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[InstCombine] Add combines for unsigned comparison of absolute value to constant #172021

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[InstCombine] Add combines for unsigned comparison of absolute value to constant #172021

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45 changes: 45 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7602,6 +7602,51 @@ Instruction *InstCombinerImpl::foldICmpCommutative(CmpPredicate Pred,
}
}

// abs(X) u> K --> K >= 0 ? `X + K u> 2 * K` : `false`
// If abs(INT_MIN) is poison:
// abs(X) u< K --> K >= 1 ? `X + (K - 1) u<= 2 * (K - 1)` : K != 0
{
Value *X;
ConstantInt *C, *K;
bool Frozen = false;
if ((match(Op0,
m_Intrinsic<Intrinsic::abs>(m_Value(X), m_ConstantInt(C))) ||
(Frozen = match(Op0, m_Freeze(m_Intrinsic<Intrinsic::abs>(
m_Value(X), m_ConstantInt(C)))))) &&
match(Op1, m_ConstantInt(K))) {
const APInt KValue = K->getValue();

if (Pred == CmpInst::ICMP_UGT) {
if (KValue.isNegative())
return replaceInstUsesWith(CxtI,
ConstantInt::getFalse(CxtI.getType()));

Value *XPlusK = Builder.CreateAdd(X, K);
if (Frozen)
XPlusK = Builder.CreateFreeze(XPlusK);
return replaceInstUsesWith(
CxtI, Builder.CreateICmpUGT(
XPlusK, ConstantInt::get(K->getType(), 2 * KValue)));
}

if (Pred == CmpInst::ICMP_ULT && !C->getValue().isZero()) {
if (KValue.slt(1))
return replaceInstUsesWith(
CxtI, KValue.isZero() ? ConstantInt::getFalse(CxtI.getType())
: ConstantInt::getTrue(CxtI.getType()));

Value *XPlusKDec =
Builder.CreateAdd(X, ConstantInt::get(K->getType(), KValue - 1));
if (Frozen)
XPlusKDec = Builder.CreateFreeze(XPlusKDec);
return replaceInstUsesWith(
CxtI,
Builder.CreateICmpULE(
XPlusKDec, ConstantInt::get(K->getType(), 2 * (KValue - 1))));
}
}
}

const SimplifyQuery Q = SQ.getWithInstruction(&CxtI);
if (Value *V = foldICmpWithLowBitMaskedVal(Pred, Op0, Op1, Q, *this))
return replaceInstUsesWith(CxtI, V);
Expand Down
96 changes: 96 additions & 0 deletions llvm/test/Transforms/InstCombine/abs-intrinsic.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -997,3 +997,99 @@ define i8 @abs_diff_sle_y_x(i8 %x, i8 %y) {
%cond = select i1 %cmp, i8 %sub, i8 %sub1
ret i8 %cond
}

define i1 @abs_cmp_ule_no_poison(i32 %x) {
; CHECK-LABEL: @abs_cmp_ule_no_poison(
; CHECK-NEXT: [[X_ABS:%.*]] = call i32 @llvm.abs.i32(i32 [[X:%.*]], i1 false)
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[X_ABS]], 32
; CHECK-NEXT: ret i1 [[CMP]]
;
%x.abs = call i32 @llvm.abs.i32(i32 %x, i1 0)
%cmp = icmp ule i32 %x.abs, 31
ret i1 %cmp
}

define i1 @abs_cmp_ule_poison(i32 %x) {
; CHECK-LABEL: @abs_cmp_ule_poison(
; CHECK-NEXT: [[X_ABS_FREEZE:%.*]] = freeze i32 [[X:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[X_ABS_FREEZE]], 31
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[TMP1]], 63
; CHECK-NEXT: ret i1 [[CMP]]
;
%x.abs = call i32 @llvm.abs.i32(i32 %x, i1 1)
%x.abs.freeze = freeze i32 %x.abs
%cmp = icmp ule i32 %x.abs.freeze, 31
ret i1 %cmp
}

define i1 @abs_cmp_ult_no_poison(i32 %x) {
; CHECK-LABEL: @abs_cmp_ult_no_poison(
; CHECK-NEXT: [[X_ABS:%.*]] = call i32 @llvm.abs.i32(i32 [[X:%.*]], i1 false)
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[X_ABS]], 32
; CHECK-NEXT: ret i1 [[CMP]]
;
%x.abs = call i32 @llvm.abs.i32(i32 %x, i1 0)
%cmp = icmp ult i32 %x.abs, 32
ret i1 %cmp
}

define i1 @abs_cmp_ult_poison(i32 %x) {
; CHECK-LABEL: @abs_cmp_ult_poison(
; CHECK-NEXT: [[X_FR:%.*]] = freeze i32 [[X:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[X_FR]], 31
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[TMP1]], 63
; CHECK-NEXT: ret i1 [[CMP]]
;
%x.abs = call i32 @llvm.abs.i32(i32 %x, i1 1)
%x.abs.freeze = freeze i32 %x.abs
%cmp = icmp ult i32 %x.abs.freeze, 32
ret i1 %cmp
}

define i1 @abs_cmp_uge_no_poison(i32 %x) {
; CHECK-LABEL: @abs_cmp_uge_no_poison(
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[X:%.*]], -31
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[TMP1]], -61
; CHECK-NEXT: ret i1 [[CMP]]
;
%x.abs = call i32 @llvm.abs.i32(i32 %x, i1 0)
%cmp = icmp ugt i32 %x.abs, 30
ret i1 %cmp
}

define i1 @abs_cmp_uge_poison(i32 %x) {
; CHECK-LABEL: @abs_cmp_uge_poison(
; CHECK-NEXT: [[X_FR:%.*]] = freeze i32 [[X:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[X_FR]], -31
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[TMP1]], -61
; CHECK-NEXT: ret i1 [[CMP]]
;
%x.abs = call i32 @llvm.abs.i32(i32 %x, i1 1)
%x.abs.freeze = freeze i32 %x.abs
%cmp = icmp ugt i32 %x.abs.freeze, 30
ret i1 %cmp
}

define i1 @abs_cmp_ugt_no_poison(i32 %x) {
; CHECK-LABEL: @abs_cmp_ugt_no_poison(
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[X:%.*]], -32
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[TMP1]], -63
; CHECK-NEXT: ret i1 [[CMP]]
;
%x.abs = call i32 @llvm.abs.i32(i32 %x, i1 0)
%cmp = icmp ugt i32 %x.abs, 31
ret i1 %cmp
}

define i1 @abs_cmp_ugt_poison(i32 %x) {
; CHECK-LABEL: @abs_cmp_ugt_poison(
; CHECK-NEXT: [[X:%.*]] = freeze i32 [[X1:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[X]], -32
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[TMP1]], -63
; CHECK-NEXT: ret i1 [[CMP]]
;
%x.abs = call i32 @llvm.abs.i32(i32 %x, i1 1)
%x.abs.freeze = freeze i32 %x.abs
%cmp = icmp ugt i32 %x.abs.freeze, 31
ret i1 %cmp
}