https://gcc.gnu.org/g:879c99355c4ab2a86dd77db4ebf4acb70826b1c7
commit 879c99355c4ab2a86dd77db4ebf4acb70826b1c7
Author: Jakub Jelinek <ja...@redhat.com>
Date: Wed Oct 18 17:01:26 2023 +0200
cse: Workaround GCC < 5 bug in cse_insn [PR111852]
Before the r5-3834 commit for PR63362, GCC 4.8-4.9 refuses to compile
cse.cc which contains a variable with rtx_def type, because rtx_def
contains a union with poly_uint16 element. poly_int template has
defaulted default constructor and a variadic template constructor which
could have empty parameter pack. GCC < 5 treated it as non-trivially
constructible class and deleted rtunion and rtx_def default constructors.
For the cse_insn purposes, all we need is a variable with size and alignment
of rtx_def, not necessarily rtx_def itself, which we then memset to 0 and
fill in like rtx is normally allocated from heap, so this patch for
GCC_VERSION < 5000 uses an unsigned char array of the right size/alignment.
2023-10-18 Jakub Jelinek <ja...@redhat.com>
PR bootstrap/111852
* cse.cc (cse_insn): Add workaround for GCC 4.8-4.9, instead of
using rtx_def type for memory_extend_buf, use unsigned char
arrayy with size of rtx_def and its alignment.
(cherry picked from commit bc4bd69faf986326f6b0fd0400cdd6871577afd1)
Diff:
---
gcc/cse.cc | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/gcc/cse.cc b/gcc/cse.cc
index c46870059e6c..f9603fdfd437 100644
--- a/gcc/cse.cc
+++ b/gcc/cse.cc
@@ -4951,8 +4951,15 @@ cse_insn (rtx_insn *insn)
&& is_a <scalar_int_mode> (mode, &int_mode)
&& (extend_op = load_extend_op (int_mode)) != UNKNOWN)
{
+#if GCC_VERSION >= 5000
struct rtx_def memory_extend_buf;
rtx memory_extend_rtx = &memory_extend_buf;
+#else
+ /* Workaround GCC < 5 bug, fixed in r5-3834 as part of PR63362
+ fix. */
+ alignas (rtx_def) unsigned char memory_extended_buf[sizeof (rtx_def)];
+ rtx memory_extend_rtx = (rtx) &memory_extended_buf[0];
+#endif
/* Set what we are trying to extend and the operation it might
have been extended with. */
