed, 14 insertions(+)
create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr113010.c
diff --git a/gcc/combine.cc b/gcc/combine.cc
index 812553c091e..ba587184dfc 100644
--- a/gcc/combine.cc
+++ b/gcc/combine.cc
@@ -7208,6 +7208,11 @@ expand_compound_operation (rtx x)
if (len == 0)
return x;
+ /* Sign-extending loads can never be simplified at compile time. */
+ if (WORD_REGISTER_OPERATIONS && MEM_P (XEXP (x, 0))
+ && load_extend_op (inner_mode) == SIGN_EXTEND)
+ return x;
+
break;
case ZERO_EXTRACT:
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr113010.c
b/gcc/testsuite/gcc.c-torture/execute/pr113010.c
new file mode 100644
index 00000000000..a95c613c1df
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr113010.c
@@ -0,0 +1,9 @@
+int minus_1 = -1;
+
+int
+main ()
+{
+ if ((0, 0xfffffffful) >= minus_1)
+ __builtin_abort ();
+ return 0;
+}
--
2.34.1
