https://bugs.llvm.org/show_bug.cgi?id=49859
Bug ID: 49859
Summary: Miscompile with opt -licm -dse (due to bad memoryssa?)
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: mikael.hol...@ericsson.com
CC: llvm-bugs@lists.llvm.org
Created attachment 24721
--> https://bugs.llvm.org/attachment.cgi?id=24721&action=edit
bbi-54825_man_red.ll reproducer
Running
opt -enable-new-pm=0 -licm -dse bbi-54825_man_red.ll -S -o -
all stores to %sum are removed by dse. this then makes
%3 = load i8, i8* %sum, align 1
get the wrong value.
If we instead run
opt -enable-new-pm=0 -licm bbi-54825_man_red.ll -S -o - | opt -enable-new-pm=0
-dse -S -o -
several stores to %sum remains.
The same thing happens if we remove
AU.addPreserved<MemorySSAWrapperPass>();
from LICM.cpp.
Thus I think that LICM doesn't update memoryssa information as it should.
This looks very similar to an old bug:
https://bugs.llvm.org/show_bug.cgi?id=45927
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