https://bugs.llvm.org/show_bug.cgi?id=47679
Bug ID: 47679
Summary: Miscompile for AArch64, possibly related to
llvm.umul.with.overflow.i64
Product: new-bugs
Version: 11.0
Hardware: Other
OS: All
Status: NEW
Severity: release blocker
Priority: P
Component: new bugs
Assignee: unassignedb...@nondot.org
Reporter: ki...@gmx.net
CC: htmldevelo...@gmail.com, llvm-bugs@lists.llvm.org
Created attachment 24004
--> https://bugs.llvm.org/attachment.cgi?id=24004&action=edit
unoptimized input IR
Hi,
I'm seeing test regressions with LLVM 11 (rc3 and rc4) on AArch64 for an
*unoptimized* function performing a i64 multiply-with-overflow-check
(apparently wrongly reporting overflows in some cases). Unfortunately, I don't
have an AArch64 box to test, and no according qemu setup, so this is a bit of a
shot in the dark. I've attached the source IR.
The generated *optimized* machine assembly is identical for LLVM 10 and 11, and
seems to work fine. The *unoptimized* assembly versions differ though; I don't
have a clue about AArch64, but in the optimized case and in the unoptimized 10
version, there's a `cmp` right after the `umulh`, and that's missing in the
unoptimized 11 version...
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