https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111778
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Michael Meissner <meiss...@gcc.gnu.org>: https://gcc.gnu.org/g:611eef7609f732db65c119a7eab6d50a5fdd5985 commit r14-4600-g611eef7609f732db65c119a7eab6d50a5fdd5985 Author: Michael Meissner <meiss...@linux.ibm.com> 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 <guoji...@linux.ibm.com> | 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 <meiss...@linux.ibm.com> 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.
