https://llvm.org/bugs/show_bug.cgi?id=31729
Bug ID: 31729
Summary: GVNHoist illegally hoists div instruction
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: ma...@braunis.de
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Created attachment 17884
--> https://llvm.org/bugs/attachment.cgi?id=17884&action=edit
C reproducer
The attached testcase performs a division (by zero) before checking the
condition present in the original sourcecode. The problem appears when
compiling test-suite/SingleSource/UnitTests/SignlessTypes/rem.c with the -Oz
flag.
I reduced the test to a small reproducer and will attach them here. Looking at
the -print-after-all output it seems GVNHoist is to blame and the problem goes
away with -gvn-max-hoisted=0 for me.
I can reproduce this on a macOS system with:
$ clang -Oz reduced.c
$ ./a.out
Floating point exception: 8
I attached a -O0 -emit-llvm .ll file for convenience but did not test whether
that reproduces as well.
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