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[VectorUtils] Don't try and truncate PHIs to a smaller bitwidth

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We already try not to truncate PHIs in computeMinimalBitwidths. LoopVectorize can't handle it and we really don't need to, because both induction and reduction PHIs are truncated by other means.

However, we weren't bailing out in all the places we should have, and we ended up by returning a PHI to be truncated, which has caused PR27018.

This fixes PR17018.

llvm-svn: 264852
This commit is contained in:
James Molloy 2016-03-30 10:11:43 +00:00
parent 0c67e1a699
commit 7bcc6040d2
2 changed files with 73 additions and 0 deletions
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15
lib/Analysis/VectorUtils.cpp
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@ -499,6 +499,7 @@ llvm::computeMinimumValueSizes(ArrayRef<BasicBlock *> Blocks, DemandedBits &DB,
uint64_t V = DB.getDemandedBits(I).getZExtValue();
DBits[Leader] |= V;
DBits[I] = V;
// Casts, loads and instructions outside of our range terminate a chain
// successfully.
@ -549,6 +550,20 @@ llvm::computeMinimumValueSizes(ArrayRef<BasicBlock *> Blocks, DemandedBits &DB,
// Round up to a power of 2
if (!isPowerOf2_64((uint64_t)MinBW))
MinBW = NextPowerOf2(MinBW);
// We don't modify the types of PHIs. Reductions will already have been
// truncated if possible, and inductions' sizes will have been chosen by
// indvars.
// If we are required to shrink a PHI, abandon this entire equivalence class.
bool Abort = false;
for (auto MI = ECs.member_begin(I), ME = ECs.member_end(); MI != ME; ++MI)
if (isa<PHINode>(*MI) && MinBW < (*MI)->getType()->getScalarSizeInBits()) {
Abort = true;
break;
}
if (Abort)
continue;
for (auto MI = ECs.member_begin(I), ME = ECs.member_end(); MI != ME; ++MI) {
if (!isa<Instruction>(*MI))
continue;

58
test/Transforms/LoopVectorize/AArch64/loop-vectorization-factors.ll
View File

@ -205,5 +205,63 @@ for.body: ; preds = %for.body, %for.body
br i1 %exitcond, label %for.cond.cleanup, label %for.body
}
; CHECK-LABEL: @add_phifail(
; CHECK: load <16 x i8>, <16 x i8>*
; CHECK: add nuw nsw <16 x i32>
; CHECK: store <16 x i8>
; Function Attrs: nounwind
define void @add_phifail(i8* noalias nocapture readonly %p, i8* noalias nocapture %q, i32 %len) #0 {
entry:
%cmp8 = icmp sgt i32 %len, 0
br i1 %cmp8, label %for.body, label %for.cond.cleanup
for.cond.cleanup: ; preds = %for.body, %entry
ret void
for.body: ; preds = %entry, %for.body
%indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
%a_phi = phi i32 [ %conv, %for.body ], [ 0, %entry ]
%arrayidx = getelementptr inbounds i8, i8* %p, i64 %indvars.iv
%0 = load i8, i8* %arrayidx
%conv = zext i8 %0 to i32
%add = add nuw nsw i32 %conv, 2
%conv1 = trunc i32 %add to i8
%arrayidx3 = getelementptr inbounds i8, i8* %q, i64 %indvars.iv
store i8 %conv1, i8* %arrayidx3
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%lftr.wideiv = trunc i64 %indvars.iv.next to i32
%exitcond = icmp eq i32 %lftr.wideiv, %len
br i1 %exitcond, label %for.cond.cleanup, label %for.body
}
; CHECK-LABEL: @add_phifail2(
; CHECK: load <16 x i8>, <16 x i8>*
; CHECK: add nuw nsw <16 x i32>
; CHECK: store <16 x i8>
; Function Attrs: nounwind
define i8 @add_phifail2(i8* noalias nocapture readonly %p, i8* noalias nocapture %q, i32 %len) #0 {
entry:
br label %for.body
for.cond.cleanup: ; preds = %for.body, %entry
%ret = trunc i32 %a_phi to i8
ret i8 %ret
for.body: ; preds = %entry, %for.body
%indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
%a_phi = phi i32 [ %conv, %for.body ], [ 0, %entry ]
%arrayidx = getelementptr inbounds i8, i8* %p, i64 %indvars.iv
%0 = load i8, i8* %arrayidx
%conv = zext i8 %0 to i32
%add = add nuw nsw i32 %conv, 2
%conv1 = trunc i32 %add to i8
%arrayidx3 = getelementptr inbounds i8, i8* %q, i64 %indvars.iv
store i8 %conv1, i8* %arrayidx3
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%lftr.wideiv = trunc i64 %indvars.iv.next to i32
%exitcond = icmp eq i32 %lftr.wideiv, %len
br i1 %exitcond, label %for.cond.cleanup, label %for.body
}
attributes #0 = { nounwind }