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teach reassociate to factor x+x+x -> x*3. While I'm at it,

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fix RemoveDeadBinaryOp to actually do something.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92368 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-12-31 19:24:52 +00:00
parent 9f7b7089be
commit 69e98e2c0f
2 changed files with 102 additions and 32 deletions
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92
lib/Transforms/Scalar/Reassociate.cpp
View File

@ -88,7 +88,7 @@ namespace {
private:
void BuildRankMap(Function &F);
unsigned getRank(Value *V);
void ReassociateExpression(BinaryOperator *I);
Value *ReassociateExpression(BinaryOperator *I);
void RewriteExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops,
unsigned Idx = 0);
Value *OptimizeExpression(BinaryOperator *I,
@ -111,10 +111,13 @@ FunctionPass *llvm::createReassociatePass() { return new Reassociate(); }
void Reassociate::RemoveDeadBinaryOp(Value *V) {
Instruction *Op = dyn_cast<Instruction>(V);
if (!Op || !isa<BinaryOperator>(Op) || !isa<CmpInst>(Op) || !Op->use_empty())
if (!Op || !isa<BinaryOperator>(Op) || !Op->use_empty())
return;
Value *LHS = Op->getOperand(0), *RHS = Op->getOperand(1);
ValueRankMap.erase(Op);
Op->eraseFromParent();
RemoveDeadBinaryOp(LHS);
RemoveDeadBinaryOp(RHS);
}
@ -602,15 +605,57 @@ static Value *OptimizeAndOrXor(unsigned Opcode,
/// is returned, otherwise the Ops list is mutated as necessary.
Value *Reassociate::OptimizeAdd(Instruction *I,
SmallVectorImpl<ValueEntry> &Ops) {
SmallPtrSet<Value*, 8> OperandsSeen;
Restart:
OperandsSeen.clear();
// Scan the operand lists looking for X and -X pairs. If we find any, we
// can simplify the expression. X+-X == 0.
// can simplify the expression. X+-X == 0. While we're at it, scan for any
// duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
assert(i < Ops.size());
Value *TheOp = Ops[i].Op;
// Check to see if we've seen this operand before. If so, we factor all
// instances of the operand together.
if (!OperandsSeen.insert(TheOp)) {
// Rescan the list, removing all instances of this operand from the expr.
unsigned NumFound = 0;
for (unsigned j = 0, je = Ops.size(); j != je; ++j) {
if (Ops[j].Op != TheOp) continue;
++NumFound;
Ops.erase(Ops.begin()+j);
--j; --je;
}
/*DEBUG*/(errs() << "\nFACTORING [" << NumFound << "]: " << *TheOp << '\n');
++NumFactor;
// Insert a new multiply.
Value *Mul = ConstantInt::get(cast<IntegerType>(I->getType()), NumFound);
Mul = BinaryOperator::CreateMul(TheOp, Mul, "factor", I);
// Now that we have inserted a multiply, optimize it. This allows us to
// handle cases that require multiple factoring steps, such as this:
// (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6
Mul = ReassociateExpression(cast<BinaryOperator>(Mul));
// If every add operand was a duplicate, return the multiply.
if (Ops.empty())
return Mul;
// Otherwise, we had some input that didn't have the dupe, such as
// "A + A + B" -> "A*2 + B". Add the new multiply to the list of
// things being added by this operation.
Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul));
goto Restart;
}
// Check for X and -X in the operand list.
if (!BinaryOperator::isNeg(Ops[i].Op))
if (!BinaryOperator::isNeg(TheOp))
continue;
Value *X = BinaryOperator::getNegArgument(Ops[i].Op);
Value *X = BinaryOperator::getNegArgument(TheOp);
unsigned FoundX = FindInOperandList(Ops, i, X);
if (FoundX == i)
continue;
@ -639,7 +684,6 @@ Value *Reassociate::OptimizeAdd(Instruction *I,
// Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4)
// where they are actually the same multiply.
SmallPtrSet<BinaryOperator*, 4> Multiplies;
unsigned MaxOcc = 0;
Value *MaxOccVal = 0;
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
@ -647,9 +691,6 @@ Value *Reassociate::OptimizeAdd(Instruction *I,
if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty())
continue;
// If we've already seen this multiply, don't revisit it.
if (!Multiplies.insert(BOp)) continue;
// Compute all of the factors of this added value.
SmallVector<Value*, 8> Factors;
FindSingleUseMultiplyFactors(BOp, Factors);
@ -676,7 +717,7 @@ Value *Reassociate::OptimizeAdd(Instruction *I,
// If any factor occurred more than one time, we can pull it out.
if (MaxOcc > 1) {
DEBUG(errs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << "\n");
DEBUG(errs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << '\n');
++NumFactor;
// Create a new instruction that uses the MaxOccVal twice. If we don't do
@ -698,13 +739,17 @@ Value *Reassociate::OptimizeAdd(Instruction *I,
unsigned NumAddedValues = NewMulOps.size();
Value *V = EmitAddTreeOfValues(I, NewMulOps);
Value *V2 = BinaryOperator::CreateMul(V, MaxOccVal, "tmp", I);
// Now that we have inserted V and its sole use, optimize it. This allows
// us to handle cases that require multiple factoring steps, such as this:
// Now that we have inserted the add tree, optimize it. This allows us to
// handle cases that require multiple factoring steps, such as this:
// A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
assert(NumAddedValues > 1 && "Each occurrence should contribute a value");
ReassociateExpression(cast<BinaryOperator>(V));
V = ReassociateExpression(cast<BinaryOperator>(V));
// Create the multiply.
Value *V2 = BinaryOperator::CreateMul(V, MaxOccVal, "tmp", I);
// FIXME: Should rerun 'ReassociateExpression' on the mul too??
// If every add operand included the factor (e.g. "A*B + A*C"), then the
// entire result expression is just the multiply "A*(B+C)".
@ -852,9 +897,10 @@ void Reassociate::ReassociateBB(BasicBlock *BB) {
}
}
void Reassociate::ReassociateExpression(BinaryOperator *I) {
Value *Reassociate::ReassociateExpression(BinaryOperator *I) {
// First, walk the expression tree, linearizing the tree, collecting
// First, walk the expression tree, linearizing the tree, collecting the
// operand information.
SmallVector<ValueEntry, 8> Ops;
LinearizeExprTree(I, Ops);
@ -877,7 +923,7 @@ void Reassociate::ReassociateExpression(BinaryOperator *I) {
I->replaceAllUsesWith(V);
RemoveDeadBinaryOp(I);
++NumAnnihil;
return;
return V;
}
// We want to sink immediates as deeply as possible except in the case where
@ -899,11 +945,13 @@ void Reassociate::ReassociateExpression(BinaryOperator *I) {
// eliminate it.
I->replaceAllUsesWith(Ops[0].Op);
RemoveDeadBinaryOp(I);
} else {
// Now that we ordered and optimized the expressions, splat them back into
// the expression tree, removing any unneeded nodes.
RewriteExprTree(I, Ops);
return Ops[0].Op;
}
// Now that we ordered and optimized the expressions, splat them back into
// the expression tree, removing any unneeded nodes.
RewriteExprTree(I, Ops);
return I;
}

42
test/Transforms/Reassociate/basictest.ll
View File

@ -88,19 +88,19 @@ define void @test5() {
}
define i32 @test6() {
%tmp.0 = load i32* @a ; <i32> [#uses=2]
%tmp.1 = load i32* @b ; <i32> [#uses=2]
%tmp.0 = load i32* @a
%tmp.1 = load i32* @b
; (a+b)
%tmp.2 = add i32 %tmp.0, %tmp.1 ; <i32> [#uses=1]
%tmp.4 = load i32* @c ; <i32> [#uses=2]
%tmp.2 = add i32 %tmp.0, %tmp.1
%tmp.4 = load i32* @c
; (a+b)+c
%tmp.5 = add i32 %tmp.2, %tmp.4 ; <i32> [#uses=1]
%tmp.5 = add i32 %tmp.2, %tmp.4
; (a+c)
%tmp.8 = add i32 %tmp.0, %tmp.4 ; <i32> [#uses=1]
%tmp.8 = add i32 %tmp.0, %tmp.4
; (a+c)+b
%tmp.11 = add i32 %tmp.8, %tmp.1 ; <i32> [#uses=1]
%tmp.11 = add i32 %tmp.8, %tmp.1
; X ^ X = 0
%RV = xor i32 %tmp.5, %tmp.11 ; <i32> [#uses=1]
%RV = xor i32 %tmp.5, %tmp.11
ret i32 %RV
; CHECK: @test6
; CHECK: ret i32 0
@ -108,6 +108,7 @@ define i32 @test6() {
; This should be one add and two multiplies.
define i32 @test7(i32 %A, i32 %B, i32 %C) {
; A*A*B + A*C*A
%aa = mul i32 %A, %A
%aab = mul i32 %aa, %B
%ac = mul i32 %A, %C
@ -141,6 +142,27 @@ define i32 @test9(i32 %X) {
%Z = add i32 %Y, %Y
ret i32 %Z
; CHECK: @test9
; CHECK-NEXT: %Z = mul i32 %X, 94
; CHECK-NEXT: ret i32 %Z
; CHECK-NEXT: mul i32 %X, 94
; CHECK-NEXT: ret i32
}
define i32 @test10(i32 %X) {
%Y = add i32 %X ,%X
%Z = add i32 %Y, %X
ret i32 %Z
; CHECK: @test10
; CHECK-NEXT: mul i32 %X, 3
; CHECK-NEXT: ret i32
}
define i32 @test11(i32 %W) {
%X = mul i32 %W, 127
%Y = add i32 %X ,%X
%Z = add i32 %Y, %X
ret i32 %Z
; CHECK: @test11
; CHECK-NEXT: mul i32 %W, 381
; CHECK-NEXT: ret i32
}