https://llvm.org/bugs/show_bug.cgi?id=31770
Bug ID: 31770
Summary: [InstCombine] fold extractelt(trunc(bitcast X))) ->
extractelt
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: spatel+l...@rotateright.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
We're missing a vector fold as Zvi noted here:
http://lists.llvm.org/pipermail/llvm-dev/2017-January/109539.html
define i32 @B(<8 x i32> %V) {
%B = bitcast <8 x i32> %V to <4 x i64>
%T = trunc <4 x i64> %B to <4 x i32>
%E = extractelement <4 x i32> %T, i32 1
ret i32 %E
}
On little-endian, this should be:
define i32 @B(<8 x i32> %V) {
%E = extractelement <8 x i32> %V, i32 2
ret i32 %E
}
There's a similar-looking fold already in InstCombine called
"foldVecTruncToExtElt()".
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