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LoopVectorizer: Perform redundancy elimination on induction variables

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When the loop vectorizer was part of the SCC inliner pass manager gvn would
run after the loop vectorizer followed by instcombine. This way redundancy
(multiple uses) were removed and instcombine could perform scalarization on the
induction variables. Having moved the loop vectorizer to later we no longer run
any form of redundancy elimination before we perform instcombine. This caused
vectorized induction variables to survive that did not before.

On a recent iMac this helps linpack back from 6000Mflops to 7000Mflops.

This should also help lpbench and paq8p.

I ran a Release (without Asserts) build over the test-suite and did not see any
negative impact on compile time.

radar://15339680

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193891 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Arnold Schwaighofer 2013-11-01 22:18:19 +00:00
parent 4b1d68bca9
commit f4775827d0
4 changed files with 76 additions and 6 deletions
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35
lib/Transforms/Vectorize/LoopVectorize.cpp
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@ -2272,8 +2272,41 @@ InnerLoopVectorizer::vectorizeLoop(LoopVectorizationLegality *Legal) {
(RdxPhi)->setIncomingValue(SelfEdgeBlockIdx, ReducedPartRdx);
(RdxPhi)->setIncomingValue(IncomingEdgeBlockIdx, RdxDesc.LoopExitInstr);
}// end of for each redux variable.
fixLCSSAPHIs();
// Perform simple cse.
SmallPtrSet<Instruction*, 16> Visited;
SmallVector<Instruction*, 16> ToRemove;
for (BasicBlock::iterator I = LoopVectorBody->begin(),
E = LoopVectorBody->end(); I != E; ++I) {
Instruction *In = I;
if (!isa<InsertElementInst>(In) && !isa<ExtractElementInst>(In) &&
!isa<ShuffleVectorInst>(In) && !isa<GetElementPtrInst>(In))
continue;
// Check if we can replace this instruction with any of the
// visited instructions.
for (SmallPtrSet<Instruction*, 16>::iterator v = Visited.begin(),
ve = Visited.end(); v != ve; ++v) {
if (In->isIdenticalTo(*v)) {
In->replaceAllUsesWith(*v);
ToRemove.push_back(In);
In = 0;
break;
}
}
if (In)
Visited.insert(In);
}
// Erase all of the instructions that we RAUWed.
for (SmallVectorImpl<Instruction *>::iterator v = ToRemove.begin(),
ve = ToRemove.end(); v != ve; ++v) {
assert((*v)->getNumUses() == 0 && "Can't remove instructions with uses");
(*v)->eraseFromParent();
}
}
void InnerLoopVectorizer::fixLCSSAPHIs() {

7
test/Transforms/LoopVectorize/global_alias.ll
View File

@ -336,9 +336,8 @@ for.end: ; preds = %for.cond
; return Foo.A[a];
; }
; CHECK-LABEL: define i32 @noAlias07(
; CHECK: sub nsw <4 x i32>
; CHECK: store <4 x i32>
; CHECK: ret
define i32 @noAlias07(i32 %a) #0 {
entry:
%a.addr = alloca i32, align 4
@ -552,7 +551,7 @@ for.end: ; preds = %for.cond
; return Bar.A[N][a];
; }
; CHECK-LABEL: define i32 @noAlias11(
; CHECK: sub nsw <4 x i32>
; CHECK: store <4 x i32>
; CHECK: ret
define i32 @noAlias11(i32 %a) #0 {
@ -612,7 +611,7 @@ for.end: ; preds = %for.cond
; return Bar.A[N][a];
; }
; CHECK-LABEL: define i32 @noAlias12(
; CHECK: sub nsw <4 x i32>
; CHECK: store <4 x i32>
; CHECK: ret
define i32 @noAlias12(i32 %a) #0 {

38
test/Transforms/LoopVectorize/induction.ll
View File

@ -28,3 +28,41 @@ for.end:
ret void
}
; RUN: opt < %s -loop-vectorize -force-vector-unroll=1 -force-vector-width=2 -instcombine -S | FileCheck %s --check-prefix=IND
; Make sure we remove unneeded vectorization of induction variables.
; In order for instcombine to cleanup the vectorized induction variables that we
; create in the loop vectorizer we need to perform some form of redundancy
; elimination to get rid of multiple uses.
; IND-LABEL: scalar_use
; IND: br label %vector.body
; IND: vector.body:
; Vectorized induction variable.
; IND-NOT: insertelement <2 x i64>
; IND-NOT: shufflevector <2 x i64>
; IND: br {{.*}}, label %vector.body
define void @scalar_use(float* %a, float %b, i64 %offset, i64 %offset2, i64 %n) {
entry:
br label %for.body
for.body:
%iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
%ind.sum = add i64 %iv, %offset
%arr.idx = getelementptr inbounds float* %a, i64 %ind.sum
%l1 = load float* %arr.idx, align 4
%ind.sum2 = add i64 %iv, %offset2
%arr.idx2 = getelementptr inbounds float* %a, i64 %ind.sum2
%l2 = load float* %arr.idx2, align 4
%m = fmul fast float %b, %l2
%ad = fadd fast float %l1, %m
store float %ad, float* %arr.idx, align 4
%iv.next = add nuw nsw i64 %iv, 1
%exitcond = icmp eq i64 %iv.next, %n
br i1 %exitcond, label %loopexit, label %for.body
loopexit:
ret void
}

2
test/Transforms/LoopVectorize/induction_plus.ll
View File

@ -6,8 +6,8 @@ target triple = "x86_64-apple-macosx10.8.0"
@array = common global [1024 x i32] zeroinitializer, align 16
;CHECK-LABEL: @array_at_plus_one(
;CHECK: trunc i64
;CHECK: add i64 %index, 12
;CHECK: trunc i64
;CHECK: ret i32
define i32 @array_at_plus_one(i32 %n) nounwind uwtable ssp {
%1 = icmp sgt i32 %n, 0