[llvm-bugs] [Bug 42436] New: [SCEV][LSR] Broken IR after LSR pass when compiling for armv8
via llvm-bugs
llvm-bugs at lists.llvm.org
Fri Jun 28 05:52:41 PDT 2019
https://bugs.llvm.org/show_bug.cgi?id=42436
Bug ID: 42436
Summary: [SCEV][LSR] Broken IR after LSR pass when compiling
for armv8
Product: libraries
Version: trunk
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Global Analyses
Assignee: unassignedbugs at nondot.org
Reporter: eleviant at accesssoftek.com
CC: llvm-bugs at lists.llvm.org
Created attachment 22161
--> https://bugs.llvm.org/attachment.cgi?id=22161&action=edit
reproducer
Compilation of large project for ARMv8 ended up with broken assembly code in
vector<_Tp, _Allocator>::insert(const_iterator __position, _ForwardIterator
__first, _ForwardIterator __last)
I investigated the problem and it seems to be in loop-reduce pass which creates
'sub' binary operation with these operands:
%8 = ptrtoint i8* %7 to i32
...
%10 = ptrtoint i8* undef to i32
...
.preheader:
%120 = sub i32 %10, %8
which should result to zero, but is in fact undefined.
One can reproduce it using the attached IR file and running:
opt -S -loop-reduce insert.ll
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