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From: Michael Meissner <meissner@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc(refs/users/meissner/heads/work139)] Update ChangeLog.meissner Date: Mon, 16 Oct 2023 18:23:46 +0000 (GMT) [thread overview] Message-ID: <20231016182346.3FC0F385CC87@sourceware.org> (raw) https://gcc.gnu.org/g:39d18e7b7cb4e717065fbb2c4b705f11be848fe2 commit 39d18e7b7cb4e717065fbb2c4b705f11be848fe2 Author: Michael Meissner <meissner@linux.ibm.com> Date: Thu Oct 12 00:10:00 2023 -0400 Update ChangeLog.meissner Diff: --- gcc/ChangeLog.meissner | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) diff --git a/gcc/ChangeLog.meissner b/gcc/ChangeLog.meissner index 9f1909094939..5021e3ab1f2f 100644 --- a/gcc/ChangeLog.meissner +++ b/gcc/ChangeLog.meissner @@ -1,5 +1,77 @@ +==================== Branch work139, patch #1 ==================== + +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 <guojiufu@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 <meissner@linux.ibm.com> + +gcc/ + + PR target/111778 + * config/rs6000/rs6000.cc (can_be_built_by_li_lis_and_rldicl): Do not + use a shift left by the number of bits in a host wide int. + ==================== Branch work139, baseline ==================== +Add ChangeLog.meissner and REVISION. + +2023-10-11 Michael Meissner <meissner@linux.ibm.com> + +gcc/ + + * REVISION: New file for branch. + * ChangeLog.meissner: New file. + +gcc/c-family/ + + * ChangeLog.meissner: New file. + +gcc/c/ + + * ChangeLog.meissner: New file. + +gcc/cp/ + + * ChangeLog.meissner: New file. + +gcc/fortran/ + + * ChangeLog.meissner: New file. + +gcc/testsuite/ + + * ChangeLog.meissner: New file. + +libgcc/ + + * ChangeLog.meissner: New file. + 2023-10-11 Michael Meissner <meissner@linux.ibm.com> Clone branch
next reply other threads:[~2023-10-16 18:23 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-10-16 18:23 Michael Meissner [this message] -- strict thread matches above, loose matches on Subject: below -- 2023-10-16 18:24 Michael Meissner 2023-10-16 18:24 Michael Meissner 2023-10-16 18:24 Michael Meissner 2023-10-16 18:24 Michael Meissner 2023-10-16 18:24 Michael Meissner 2023-10-16 18:24 Michael Meissner 2023-10-12 21:54 Michael Meissner 2023-10-12 21:54 Michael Meissner 2023-10-12 21:54 Michael Meissner 2023-10-12 20:46 Michael Meissner 2023-10-12 4:51 Michael Meissner 2023-10-12 4:10 Michael Meissner
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