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[LV] Considier non-consecutive but vectorizable accesses for VF selection

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When computing the smallest and largest types for selecting the maximum
vectorization factor, we currently ignore loads and stores of pointer types if
the memory access is non-consecutive. We do this because such accesses must be
scalarized regardless of vectorization factor, and thus shouldn't be considered
when determining the factor. This patch makes this check less aggressive by
also considering non-consecutive accesses that may be vectorized, such as
interleaved accesses. Because we don't know at the time of the check if an
accesses will certainly be vectorized (this is a cost model decision given a
particular VF), we consider all accesses that can potentially be vectorized.

Differential Revision: https://reviews.llvm.org/D30305

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296747 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matthew Simpson 2017-03-02 13:55:05 +00:00
parent 3a93c4ad6c
commit 465f5a16f9
2 changed files with 43 additions and 3 deletions
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13
lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@ -6326,9 +6326,16 @@ LoopVectorizationCostModel::getSmallestAndWidestTypes() {
T = ST->getValueOperand()->getType(); T = ST->getValueOperand()->getType();
// Ignore loaded pointer types and stored pointer types that are not // Ignore loaded pointer types and stored pointer types that are not
// consecutive. However, we do want to take consecutive stores/loads of // vectorizable.
// pointer vectors into account. //
if (T->isPointerTy() && !isConsecutiveLoadOrStore(&I)) // FIXME: The check here attempts to predict whether a load or store will
// be vectorized. We only know this for certain after a VF has
// been selected. Here, we assume that if an access can be
// vectorized, it will be. We should also look at extending this
// optimization to non-pointer types.
//
if (T->isPointerTy() && !isConsecutiveLoadOrStore(&I) &&
!Legal->isAccessInterleaved(&I) && !Legal->isLegalGatherOrScatter(&I))
continue; continue;
MinWidth = std::min(MinWidth, MinWidth = std::min(MinWidth,

33
test/Transforms/LoopVectorize/AArch64/smallest-and-widest-types.ll Normal file
View File

@ -0,0 +1,33 @@
; REQUIRES: asserts
; RUN: opt < %s -loop-vectorize -debug-only=loop-vectorize -disable-output 2>&1 | FileCheck %s
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64--linux-gnu"
; CHECK-LABEL: Checking a loop in "interleaved_access"
; CHECK: The Smallest and Widest types: 64 / 64 bits
;
define void @interleaved_access(i8** %A, i64 %N) {
for.ph:
br label %for.body
for.body:
%i = phi i64 [ %i.next.3, %for.body ], [ 0, %for.ph ]
%tmp0 = getelementptr inbounds i8*, i8** %A, i64 %i
store i8* null, i8** %tmp0, align 8
%i.next.0 = add nuw nsw i64 %i, 1
%tmp1 = getelementptr inbounds i8*, i8** %A, i64 %i.next.0
store i8* null, i8** %tmp1, align 8
%i.next.1 = add nsw i64 %i, 2
%tmp2 = getelementptr inbounds i8*, i8** %A, i64 %i.next.1
store i8* null, i8** %tmp2, align 8
%i.next.2 = add nsw i64 %i, 3
%tmp3 = getelementptr inbounds i8*, i8** %A, i64 %i.next.2
store i8* null, i8** %tmp3, align 8
%i.next.3 = add nsw i64 %i, 4
%cond = icmp slt i64 %i.next.3, %N
br i1 %cond, label %for.body, label %for.end
for.end:
ret void
}