expand: EXTEND_BITINT CALL_EXPR results [PR114332]

The x86-64 and aarch64 psABIs (and the unwritten ia64 psABI part) say that
the padding bits of _BitInt are undefined, while the expansion internally
typically assumes that non-mode precision integers are sign/zero extended
and extends after operations.  We handle that mismatch with EXTEND_BITINT
done when reading from untrusted sources like function arguments, reading
_BitInt from memory etc. but otherwise keep relying on stuff being extended
internally (say in pseudos).
The return value of a function is an ABI boundary though too and we need
to extend that too.

2024-03-15  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/114332
	* expr.cc (expand_expr_real_1): EXTEND_BITINT also CALL_EXPR results.

diff --git a/gcc/expr.cc b/gcc/expr.cc
index f7d74525c15be76567bb5b084d387f33c216b2cb..2918c46973545c816ad5422a0ea00f020abbd4c0 100644 (file)
--- a/gcc/expr.cc
+++ b/gcc/expr.cc
@@ -12350,7 +12350,8 @@ expand_expr_real_1 (tree exp, rtx target, machine_mode tmode,
            return expand_builtin (exp, target, subtarget, tmode, ignore);
          }
       }
-      return expand_call (exp, target, ignore);
+      temp = expand_call (exp, target, ignore);
+      return EXTEND_BITINT (temp);
 
     case VIEW_CONVERT_EXPR:
       op0 = NULL_RTX;

diff --git a/gcc/testsuite/gcc.dg/torture/bitint-64.c b/gcc/testsuite/gcc.dg/torture/bitint-64.c
new file mode 100644 (file)
index 0000000..8f0f21c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/bitint-64.c
@@ -0,0 +1,22 @@
+/* PR middle-end/114332 */
+/* { dg-do run { target bitint } } */
+/* { dg-options "-std=c23 -fwrapv" } */
+/* { dg-skip-if "" { ! run_expensive_tests }  { "*" } { "-O0" "-O2" } } */
+/* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */
+
+enum E { E22 = 22 } e = E22;
+
+_BitInt (5)
+foo (void)
+{
+  _Atomic _BitInt (5) b = 0;
+  b += e;
+  return b;
+}
+
+int
+main ()
+{
+  if (foo () != -10)
+    __builtin_abort ();
+}