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LICM: hoist BO assoc when BinOp is in RHS #107072

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merged 3 commits into from
Sep 4, 2024
Merged

LICM: hoist BO assoc when BinOp is in RHS #107072

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2bc99bf
LICM: hoist BO assoc when BinOp is in RHS
artagnon Sep 3, 2024
8e8f1d7
LICM: generalize further strengthening check
artagnon Sep 4, 2024
e575d84
LICM: handle BinOp in RHS correctly
artagnon Sep 4, 2024
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37 changes: 25 additions & 12 deletions llvm/lib/Transforms/Scalar/LICM.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2805,13 +2805,11 @@ static bool hoistMulAddAssociation(Instruction &I, Loop &L,
///
/// 1. "(LV op C1) op C2" ==> "LV op (C1 op C2)" if op is an associative BinOp
/// 2. "(C1 op LV) op C2" ==> "LV op (C1 op C2)" if op is a commutative BinOp
/// 3. "C2 op (C1 op LV)" ==> "(C2 op C1) op LV" if op an associative BinOp
/// 4. "C2 op (LV op C1)" ==> "(C2 op C1) op LV" if op is a commutative BinOp
///
/// where LV is a loop variant, and C1 and C2 are loop invariants that we want
/// to hoist.
///
/// TODO: This can be extended to more cases such as
/// 1. "C1 op (C2 op LV)" ==> "(C1 op C2) op LV" if op an associative BinOp
/// 2. "C1 op (LV op C2)" ==> "(C1 op C2) op LV" if op is a commutative BinOp
static bool hoistBOAssociation(Instruction &I, Loop &L,
ICFLoopSafetyInfo &SafetyInfo,
MemorySSAUpdater &MSSAU, AssumptionCache *AC,
Expand All @@ -2825,30 +2823,45 @@ static bool hoistBOAssociation(Instruction &I, Loop &L,
if (Opcode != Instruction::Add && Opcode != Instruction::Mul)
return false;

auto *BO0 = dyn_cast<BinaryOperator>(BO->getOperand(0));
bool BinOpInRHS = isa<BinaryOperator>(BO->getOperand(1));
auto *BO0 = dyn_cast<BinaryOperator>(BO->getOperand(BinOpInRHS));
if (!BO0 || BO0->getOpcode() != Opcode || !BO0->isAssociative() ||
BO0->hasNUsesOrMore(3))
return false;

Value *LV = BO0->getOperand(0);
Value *C1 = BO0->getOperand(1);
Value *C2 = BO->getOperand(1);
Value *C2 = BO->getOperand(!BinOpInRHS);

if (L.isLoopInvariant(LV) && !L.isLoopInvariant(C1)) {
assert(BO0->isCommutative() && "Associativity implies commutativity");
if (!L.isLoopInvariant(C2))
return false;
if (!L.isLoopInvariant(LV) && L.isLoopInvariant(C1)) {
if (BinOpInRHS)
assert(BO0->isCommutative() && "Associativity implies commutativity");
} else if (L.isLoopInvariant(LV) && !L.isLoopInvariant(C1)) {
if (!BinOpInRHS)
assert(BO0->isCommutative() && "Associativity implies commutativity");
std::swap(LV, C1);
}
if (L.isLoopInvariant(LV) || !L.isLoopInvariant(C1) || !L.isLoopInvariant(C2))
} else {
return false;
}

auto *Preheader = L.getLoopPreheader();
assert(Preheader && "Loop is not in simplify form?");

// To create C2 op C1, instead of C1 op C2.
if (BinOpInRHS)
std::swap(C1, C2);

IRBuilder<> Builder(Preheader->getTerminator());
auto *Inv = Builder.CreateBinOp(Opcode, C1, C2, "invariant.op");

auto *NewBO = BinaryOperator::Create(
Opcode, LV, Inv, BO->getName() + ".reass", BO->getIterator());
auto *NewBO =
BinOpInRHS
? BinaryOperator::Create(Opcode, Inv, LV, BO->getName() + ".reass",
BO->getIterator())
: BinaryOperator::Create(Opcode, LV, Inv, BO->getName() + ".reass",
BO->getIterator());

// Copy NUW for ADDs if both instructions have it.
if (Opcode == Instruction::Add && BO->hasNoUnsignedWrap() &&
Expand Down
107 changes: 104 additions & 3 deletions llvm/test/Transforms/LICM/hoist-binop.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -67,8 +67,8 @@ loop:
br label %loop
}


; Hoist ADD and copy NUW if both ops have it. Commutative version.
; Hoist ADD and copy NUW if both ops have it.
; Version where operands are commuted.
define void @add_nuw_comm(i64 %c1, i64 %c2) {
; CHECK-LABEL: @add_nuw_comm(
; CHECK-NEXT: entry:
Expand All @@ -92,6 +92,56 @@ loop:
br label %loop
}

; Hoist ADD and copy NUW if both ops have it.
; Another version where operands are commuted.
define void @add_nuw_comm2(i64 %c1, i64 %c2) {
; CHECK-LABEL: @add_nuw_comm2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[INVARIANT_OP:%.*]] = add nuw i64 [[C2:%.*]], [[C1:%.*]]
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[INDEX_NEXT_REASS:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[STEP_ADD:%.*]] = add nuw i64 [[INDEX]], [[C1]]
; CHECK-NEXT: call void @use(i64 [[STEP_ADD]])
; CHECK-NEXT: [[INDEX_NEXT_REASS]] = add nuw i64 [[INVARIANT_OP]], [[INDEX]]
; CHECK-NEXT: br label [[LOOP]]
;
entry:
br label %loop

loop:
%index = phi i64 [ 0, %entry ], [ %index.next, %loop ]
%step.add = add nuw i64 %index, %c1
call void @use(i64 %step.add)
%index.next = add nuw i64 %c2, %step.add
br label %loop
}

; Hoist ADD and copy NUW if both ops have it.
; Another version where operands are commuted.
define void @add_nuw_comm3(i64 %c1, i64 %c2) {
; CHECK-LABEL: @add_nuw_comm3(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[INVARIANT_OP:%.*]] = add nuw i64 [[C2:%.*]], [[C1:%.*]]
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[INDEX_NEXT_REASS:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[STEP_ADD:%.*]] = add nuw i64 [[C1]], [[INDEX]]
; CHECK-NEXT: call void @use(i64 [[STEP_ADD]])
; CHECK-NEXT: [[INDEX_NEXT_REASS]] = add nuw i64 [[INVARIANT_OP]], [[INDEX]]
; CHECK-NEXT: br label [[LOOP]]
;
entry:
br label %loop

loop:
%index = phi i64 [ 0, %entry ], [ %index.next, %loop ]
%step.add = add nuw i64 %c1, %index
call void @use(i64 %step.add)
%index.next = add nuw i64 %c2, %step.add
br label %loop
}

; Hoist MUL and drop NUW even if both ops have it.
define void @mul_nuw(i64 %c1, i64 %c2) {
; CHECK-LABEL: @mul_nuw(
Expand All @@ -116,7 +166,8 @@ loop:
br label %loop
}

; Hoist MUL and drop NUW even if both ops have it. Commutative version.
; Hoist MUL and drop NUW even if both ops have it.
; Version where operands are commuted.
define void @mul_nuw_comm(i64 %c1, i64 %c2) {
; CHECK-LABEL: @mul_nuw_comm(
; CHECK-NEXT: entry:
Expand All @@ -140,6 +191,56 @@ loop:
br label %loop
}

; Hoist MUL and drop NUW even if both ops have it.
; Another version where operands are commuted.
define void @mul_nuw_comm2(i64 %c1, i64 %c2) {
; CHECK-LABEL: @mul_nuw_comm2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[INVARIANT_OP:%.*]] = mul i64 [[C2:%.*]], [[C1:%.*]]
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[INDEX_NEXT_REASS:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[STEP_ADD:%.*]] = mul nuw i64 [[INDEX]], [[C1]]
; CHECK-NEXT: call void @use(i64 [[STEP_ADD]])
; CHECK-NEXT: [[INDEX_NEXT_REASS]] = mul i64 [[INVARIANT_OP]], [[INDEX]]
; CHECK-NEXT: br label [[LOOP]]
;
entry:
br label %loop

loop:
%index = phi i64 [ 0, %entry ], [ %index.next, %loop ]
%step.add = mul nuw i64 %index, %c1
call void @use(i64 %step.add)
%index.next = mul nuw i64 %c2, %step.add
br label %loop
}

; Hoist MUL and drop NUW even if both ops have it.
; Another version where operands are commuted.
define void @mul_nuw_comm3(i64 %c1, i64 %c2) {
; CHECK-LABEL: @mul_nuw_comm3(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[INVARIANT_OP:%.*]] = mul i64 [[C2:%.*]], [[C1:%.*]]
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[INDEX_NEXT_REASS:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[STEP_ADD:%.*]] = mul nuw i64 [[C1]], [[INDEX]]
; CHECK-NEXT: call void @use(i64 [[STEP_ADD]])
; CHECK-NEXT: [[INDEX_NEXT_REASS]] = mul i64 [[INVARIANT_OP]], [[INDEX]]
; CHECK-NEXT: br label [[LOOP]]
;
entry:
br label %loop

loop:
%index = phi i64 [ 0, %entry ], [ %index.next, %loop ]
%step.add = mul nuw i64 %c1, %index
call void @use(i64 %step.add)
%index.next = mul nuw i64 %c2, %step.add
br label %loop
}

; Hoist ADD but don't copy NUW if only one op has it.
define void @add_no_nuw(i64 %c1, i64 %c2) {
; CHECK-LABEL: @add_no_nuw(
Expand Down
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