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SLP Vectorizer: Add support for trees with external users.

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To support this we have to insert 'extractelement' instructions to pick the right lane.
We had this functionality before but I removed it when we moved to the multi-block design because it was too complicated.

llvm-svn: 185230
This commit is contained in:
Nadav Rotem 2013-06-28 22:07:09 +00:00
parent eeb1a667f6
commit 12c3b510fa
4 changed files with 259 additions and 30 deletions
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166
lib/Transforms/Vectorize/SLPVectorizer.cpp
View File

@ -221,6 +221,11 @@ public:
return false;
}
void forgetNumbering() {
for (Function::iterator it = F->begin(), e = F->end(); it != e; ++it)
BlocksNumbers[it].forget();
}
/// -- Vectorization State --
/// Maps values in the tree to the vector lanes that uses them. This map must
@ -243,9 +248,20 @@ public:
/// to stop cycles in the graph.
ValueSet VisitedPHIs;
/// Contains a list of values that are used outside the current tree. This
/// Contains a list of values that are used outside the current tree, the
/// first element in the bundle and the insertion point for extracts. This
/// set must be reset between runs.
SetVector<Value *> MultiUserVals;
struct UseInfo{
UseInfo(Instruction *VL0, int I) :
Leader(VL0), LastIndex(I) {}
UseInfo() : Leader(0), LastIndex(0) {}
/// The first element in the bundle.
Instruction *Leader;
/// The insertion index.
int LastIndex;
};
MapVector<Instruction*, UseInfo> MultiUserVals;
SetVector<Instruction*> ExtractedLane;
/// Holds all of the instructions that we gathered.
SetVector<Instruction *> GatherSeq;
@ -460,6 +476,7 @@ void FuncSLP::getTreeUses_rec(ArrayRef<Value *> VL, unsigned Depth) {
assert(VL0 && "Invalid instruction");
// Mark instructions with multiple users.
int LastIndex = getLastIndex(VL);
for (unsigned i = 0, e = VL.size(); i < e; ++i) {
if (PHINode *PN = dyn_cast<PHINode>(VL[i])) {
unsigned NumUses = 0;
@ -474,7 +491,8 @@ void FuncSLP::getTreeUses_rec(ArrayRef<Value *> VL, unsigned Depth) {
if (NumUses > 1) {
DEBUG(dbgs() << "SLP: Adding PHI to MultiUserVals "
"because it has " << NumUses << " users:" << *PN << " \n");
MultiUserVals.insert(PN);
UseInfo UI(VL0, 0);
MultiUserVals[PN] = UI;
}
continue;
}
@ -486,7 +504,8 @@ void FuncSLP::getTreeUses_rec(ArrayRef<Value *> VL, unsigned Depth) {
if (Depth && I && I->getNumUses() > 1) {
DEBUG(dbgs() << "SLP: Adding to MultiUserVals "
"because it has " << I->getNumUses() << " users:" << *I << " \n");
MultiUserVals.insert(I);
UseInfo UI(VL0, LastIndex);
MultiUserVals[I] = UI;
}
}
@ -678,6 +697,14 @@ int FuncSLP::getTreeCost_rec(ArrayRef<Value *> VL, unsigned Depth) {
}
}
// Calculate the extract cost.
unsigned ExternalUserExtractCost = 0;
for (unsigned i = 0, e = VL.size(); i < e; ++i)
if (ExtractedLane.count(cast<Instruction>(VL[i])))
ExternalUserExtractCost +=
TTI->getVectorInstrCost(Instruction::ExtractElement, VecTy, i);
Instruction *VL0 = cast<Instruction>(VL[0]);
switch (Opcode) {
case Instruction::PHI: {
@ -707,7 +734,7 @@ int FuncSLP::getTreeCost_rec(ArrayRef<Value *> VL, unsigned Depth) {
return GatherCost;
}
return TotalCost;
return TotalCost + ExternalUserExtractCost;
}
case Instruction::ExtractElement: {
if (CanReuseExtract(VL, VL.size(), VecTy))
@ -737,8 +764,8 @@ int FuncSLP::getTreeCost_rec(ArrayRef<Value *> VL, unsigned Depth) {
}
int Cost = getTreeCost_rec(Operands, Depth + 1);
if (Cost == FuncSLP::MAX_COST)
return Cost;
if (Cost == MAX_COST)
return MAX_COST;
// Calculate the cost of this instruction.
int ScalarCost = VL.size() * TTI->getCastInstrCost(VL0->getOpcode(),
@ -753,7 +780,7 @@ int FuncSLP::getTreeCost_rec(ArrayRef<Value *> VL, unsigned Depth) {
return GatherCost;
}
return Cost;
return Cost + ExternalUserExtractCost;
}
case Instruction::FCmp:
case Instruction::ICmp: {
@ -821,7 +848,7 @@ int FuncSLP::getTreeCost_rec(ArrayRef<Value *> VL, unsigned Depth) {
return GatherCost;
}
return TotalCost;
return TotalCost + ExternalUserExtractCost;
}
case Instruction::Load: {
// If we are scalarize the loads, add the cost of forming the vector.
@ -840,7 +867,7 @@ int FuncSLP::getTreeCost_rec(ArrayRef<Value *> VL, unsigned Depth) {
return GatherCost;
}
return TotalCost;
return TotalCost + ExternalUserExtractCost;
}
case Instruction::Store: {
// We know that we can merge the stores. Calculate the cost.
@ -860,7 +887,7 @@ int FuncSLP::getTreeCost_rec(ArrayRef<Value *> VL, unsigned Depth) {
return MAX_COST;
int TotalCost = StoreCost + Cost;
return TotalCost;
return TotalCost + ExternalUserExtractCost;
}
default:
// Unable to vectorize unknown instructions.
@ -874,6 +901,7 @@ int FuncSLP::getTreeCost(ArrayRef<Value *> VL) {
MemBarrierIgnoreList.clear();
LaneMap.clear();
MultiUserVals.clear();
ExtractedLane.clear();
MustGather.clear();
VisitedPHIs.clear();
@ -893,21 +921,58 @@ int FuncSLP::getTreeCost(ArrayRef<Value *> VL) {
// must be scalarized.
getTreeUses_rec(VL, 0);
// Check that instructions with multiple users can be vectorized. Mark unsafe
// instructions.
for (SetVector<Value *>::iterator it = MultiUserVals.begin(),
e = MultiUserVals.end();
it != e; ++it) {
// Check that instructions with multiple users can be vectorized. Mark
// unsafe instructions.
for (MapVector<Instruction *, UseInfo>::iterator UI = MultiUserVals.begin(),
e = MultiUserVals.end(); UI != e; ++UI) {
Instruction *Scalar = UI->first;
if (MustGather.count(Scalar))
continue;
assert(LaneMap.count(Scalar) && "Unknown scalar");
int ScalarLane = LaneMap[Scalar];
bool ExternalUse = false;
// Check that all of the users of this instr are within the tree.
for (Value::use_iterator I = (*it)->use_begin(), E = (*it)->use_end();
I != E; ++I) {
if (LaneMap.find(*I) == LaneMap.end()) {
DEBUG(dbgs() << "SLP: Adding to MustExtract "
"because of an out of tree usage.\n");
MustGather.insert(*it);
for (Value::use_iterator Usr = Scalar->use_begin(),
UE = Scalar->use_end(); Usr != UE; ++Usr) {
// If this user is within the tree, make sure it is from the same lane.
// Notice that we have both in-tree and out-of-tree users.
if (LaneMap.count(*Usr)) {
if (LaneMap[*Usr] != ScalarLane) {
DEBUG(dbgs() << "SLP: Adding to MustExtract "
"because of an out-of-lane usage.\n");
MustGather.insert(Scalar);
break;
}
continue;
}
// We have an out-of-tree user. Check if we can place an 'extract'.
Instruction *User = cast<Instruction>(*Usr);
// We care about the order only if the user is in the same block.
if (User->getParent() == Scalar->getParent()) {
int LastLoc = UI->second.LastIndex;
BlockNumbering &BN = BlocksNumbers[User->getParent()];
int UserIdx = BN.getIndex(User);
if (UserIdx <= LastLoc) {
DEBUG(dbgs() << "SLP: Adding to MustExtract because of an external "
"user that we can't schedule.\n");
MustGather.insert(Scalar);
break;
}
}
// We have an external user.
ExternalUse = true;
}
if (ExternalUse) {
// Items that are left in MultiUserVals are to be extracted.
// ExtractLane is used for the lookup.
ExtractedLane.insert(Scalar);
}
}
// Now calculate the cost of vectorizing the tree.
@ -1238,10 +1303,58 @@ Value *FuncSLP::vectorizeTree(ArrayRef<Value *> VL) {
Builder.SetInsertPoint(getLastInstruction(VL));
Value *V = vectorizeTree_rec(VL);
DEBUG(dbgs() << "SLP: Placing 'extracts'\n");
for (SetVector<Instruction*>::iterator it = ExtractedLane.begin(), e =
ExtractedLane.end(); it != e; ++it) {
Instruction *Scalar = *it;
DEBUG(dbgs() << "SLP: Looking at " << *Scalar);
if (!Scalar)
continue;
Instruction *Loc = 0;
assert(MultiUserVals.count(Scalar) && "Can't find the lane to extract");
Instruction *Leader = MultiUserVals[Scalar].Leader;
// This value is gathered so we don't need to extract from anywhere.
if (!VectorizedValues.count(Leader))
continue;
Value *Vec = VectorizedValues[Leader];
if (PHINode *PN = dyn_cast<PHINode>(Vec)) {
Loc = PN->getParent()->getFirstInsertionPt();
} else {
Instruction *I = cast<Instruction>(Vec);
BasicBlock::iterator L = *I;
Loc = ++L;
}
Builder.SetInsertPoint(Loc);
assert(LaneMap.count(Scalar) && "Can't find the extracted lane.");
int Lane = LaneMap[Scalar];
Value *Idx = Builder.getInt32(Lane);
Value *Extract = Builder.CreateExtractElement(Vec, Idx);
bool Replaced = false;;
for (Value::use_iterator U = Scalar->use_begin(), UE = Scalar->use_end();
U != UE; ++U) {
Instruction *UI = cast<Instruction>(*U);
// No need to replace instructions that are inside our lane map.
if (LaneMap.count(UI))
continue;
UI->replaceUsesOfWith(Scalar ,Extract);
Replaced = true;
}
assert(Replaced && "Must replace at least one outside user");
(void)Replaced;
}
// We moved some instructions around. We have to number them again
// before we can do any analysis.
for (Function::iterator it = F->begin(), e = F->end(); it != e; ++it)
BlocksNumbers[it].forget();
forgetNumbering();
// Clear the state.
MustGather.clear();
VisitedPHIs.clear();
@ -1251,15 +1364,18 @@ Value *FuncSLP::vectorizeTree(ArrayRef<Value *> VL) {
}
Value *FuncSLP::vectorizeArith(ArrayRef<Value *> Operands) {
Instruction *LastInst = getLastInstruction(Operands);
Value *Vec = vectorizeTree(Operands);
// After vectorizing the operands we need to generate extractelement
// instructions and replace all of the uses of the scalar values with
// the values that we extracted from the vectorized tree.
Builder.SetInsertPoint(LastInst);
for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
Value *S = Builder.CreateExtractElement(Vec, Builder.getInt32(i));
Operands[i]->replaceAllUsesWith(S);
}
forgetNumbering();
return Vec;
}
@ -1334,6 +1450,8 @@ void FuncSLP::optimizeGatherSequence() {
assert((*v)->getNumUses() == 0 && "Can't remove instructions with uses");
(*v)->eraseFromParent();
}
forgetNumbering();
}
/// The SLPVectorizer Pass.

11
test/Transforms/SLPVectorizer/X86/cse.ll
View File

@ -11,13 +11,12 @@ target triple = "i386-apple-macosx10.8.0"
;}
;CHECK: @test
;CHECK: insertelement <2 x double> undef
;CHECK-NEXT: insertelement <2 x double>
;CHECK-NEXT: fadd <2 x double>
;CHECK: load <2 x double>
;CHECK: fadd <2 x double>
;CHECK: store <2 x double>
;CHECK: insertelement <2 x double>
;CHECK: fadd <2 x double>
;CHECK: store <2 x double>
;CHECK: insertelement <2 x double>
;CHECK-NEXT: fadd <2 x double>
;CHECK: store <2 x double>
;CHECK: ret i32
define i32 @test(double* nocapture %G) {

61
test/Transforms/SLPVectorizer/X86/external_user.ll Normal file
View File

@ -0,0 +1,61 @@
; 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"
; double foo(double * restrict b, double * restrict a, int n, int m) {
; double r=a[1];
; double g=a[0];
; double x;
; for (int i=0; i < 100; i++) {
; r += 10;
; g += 10;
; r *= 4;
; g *= 4;
; x = g; <----- external user!
; r += 4;
; g += 4;
; }
; b[0] = g;
; b[1] = r;
;
; return x; <-- must extract here!
; }
;CHECK: ext_user
;CHECK: phi <2 x double>
;CHECK: fadd <2 x double>
;CHECK: fmul <2 x double>
;CHECK: extractelement <2 x double>
;CHECK: br
;CHECK: store <2 x double>
;CHECK: ret double
define double @ext_user(double* noalias nocapture %B, double* noalias nocapture %A, i32 %n, i32 %m) {
entry:
%arrayidx = getelementptr inbounds double* %A, i64 1
%0 = load double* %arrayidx, align 8
%1 = load double* %A, align 8
br label %for.body
for.body: ; preds = %for.body, %entry
%i.020 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
%G.019 = phi double [ %1, %entry ], [ %add5, %for.body ]
%R.018 = phi double [ %0, %entry ], [ %add4, %for.body ]
%add = fadd double %R.018, 1.000000e+01
%add2 = fadd double %G.019, 1.000000e+01
%mul = fmul double %add, 4.000000e+00
%mul3 = fmul double %add2, 4.000000e+00
%add4 = fadd double %mul, 4.000000e+00
%add5 = fadd double %mul3, 4.000000e+00
%inc = add nsw i32 %i.020, 1
%exitcond = icmp eq i32 %inc, 100
br i1 %exitcond, label %for.end, label %for.body
for.end: ; preds = %for.body
store double %add5, double* %B, align 8
%arrayidx7 = getelementptr inbounds double* %B, i64 1
store double %add4, double* %arrayidx7, align 8
ret double %mul3
}

51
test/Transforms/SLPVectorizer/X86/phi.ll
View File

@ -44,3 +44,54 @@ if.end: ; preds = %entry, %if.else
ret i32 undef
}
;int foo(double * restrict B, double * restrict A, int n, int m) {
; double R=A[1];
; double G=A[0];
; for (int i=0; i < 100; i++) {
; R += 10;
; G += 10;
; R *= 4;
; G *= 4;
; R += 4;
; G += 4;
; }
; B[0] = G;
; B[1] = R;
; return 0;
;}
;CHECK: foo2
;CHECK: load <2 x double>
;CHECK: phi <2 x double>
;CHECK: fmul <2 x double>
;CHECK: store <2 x double>
;CHECK: ret
define i32 @foo2(double* noalias nocapture %B, double* noalias nocapture %A, i32 %n, i32 %m) #0 {
entry:
%arrayidx = getelementptr inbounds double* %A, i64 1
%0 = load double* %arrayidx, align 8
%1 = load double* %A, align 8
br label %for.body
for.body: ; preds = %for.body, %entry
%i.019 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
%G.018 = phi double [ %1, %entry ], [ %add5, %for.body ]
%R.017 = phi double [ %0, %entry ], [ %add4, %for.body ]
%add = fadd double %R.017, 1.000000e+01
%add2 = fadd double %G.018, 1.000000e+01
%mul = fmul double %add, 4.000000e+00
%mul3 = fmul double %add2, 4.000000e+00
%add4 = fadd double %mul, 4.000000e+00
%add5 = fadd double %mul3, 4.000000e+00
%inc = add nsw i32 %i.019, 1
%exitcond = icmp eq i32 %inc, 100
br i1 %exitcond, label %for.end, label %for.body
for.end: ; preds = %for.body
store double %add5, double* %B, align 8
%arrayidx7 = getelementptr inbounds double* %B, i64 1
store double %add4, double* %arrayidx7, align 8
ret i32 0
}