https://bugs.llvm.org/show_bug.cgi?id=38988
Bug ID: 38988
Summary: Failure to thread extractelement through phi w/undef
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: listm...@philipreames.com
CC: llvm-bugs@lists.llvm.org
$cat test.ll
define i32 @test(i1 %c, i32* nocapture readonly %p) {
br i1 %c, label %cond.load, label %else
cond.load: ; preds = %0
%1 = load i32, i32* %p, align 4
%2 = insertelement <1 x i32> undef, i32 %1, i32 0
br label %else
else: ; preds = %0, %cond.load
%res.phi.select = phi <1 x i32> [ %2, %cond.load ], [ undef, %0 ]
%3 = extractelement <1 x i32> %res.phi.select, i32 0
ret i32 %3
}
$opt -O3 test.ll -S
(same as input)
We should be producing:
define i32 @test(i1 %c, i32* nocapture readonly %p) {
br i1 %c, label %cond.load, label %else
cond.load:
%1 = load i32, i32* %p, align 4
br label %else
else:
%ret = phi i32 [%1, %cond.load], [undef, %0]
ret i32 %ret
}
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