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[LV] Relax Small Size Reduction Type Requirement

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This patch enables small size reductions in which the source types are smaller
than the reduction type (e.g., computing an i16 sum from the values in an i8
array). The previous behavior was to only allow small size reductions if the
source types and reduction type were the same. The change accounts for the fact
that the existing sign- and zero-extend instructions in these cases should
still be included in the cost model.

Differential Revision: http://reviews.llvm.org/D12770

llvm-svn: 247337
This commit is contained in:
Matthew Simpson 2015-09-10 21:12:57 +00:00
parent 4707066140
commit 154abb5d70
2 changed files with 80 additions and 9 deletions
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20
lib/Transforms/Utils/LoopUtils.cpp
View File

@ -98,6 +98,7 @@ bool RecurrenceDescriptor::getSourceExtensionKind(
SmallVector<Instruction *, 8> Worklist;
bool FoundOneOperand = false;
unsigned DstSize = RT->getPrimitiveSizeInBits();
Worklist.push_back(Exit);
// Traverse the instructions in the reduction expression, beginning with the
@ -120,11 +121,16 @@ bool RecurrenceDescriptor::getSourceExtensionKind(
// If the operand is not in Visited, it is not a reduction operation, but
// it does feed into one. Make sure it is either a single-use sign- or
// zero-extend of the recurrence type.
// zero-extend instruction.
CastInst *Cast = dyn_cast<CastInst>(J);
bool IsSExtInst = isa<SExtInst>(J);
if (!Cast || !Cast->hasOneUse() || Cast->getSrcTy() != RT ||
!(isa<ZExtInst>(J) || IsSExtInst))
if (!Cast || !Cast->hasOneUse() || !(isa<ZExtInst>(J) || IsSExtInst))
return false;
// Ensure the source type of the extend is no larger than the reduction
// type. It is not necessary for the types to be identical.
unsigned SrcSize = Cast->getSrcTy()->getPrimitiveSizeInBits();
if (SrcSize > DstSize)
return false;
// Furthermore, ensure that all such extends are of the same kind.
@ -136,9 +142,11 @@ bool RecurrenceDescriptor::getSourceExtensionKind(
IsSigned = IsSExtInst;
}
// Lastly, add the sign- or zero-extend to CI so that we can avoid
// accounting for it in the cost model.
CI.insert(Cast);
// Lastly, if the source type of the extend matches the reduction type,
// add the extend to CI so that we can avoid accounting for it in the
// cost model.
if (SrcSize == DstSize)
CI.insert(Cast);
}
}
return true;

69
test/Transforms/LoopVectorize/AArch64/reduction-small-size.ll
View File

@ -66,9 +66,9 @@ for.body:
br i1 %exitcond, label %for.cond.for.cond.cleanup_crit_edge, label %for.body
}
; CHECK-LABEL: @reduction_i16
; CHECK-LABEL: @reduction_i16_1
;
; short reduction_i16(short *a, short *b, int n) {
; short reduction_i16_1(short *a, short *b, int n) {
; short sum = 0;
; for (int i = 0; i < n; ++i)
; sum += (a[i] + b[i]);
@ -92,7 +92,7 @@ for.body:
; CHECK: [[Rdx:%[a-zA-Z0-9.]+]] = extractelement <8 x i16>
; CHECK: zext i16 [[Rdx]] to i32
;
define i16 @reduction_i16(i16* nocapture readonly %a, i16* nocapture readonly %b, i32 %n) {
define i16 @reduction_i16_1(i16* nocapture readonly %a, i16* nocapture readonly %b, i32 %n) {
entry:
%cmp.16 = icmp sgt i32 %n, 0
br i1 %cmp.16, label %for.body.preheader, label %for.cond.cleanup
@ -126,3 +126,66 @@ for.body:
%exitcond = icmp eq i32 %lftr.wideiv, %n
br i1 %exitcond, label %for.cond.for.cond.cleanup_crit_edge, label %for.body
}
; CHECK-LABEL: @reduction_i16_2
;
; short reduction_i16_2(char *a, char *b, int n) {
; short sum = 0;
; for (int i = 0; i < n; ++i)
; sum += (a[i] + b[i]);
; return sum;
; }
;
; CHECK: vector.body:
; CHECK: phi <8 x i16>
; CHECK: [[Ld1:%[a-zA-Z0-9.]+]] = load <8 x i8>
; CHECK: zext <8 x i8> [[Ld1]] to <8 x i16>
; CHECK: [[Ld2:%[a-zA-Z0-9.]+]] = load <8 x i8>
; CHECK: zext <8 x i8> [[Ld2]] to <8 x i16>
; CHECK: add <8 x i16>
; CHECK: add <8 x i16>
;
; CHECK: middle.block:
; CHECK: shufflevector <8 x i16>
; CHECK: add <8 x i16>
; CHECK: shufflevector <8 x i16>
; CHECK: add <8 x i16>
; CHECK: shufflevector <8 x i16>
; CHECK: add <8 x i16>
; CHECK: [[Rdx:%[a-zA-Z0-9.]+]] = extractelement <8 x i16>
; CHECK: zext i16 [[Rdx]] to i32
;
define i16 @reduction_i16_2(i8* nocapture readonly %a, i8* nocapture readonly %b, i32 %n) {
entry:
%cmp.14 = icmp sgt i32 %n, 0
br i1 %cmp.14, label %for.body.preheader, label %for.cond.cleanup
for.body.preheader:
br label %for.body
for.cond.for.cond.cleanup_crit_edge:
%add5.lcssa = phi i32 [ %add5, %for.body ]
%conv6 = trunc i32 %add5.lcssa to i16
br label %for.cond.cleanup
for.cond.cleanup:
%sum.0.lcssa = phi i16 [ %conv6, %for.cond.for.cond.cleanup_crit_edge ], [ 0, %entry ]
ret i16 %sum.0.lcssa
for.body:
%indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %for.body.preheader ]
%sum.015 = phi i32 [ %add5, %for.body ], [ 0, %for.body.preheader ]
%arrayidx = getelementptr inbounds i8, i8* %a, i64 %indvars.iv
%0 = load i8, i8* %arrayidx, align 1
%conv = zext i8 %0 to i32
%arrayidx2 = getelementptr inbounds i8, i8* %b, i64 %indvars.iv
%1 = load i8, i8* %arrayidx2, align 1
%conv3 = zext i8 %1 to i32
%conv4.13 = and i32 %sum.015, 65535
%add = add nuw nsw i32 %conv, %conv4.13
%add5 = add nuw nsw i32 %add, %conv3
%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, %n
br i1 %exitcond, label %for.cond.for.cond.cleanup_crit_edge, label %for.body
}