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[InstCombine] Add example usage for new Checked matcher API
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There is no real motivation for this change other than to highlight a
case where the new `Checked` matcher API can handle non-splat-vecs
without increasing code complexity.

Closes #85676
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@goldsteinn
goldsteinn committed May 3, 2024
1 parent 1708788 commit f561daf
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Showing 2 changed files with 12 additions and 20 deletions.
16 changes: 6 additions & 10 deletions llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7128,34 +7128,30 @@ Instruction *InstCombinerImpl::foldICmpCommutative(ICmpInst::Predicate Pred,
return replaceInstUsesWith(CxtI, V);

// Folding (X / Y) pred X => X swap(pred) 0 for constant Y other than 0 or 1
auto CheckUGT1 = [](const APInt &Divisor) { return Divisor.ugt(1); };
{
const APInt *Divisor;
if (match(Op0, m_UDiv(m_Specific(Op1), m_APInt(Divisor))) &&
Divisor->ugt(1)) {
if (match(Op0, m_UDiv(m_Specific(Op1), m_CheckedInt(CheckUGT1)))) {
return new ICmpInst(ICmpInst::getSwappedPredicate(Pred), Op1,
Constant::getNullValue(Op1->getType()));
}

if (!ICmpInst::isUnsigned(Pred) &&
match(Op0, m_SDiv(m_Specific(Op1), m_APInt(Divisor))) &&
Divisor->ugt(1)) {
match(Op0, m_SDiv(m_Specific(Op1), m_CheckedInt(CheckUGT1)))) {
return new ICmpInst(ICmpInst::getSwappedPredicate(Pred), Op1,
Constant::getNullValue(Op1->getType()));
}
}

// Another case of this fold is (X >> Y) pred X => X swap(pred) 0 if Y != 0
auto CheckNE0 = [](const APInt &Shift) { return !Shift.isZero(); };
{
const APInt *Shift;
if (match(Op0, m_LShr(m_Specific(Op1), m_APInt(Shift))) &&
!Shift->isZero()) {
if (match(Op0, m_LShr(m_Specific(Op1), m_CheckedInt(CheckNE0)))) {
return new ICmpInst(ICmpInst::getSwappedPredicate(Pred), Op1,
Constant::getNullValue(Op1->getType()));
}

if ((Pred == CmpInst::ICMP_SLT || Pred == CmpInst::ICMP_SGE) &&
match(Op0, m_AShr(m_Specific(Op1), m_APInt(Shift))) &&
!Shift->isZero()) {
match(Op0, m_AShr(m_Specific(Op1), m_CheckedInt(CheckNE0)))) {
return new ICmpInst(ICmpInst::getSwappedPredicate(Pred), Op1,
Constant::getNullValue(Op1->getType()));
}
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16 changes: 6 additions & 10 deletions llvm/test/Transforms/InstCombine/icmp-div-constant.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -401,9 +401,8 @@ define i1 @udiv_x_by_const_cmp_x(i32 %x) {

define <2 x i1> @udiv_x_by_const_cmp_x_non_splat(<2 x i32> %x) {
; CHECK-LABEL: @udiv_x_by_const_cmp_x_non_splat(
; CHECK-NEXT: [[TMP1:%.*]] = udiv <2 x i32> [[X:%.*]], <i32 123, i32 -123>
; CHECK-NEXT: [[TMP2:%.*]] = icmp slt <2 x i32> [[TMP1]], [[X]]
; CHECK-NEXT: ret <2 x i1> [[TMP2]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt <2 x i32> [[X:%.*]], zeroinitializer
; CHECK-NEXT: ret <2 x i1> [[TMP1]]
;
%1 = udiv <2 x i32> %x, <i32 123, i32 -123>
%2 = icmp slt <2 x i32> %1, %x
Expand All @@ -413,9 +412,8 @@ define <2 x i1> @udiv_x_by_const_cmp_x_non_splat(<2 x i32> %x) {

define <2 x i1> @sdiv_x_by_const_cmp_x_non_splat(<2 x i32> %x) {
; CHECK-LABEL: @sdiv_x_by_const_cmp_x_non_splat(
; CHECK-NEXT: [[TMP1:%.*]] = sdiv <2 x i32> [[X:%.*]], <i32 2, i32 3>
; CHECK-NEXT: [[TMP2:%.*]] = icmp eq <2 x i32> [[TMP1]], [[X]]
; CHECK-NEXT: ret <2 x i1> [[TMP2]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp eq <2 x i32> [[X:%.*]], zeroinitializer
; CHECK-NEXT: ret <2 x i1> [[TMP1]]
;
%1 = sdiv <2 x i32> %x, <i32 2, i32 3>
%2 = icmp eq <2 x i32> %1, %x
Expand Down Expand Up @@ -446,8 +444,7 @@ define <4 x i1> @lshr_by_const_cmp_sle_value(<4 x i32> %x) {

define <4 x i1> @lshr_by_const_cmp_sle_value_non_splat(<4 x i32> %x) {
; CHECK-LABEL: @lshr_by_const_cmp_sle_value_non_splat(
; CHECK-NEXT: [[V:%.*]] = lshr <4 x i32> [[X:%.*]], <i32 3, i32 3, i32 3, i32 5>
; CHECK-NEXT: [[R:%.*]] = icmp sle <4 x i32> [[V]], [[X]]
; CHECK-NEXT: [[R:%.*]] = icmp sgt <4 x i32> [[X:%.*]], <i32 -1, i32 -1, i32 -1, i32 -1>
; CHECK-NEXT: ret <4 x i1> [[R]]
;
%v = lshr <4 x i32> %x, <i32 3, i32 3, i32 3, i32 5>
Expand All @@ -458,8 +455,7 @@ define <4 x i1> @lshr_by_const_cmp_sle_value_non_splat(<4 x i32> %x) {

define <4 x i1> @ashr_by_const_cmp_sge_value_non_splat(<4 x i32> %x) {
; CHECK-LABEL: @ashr_by_const_cmp_sge_value_non_splat(
; CHECK-NEXT: [[V:%.*]] = ashr <4 x i32> [[X:%.*]], <i32 1, i32 2, i32 3, i32 4>
; CHECK-NEXT: [[R:%.*]] = icmp sge <4 x i32> [[V]], [[X]]
; CHECK-NEXT: [[R:%.*]] = icmp slt <4 x i32> [[X:%.*]], <i32 1, i32 1, i32 1, i32 1>
; CHECK-NEXT: ret <4 x i1> [[R]]
;
%v = ashr <4 x i32> %x, <i32 1, i32 2, i32 3, i32 4>
Expand Down

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