https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111778
--- Comment #3 from CVS Commits ---
The master branch has been updated by Michael Meissner :
https://gcc.gnu.org/g:611eef7609f732db65c119a7eab6d50a5fdd5985
commit r14-4600-g611eef7609f732db65c119a7eab6d50a5fdd5985
Author: Michael Meissner
Date: Thu Oct 12 16:17:59 2023 -0400
PR111778, PowerPC: Do not depend on an undefined shift
I was building a cross compiler to PowerPC on my x86_86 workstation with
the
latest version of GCC on October 11th. I could not build the compiler on
the
x86_64 system as it died in building libgcc. I looked into it, and I
discovered the compiler was recursing until it ran out of stack space. If
I
build a native compiler with the same sources on a PowerPC system, it
builds
fine.
I traced this down to a change made around October 10th:
| commit 8f1a70a4fbcc6441c70da60d4ef6db1e5635e18a (HEAD)
| Author: Jiufu Guo
| Date: Tue Jan 10 20:52:33 2023 +0800
|
| rs6000: build constant via li/lis;rldicl/rldicr
|
| If a constant is possible left/right cleaned on a rotated value from
| a negative value of "li/lis". Then, using "li/lis ; rldicl/rldicr"
| to build the constant.
The code was doing a -1 << 64 which is undefined behavior because different
machines produce different results. On the x86_64 system, (-1 << 64)
produces
-1 while on a PowerPC 64-bit system, (-1 << 64) produces 0. The x86_64
then
recurses until the stack runs out of space.
If I apply this patch, the compiler builds fine on both x86_64 as a PowerPC
crosss compiler and on a native PowerPC system.
2023-10-12 Michael Meissner
gcc/
PR target/111778
* config/rs6000/rs6000.cc (can_be_built_by_li_lis_and_rldicl):
Protect
code from shifts that are undefined.
(can_be_built_by_li_lis_and_rldicr): Likewise.
(can_be_built_by_li_and_rldic): Protect code from shifts that
undefined. Also replace uses of 1ULL with HOST_WIDE_INT_1U.
