https://bugs.llvm.org/show_bug.cgi?id=40954
Bug ID: 40954
Summary: LICM is moving an fdiv instruction out from under a
control dependence
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: Loop Optimizer
Assignee: unassignedb...@nondot.org
Reporter: eric.schwe...@pgroup.com
CC: llvm-bugs@lists.llvm.org
Created attachment 21560
--> https://bugs.llvm.org/attachment.cgi?id=21560&action=edit
reproducer of LICM moving an fdiv instruction
In the attached reproducer, the instruction %33 is control dependent upon the
branch in block L.LB2_498. When we run the following command,
% opt -licm bug.ll -o bug.llvm
and look at the output file, we see that the fdiv becomes %28 and has been
moved to block L.LB2_555, which is a predecessor of L.LB2_498. This code
motion introduces a floating-point exception into the flow path which was
previously guarded by the conditional branch.
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