http://llvm.org/bugs/show_bug.cgi?id=15737
Bug ID: 15737
Summary: Assert when combining an AND of two FCMPs.
Product: clang
Version: trunk
Hardware: Macintosh
OS: MacOS X
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
Created attachment 10346
--> http://llvm.org/bugs/attachment.cgi?id=10346&action=edit
Tarball of preprocessed source, run script, and backtrace.
When compiling this function at -O2, Clang issues an assert:
int kung( float a, double b ) {
return (a == a) & (b == b);
}
The assert is:
Assertion failed: (getOperand(0)->getType() == getOperand(1)->getType() &&
"Both operands to FCmp instruction are not of the same type!"), function
FCmpInst, file /Users/xkrebstarx/clang/llvm/include/llvm/IR/Instructions.h,
line 1117.
We begin with a float "a" and double "b":
> (fcmp oeq a, a) & (fcmp oeq b, b)
After canonicalization in InstCombine, we end up with the expression:
> (fcmp ord a, 0.0) & (fcmp ord b, 0.0)
The bug manifest is in InstCombiner::FoldAndOfFCmps(FCmpInst *LHS, FCmpInst
*RHS), when trying to perform this transformation:
> (fcmp ord x, c) & (fcmp ord y, c) -> (fcmp ord x, y)
This is all fine, except that the FCmpInst constructor in the IRBuilder
requires that both operands to the new fcmp are the same type, which they are
not.
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