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SLP Vectorizer: Add support for vectorizing parts of the tree.

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Untill now we detected the vectorizable tree and evaluated the cost of the
entire tree.  With this patch we can decide to trim-out branches of the tree
that are not profitable to vectorizer.

Also, increase the max depth from 6 to 12. In the worse possible case where all
of the code is made of diamond-shaped graph this can bring the cost to 2**10,
but diamonds are not very common.

llvm-svn: 184681
This commit is contained in:
Nadav Rotem 2013-06-24 02:52:43 +00:00
parent 97a1d7c475
commit 210e86d7c4
2 changed files with 71 additions and 5 deletions
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30
llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
View File

@ -53,7 +53,7 @@ namespace {
static const unsigned MinVecRegSize = 128;
static const unsigned RecursionMaxDepth = 6;
static const unsigned RecursionMaxDepth = 12;
/// RAII pattern to save the insertion point of the IR builder.
class BuilderLocGuard {
@ -605,16 +605,17 @@ int FuncSLP::getTreeCost_rec(ArrayRef<Value *> VL, unsigned Depth) {
if (ScalarTy->isVectorTy())
return FuncSLP::MAX_COST;
VectorType *VecTy = VectorType::get(ScalarTy, VL.size());
if (allConstant(VL))
return 0;
VectorType *VecTy = VectorType::get(ScalarTy, VL.size());
if (isSplat(VL))
return TTI->getShuffleCost(TargetTransformInfo::SK_Broadcast, VecTy, 0);
int GatherCost = getGatherCost(VecTy);
if (Depth == RecursionMaxDepth || needToGatherAny(VL))
return getGatherCost(VecTy);
return GatherCost;
BasicBlock *BB = getSameBlock(VL);
unsigned Opcode = getSameOpcode(VL);
@ -677,6 +678,12 @@ int FuncSLP::getTreeCost_rec(ArrayRef<Value *> VL, unsigned Depth) {
VectorType *SrcVecTy = VectorType::get(SrcTy, VL.size());
int VecCost = TTI->getCastInstrCost(VL0->getOpcode(), VecTy, SrcVecTy);
Cost += (VecCost - ScalarCost);
if (Cost > GatherCost) {
MustGather.insert(VL.begin(), VL.end());
return GatherCost;
}
return Cost;
}
case Instruction::FCmp:
@ -739,6 +746,12 @@ int FuncSLP::getTreeCost_rec(ArrayRef<Value *> VL, unsigned Depth) {
VecCost = TTI->getArithmeticInstrCost(Opcode, VecTy);
}
TotalCost += (VecCost - ScalarCost);
if (TotalCost > GatherCost) {
MustGather.insert(VL.begin(), VL.end());
return GatherCost;
}
return TotalCost;
}
case Instruction::Load: {
@ -751,7 +764,14 @@ int FuncSLP::getTreeCost_rec(ArrayRef<Value *> VL, unsigned Depth) {
int ScalarLdCost = VecTy->getNumElements() *
TTI->getMemoryOpCost(Instruction::Load, ScalarTy, 1, 0);
int VecLdCost = TTI->getMemoryOpCost(Instruction::Load, ScalarTy, 1, 0);
return VecLdCost - ScalarLdCost;
int TotalCost = VecLdCost - ScalarLdCost;
if (TotalCost > GatherCost) {
MustGather.insert(VL.begin(), VL.end());
return GatherCost;
}
return TotalCost;
}
case Instruction::Store: {
// We know that we can merge the stores. Calculate the cost.

46
llvm/test/Transforms/SLPVectorizer/X86/long_chains.ll Normal file
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@ -0,0 +1,46 @@
; RUN: opt < %s -basicaa -slp-vectorizer -dce -S -mtriple=x86_64-apple-macosx10.8.0 -mcpu=corei7-avx | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.8.0"
; CHECK: test
; CHECK: sitofp i8
; CHECK-NEXT: sitofp i8
; CHECK-NEXT: insertelement
; CHECK-NEXT: insertelement
; CHECK-NEXT: fmul <2 x double>
; CHECK: ret
define i32 @test(double* nocapture %A, i8* nocapture %B) {
entry:
%0 = load i8* %B, align 1
%arrayidx1 = getelementptr inbounds i8* %B, i64 1
%1 = load i8* %arrayidx1, align 1
%add = add i8 %0, 3
%add4 = add i8 %1, 3
%conv6 = sitofp i8 %add to double
%conv7 = sitofp i8 %add4 to double ; <--- This is inefficient. The chain stops here.
%mul = fmul double %conv6, %conv6
%add8 = fadd double %mul, 1.000000e+00
%mul9 = fmul double %conv7, %conv7
%add10 = fadd double %mul9, 1.000000e+00
%mul11 = fmul double %add8, %add8
%add12 = fadd double %mul11, 1.000000e+00
%mul13 = fmul double %add10, %add10
%add14 = fadd double %mul13, 1.000000e+00
%mul15 = fmul double %add12, %add12
%add16 = fadd double %mul15, 1.000000e+00
%mul17 = fmul double %add14, %add14
%add18 = fadd double %mul17, 1.000000e+00
%mul19 = fmul double %add16, %add16
%add20 = fadd double %mul19, 1.000000e+00
%mul21 = fmul double %add18, %add18
%add22 = fadd double %mul21, 1.000000e+00
%mul23 = fmul double %add20, %add20
%add24 = fadd double %mul23, 1.000000e+00
%mul25 = fmul double %add22, %add22
%add26 = fadd double %mul25, 1.000000e+00
store double %add24, double* %A, align 8
%arrayidx28 = getelementptr inbounds double* %A, i64 1
store double %add26, double* %arrayidx28, align 8
ret i32 undef
}