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[LoopReroll] Don't crash on dead code

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If a PHI has no users, don't crash; bail gracefully. This shouldn't
happen often, but we can make no guarantees that previous passes didn't leave
dead code around.

llvm-svn: 229405
This commit is contained in:
James Molloy 2015-02-16 17:01:52 +00:00
parent e4359975ab
commit 382c1caece
2 changed files with 38 additions and 0 deletions
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2
lib/Transforms/Scalar/LoopRerollPass.cpp
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@ -511,6 +511,8 @@ void LoopReroll::SimpleLoopReduction::add(Loop *L) {
// (including the PHI), except for the last value (which is used by the PHI
// and also outside the loop).
Instruction *C = Instructions.front();
if (C->user_empty())
return;
do {
C = cast<Instruction>(*C->user_begin());

36
test/Transforms/LoopReroll/reduction.ll
View File

@ -92,5 +92,41 @@ for.end: ; preds = %for.body
ret float %add12
}
define i32 @foo_unusedphi(i32* nocapture readonly %x) #0 {
entry:
br label %for.body
for.body: ; preds = %entry, %for.body
%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
%r.029 = phi i32 [ 0, %entry ], [ %add12, %for.body ]
%arrayidx = getelementptr inbounds i32* %x, i64 %indvars.iv
%0 = load i32* %arrayidx, align 4
%add = add nsw i32 %0, %0
%1 = or i64 %indvars.iv, 1
%arrayidx3 = getelementptr inbounds i32* %x, i64 %1
%2 = load i32* %arrayidx3, align 4
%add4 = add nsw i32 %add, %2
%3 = or i64 %indvars.iv, 2
%arrayidx7 = getelementptr inbounds i32* %x, i64 %3
%4 = load i32* %arrayidx7, align 4
%add8 = add nsw i32 %add4, %4
%5 = or i64 %indvars.iv, 3
%arrayidx11 = getelementptr inbounds i32* %x, i64 %5
%6 = load i32* %arrayidx11, align 4
%add12 = add nsw i32 %add8, %6
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 4
%7 = trunc i64 %indvars.iv.next to i32
%cmp = icmp slt i32 %7, 400
br i1 %cmp, label %for.body, label %for.end
; CHECK-LABEL: @foo_unusedphi
; The above is just testing for a crash - no specific output expected.
; CHECK: ret
for.end: ; preds = %for.body
ret i32 %add12
}
attributes #0 = { nounwind readonly uwtable }