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[InstCombine] Optimize binOp(select(),min/max()). #145830

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[InstCombine] Optimize binOp(select(),min/max()). #145830

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73 changes: 73 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
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Expand Up @@ -1349,6 +1349,75 @@ Value *InstCombinerImpl::SimplifySelectsFeedingBinaryOp(BinaryOperator &I,
return nullptr;
};

// Given:
// (Cond ? TVal : FVal) op (MinMaxCand) [SelectIsLHS == true]
// or
// (MinMaxCand) op (Cond ? TVal : FVal) [SelectIsLHS == false]
//
// If MinMaxCand can be expressed as a select with the same Cond,
// then try to optimize it the same way as if it was a select.
// Such patterns may appear after foldSelectInstWithICmpConst().
auto foldWithMinMax = [&](Value *Cond, Value *TVal, Value *FVal,
Value *MinMaxCand,
bool SelectIsLHS = true) -> Value * {
if (True && False)
return nullptr;

const APInt *Cst;
Value *V;
bool FoundMatch = false;

// umax(V, UMIN+1) is equivalent to (V == UMIN) ? UMIN+1 : V
FoundMatch = match(MinMaxCand, m_UMax(m_Value(V), m_APInt(Cst))) &&
!Cst->isMinValue() && (*Cst - 1).isMinValue() &&
match(Cond, m_c_SpecificICmp(ICmpInst::ICMP_EQ, m_Specific(V),
m_SpecificInt(*Cst - 1)));

// umin(V, UMAX-1) is equivalent to (V == UMAX) ? UMAX-1 : V
if (!FoundMatch)
FoundMatch =
match(MinMaxCand, m_UMin(m_Value(V), m_APInt(Cst))) &&
!Cst->isMaxValue() && (*Cst + 1).isMaxValue() &&
match(Cond, m_c_SpecificICmp(ICmpInst::ICMP_EQ, m_Specific(V),
m_SpecificInt(*Cst + 1)));

// smax(V, SMIN+1) is equivalent to (V == SMIN) ? SMIN+1 : V
if (!FoundMatch)
FoundMatch =
match(MinMaxCand, m_SMax(m_Value(V), m_APInt(Cst))) &&
!Cst->isMinSignedValue() && (*Cst - 1).isMinSignedValue() &&
match(Cond, m_c_SpecificICmp(ICmpInst::ICMP_EQ, m_Specific(V),
m_SpecificInt(*Cst - 1)));

// smin(V, SMAX-1) is equivalent to (V == SMAX) ? SMAX-1 : V
if (!FoundMatch)
FoundMatch =
match(MinMaxCand, m_SMin(m_Value(V), m_APInt(Cst))) &&
!Cst->isMaxSignedValue() && (*Cst + 1).isMaxSignedValue() &&
match(Cond, m_c_SpecificICmp(ICmpInst::ICMP_EQ, m_Specific(V),
m_SpecificInt(*Cst + 1)));

if (!FoundMatch)
return nullptr;

Value *OtherTVal = ConstantInt::get(V->getType(), *Cst);
Value *OtherFVal = V;
if (SelectIsLHS) {
True = simplifyBinOp(Opcode, TVal, OtherTVal, FMF, Q);
False = simplifyBinOp(Opcode, FVal, OtherFVal, FMF, Q);
} else {
True = simplifyBinOp(Opcode, OtherTVal, TVal, FMF, Q);
False = simplifyBinOp(Opcode, OtherFVal, FVal, FMF, Q);
}

if (!True || !False)
return nullptr;

Value *SI = Builder.CreateSelect(Cond, True, False);
SI->takeName(&I);
return SI;
};

if (LHSIsSelect && RHSIsSelect && A == D) {
// (A ? B : C) op (A ? E : F) -> A ? (B op E) : (C op F)
Cond = A;
Expand All @@ -1368,13 +1437,17 @@ Value *InstCombinerImpl::SimplifySelectsFeedingBinaryOp(BinaryOperator &I,
False = simplifyBinOp(Opcode, C, RHS, FMF, Q);
if (Value *NewSel = foldAddNegate(B, C, RHS))
return NewSel;
if (Value *NewSel = foldWithMinMax(Cond, B, C, RHS))
return NewSel;
} else if (RHSIsSelect && RHS->hasOneUse()) {
// X op (D ? E : F) -> D ? (X op E) : (X op F)
Cond = D;
True = simplifyBinOp(Opcode, LHS, E, FMF, Q);
False = simplifyBinOp(Opcode, LHS, F, FMF, Q);
if (Value *NewSel = foldAddNegate(E, F, LHS))
return NewSel;
if (Value *NewSel = foldWithMinMax(Cond, E, F, LHS, /*SelectIsLHS=*/false))
return NewSel;
}

if (!True || !False)
Expand Down
107 changes: 107 additions & 0 deletions llvm/test/Transforms/InstCombine/select_arithmetic_with_min_max.ll
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@@ -0,0 +1,107 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes=instcombine -S | FileCheck %s

; These tests check folding of a select and min/max feeding
; the same binary operation. When min/max can be expressed
; as a select with the same condition as in another select,
; the binary op might be applied to the operands of the selects.

define void @test_umax1(i32 %V, ptr %m1, ptr %m2) {
; CHECK-LABEL: @test_umax1(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[V:%.*]], 0
; CHECK-NEXT: [[UMAX:%.*]] = call i32 @llvm.umax.i32(i32 [[V]], i32 1)
; CHECK-NEXT: [[OP:%.*]] = select i1 [[CMP]], i32 8, i32 0
; CHECK-NEXT: store i32 [[UMAX]], ptr [[M1:%.*]], align 4
; CHECK-NEXT: store i32 [[OP]], ptr [[M2:%.*]], align 4
; CHECK-NEXT: ret void
;
%cmp = icmp eq i32 %V, 0
; %umax = select i1 %cmp, i32 1, i32 %V
%umax = call i32 @llvm.umax.i32(i32 %V, i32 1)
%select = select i1 %cmp, i32 9, i32 %V
%op = sub i32 %select, %umax
store i32 %umax, ptr %m1
store i32 %op, ptr %m2
ret void
}

define void @test_umax2(i32 %V, ptr %m1, ptr %m2) {
; CHECK-LABEL: @test_umax2(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[V:%.*]], 0
; CHECK-NEXT: [[UMAX:%.*]] = call i32 @llvm.umax.i32(i32 [[V]], i32 1)
; CHECK-NEXT: [[OP:%.*]] = select i1 [[CMP]], i32 8, i32 0
; CHECK-NEXT: store i32 [[UMAX]], ptr [[M1:%.*]], align 4
; CHECK-NEXT: store i32 [[OP]], ptr [[M2:%.*]], align 4
; CHECK-NEXT: ret void
;
%cmp = icmp eq i32 0, %V
; %umax = select i1 %cmp, i32 1, i32 %V
%umax = call i32 @llvm.umax.i32(i32 1, i32 %V)
%select = select i1 %cmp, i32 9, i32 %V
%op = sub i32 %select, %umax
store i32 %umax, ptr %m1
store i32 %op, ptr %m2
ret void
}

define void @test_umin(i16 %V, ptr %m1, ptr %m2) {
; CHECK-LABEL: @test_umin(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i16 [[V:%.*]], -1
; CHECK-NEXT: [[UMIN:%.*]] = call i16 @llvm.umin.i16(i16 [[V]], i16 -2)
; CHECK-NEXT: [[OP:%.*]] = select i1 [[CMP]], i16 4, i16 0
; CHECK-NEXT: store i16 [[UMIN]], ptr [[M1:%.*]], align 2
; CHECK-NEXT: store i16 [[OP]], ptr [[M2:%.*]], align 2
; CHECK-NEXT: ret void
;
%cmp = icmp eq i16 %V, 65535
; %umin = select i1 %cmp, i16 65534, i16 %V
%umin = call i16 @llvm.umin.i16(i16 %V, i16 65534)
%select = select i1 %cmp, i16 65530, i16 %V
%op = sub i16 %umin, %select
store i16 %umin, ptr %m1
store i16 %op, ptr %m2
ret void
}

define void @test_smax(i8 %V, ptr %m1, ptr %m2) {
; CHECK-LABEL: @test_smax(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[V:%.*]], -128
; CHECK-NEXT: [[SMAX:%.*]] = call i8 @llvm.smax.i8(i8 [[V]], i8 -127)
; CHECK-NEXT: [[OP:%.*]] = select i1 [[CMP]], i8 -128, i8 0
; CHECK-NEXT: store i8 [[SMAX]], ptr [[M1:%.*]], align 1
; CHECK-NEXT: store i8 [[OP]], ptr [[M2:%.*]], align 1
; CHECK-NEXT: ret void
;
%cmp = icmp eq i8 %V, -128
; %smax = select i1 %cmp, i8 -127, i8 %V
%smax = call i8 @llvm.smax.i8(i8 -127, i8 %V)
%select = select i1 %cmp, i8 1, i8 %V
%op = sub i8 %smax, %select
store i8 %smax, ptr %m1
store i8 %op, ptr %m2
ret void
}

define void @test_smin(i8 %V, ptr %m1, ptr %m2) {
; CHECK-LABEL: @test_smin(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[V:%.*]], 127
; CHECK-NEXT: [[SMIN:%.*]] = call i8 @llvm.smin.i8(i8 [[V]], i8 126)
; CHECK-NEXT: [[OP:%.*]] = select i1 [[CMP]], i8 6, i8 0
; CHECK-NEXT: store i8 [[SMIN]], ptr [[M1:%.*]], align 1
; CHECK-NEXT: store i8 [[OP]], ptr [[M2:%.*]], align 1
; CHECK-NEXT: ret void
;
%cmp = icmp eq i8 %V, 127
; %smin = select i1 %cmp, i8 126, i8 %V
%smin = call i8 @llvm.smin.i8(i8 %V, i8 126)
%select = select i1 %cmp, i8 120, i8 %V
%op = sub i8 %smin, %select
store i8 %smin, ptr %m1
store i8 %op, ptr %m2
ret void
}

declare i32 @llvm.umax.i32(i32, i32)
declare i16 @llvm.umin.i16(i16, i16)
declare i8 @llvm.smax.i8(i8, i8)
declare i8 @llvm.smin.i8(i8, i8)