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[InstCombine] Fold (icmp eq/ne (or (select cond, 0/NZ, 0/NZ), X), 0)
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Four cases:
`(icmp eq (or (select cond, 0, NonZero), Other))`
 -> `(and cond, (icmp eq Other, 0))`
`(icmp ne (or (select cond, NonZero, 0), Other))`
 -> `(or cond, (icmp ne Other, 0))`
`(icmp ne (or (select cond, 0, NonZero), Other))`
 -> `(or (not cond), (icmp ne Other, 0))`
`(icmp eq (or (select cond, NonZero, 0), Other))`
 -> `(and (not cond), (icmp eq Other, 0))`

These cases came up in tests on: #88088

Proofs: https://alive2.llvm.org/ce/z/ojGo_J
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@goldsteinn
goldsteinn committed May 5, 2024
1 parent 06a40e4 commit f43e49a
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50 changes: 50 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3483,6 +3483,56 @@ Instruction *InstCombinerImpl::foldICmpBinOpEqualityWithConstant(
Value *And = Builder.CreateAnd(BOp0, NotBOC);
return new ICmpInst(Pred, And, NotBOC);
}
// (icmp eq (or (select cond, 0, NonZero), Other))
// -> (and cond, (icmp eq Other, 0))
// (icmp ne (or (select cond, NonZero, 0), Other))
// -> (or cond, (icmp ne Other, 0))
// (icmp ne (or (select cond, 0, NonZero), Other))
// -> (or (not cond), (icmp ne Other, 0))
// (icmp eq (or (select cond, NonZero, 0), Other))
// -> (and (not cond), (icmp eq Other, 0))
Value *Cond, *TV, *FV, *Other;
if (C.isZero() && BO->hasOneUse() &&
match(BO, m_c_Or(m_Select(m_Value(Cond), m_Value(TV), m_Value(FV)),
m_Value(Other)))) {
const SimplifyQuery Q = SQ.getWithInstruction(&Cmp);
// Easy case is if eq/ne matches whether 0 is trueval/falseval.
if (Pred == ICmpInst::ICMP_EQ
? (match(TV, m_SpecificInt(C)) && isKnownNonZero(FV, Q))
: (match(FV, m_SpecificInt(C)) && isKnownNonZero(TV, Q))) {
Value *Cmp = Builder.CreateICmp(
Pred, Other, Constant::getNullValue(Other->getType()));
return BinaryOperator::Create(
Pred == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or, Cmp,
Cond);
}
// Harder case is if eq/ne matches whether 0 is falseval/trueval. In this
// case we need to invert the select condition so we need to be careful to
// avoid creating extra instructions.
if (Pred == ICmpInst::ICMP_EQ
? (match(FV, m_SpecificInt(C)) && isKnownNonZero(TV, Q))
: (match(TV, m_SpecificInt(C)) && isKnownNonZero(FV, Q))) {
Value *NotCond = nullptr;
// If the select is one use, we are essentially replacing select with
// `(not Cond)`.
if (match(BO, m_c_Or(m_OneUse(m_Select(m_Specific(Cond), m_Specific(TV),
m_Specific(FV))),
m_Value())))
NotCond = Builder.CreateNot(Cond);
// Otherwise, see if we can get NotCond for free.
else
NotCond =
getFreelyInverted(Cond, /*WillInvertAllUses=*/false, &Builder);

if (NotCond) {
Value *Cmp = Builder.CreateICmp(
Pred, Other, Constant::getNullValue(Other->getType()));
return BinaryOperator::Create(
Pred == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or,
Cmp, NotCond);
}
}
}
break;
}
case Instruction::UDiv:
Expand Down
48 changes: 21 additions & 27 deletions llvm/test/Transforms/InstCombine/icmp-or-of-select-with-zero.ll
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5,11 +5,9 @@ declare void @use.i8(i8)
declare void @use.i1(i1)
define i1 @src_tv_eq(i1 %c0, i8 %x, i8 %yy) {
; CHECK-LABEL: @src_tv_eq(
; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[YY:%.*]], 1
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[C0:%.*]], i8 0, i8 [[Y]]
; CHECK-NEXT: [[SELX:%.*]] = or i8 [[SEL]], [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[SELX]], 0
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[SELX:%.*]], 0
; CHECK-NEXT: [[R1:%.*]] = and i1 [[R]], [[C0:%.*]]
; CHECK-NEXT: ret i1 [[R1]]
;
%y = add nuw i8 %yy, 1
%sel = select i1 %c0, i8 0, i8 %y
Expand Down Expand Up @@ -52,11 +50,9 @@ define i1 @src_tv_eq_fail_tv_nonzero(i1 %c0, i8 %x, i8 %yy) {

define i1 @src_fv_ne(i1 %c0, i8 %x, i8 %yy) {
; CHECK-LABEL: @src_fv_ne(
; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[YY:%.*]], 1
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[C0:%.*]], i8 [[Y]], i8 0
; CHECK-NEXT: [[SELX:%.*]] = or i8 [[SEL]], [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[SELX]], 0
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[SELX:%.*]], 0
; CHECK-NEXT: [[R1:%.*]] = or i1 [[R]], [[C0:%.*]]
; CHECK-NEXT: ret i1 [[R1]]
;
%y = add nuw i8 %yy, 1
%sel = select i1 %c0, i8 %y, i8 0
Expand All @@ -82,11 +78,10 @@ define i1 @src_fv_ne_fail_maybe_zero(i1 %c0, i8 %x, i8 %yy) {

define i1 @src_tv_ne(i1 %c0, i8 %x, i8 %yy) {
; CHECK-LABEL: @src_tv_ne(
; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[YY:%.*]], 1
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[C0:%.*]], i8 0, i8 [[Y]]
; CHECK-NEXT: [[SELX:%.*]] = or i8 [[SEL]], [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[SELX]], 0
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: [[TMP1:%.*]] = xor i1 [[C0:%.*]], true
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[SELX:%.*]], 0
; CHECK-NEXT: [[R1:%.*]] = or i1 [[R]], [[TMP1]]
; CHECK-NEXT: ret i1 [[R1]]
;
%y = add nuw i8 %yy, 1
%sel = select i1 %c0, i8 0, i8 %y
Expand All @@ -112,11 +107,10 @@ define i1 @src_tv_ne_fail_cmp_nonzero(i1 %c0, i8 %x, i8 %yy) {

define i1 @src_fv_eq(i1 %c0, i8 %x, i8 %yy) {
; CHECK-LABEL: @src_fv_eq(
; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[YY:%.*]], 1
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[C0:%.*]], i8 [[Y]], i8 0
; CHECK-NEXT: [[SELX:%.*]] = or i8 [[SEL]], [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[SELX]], 0
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: [[TMP1:%.*]] = xor i1 [[C0:%.*]], true
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[SELX:%.*]], 0
; CHECK-NEXT: [[R1:%.*]] = and i1 [[R]], [[TMP1]]
; CHECK-NEXT: ret i1 [[R1]]
;
%y = add nuw i8 %yy, 1
%sel = select i1 %c0, i8 %y, i8 0
Expand Down Expand Up @@ -172,13 +166,13 @@ define i1 @src_fv_eq_invert2(i1 %c1, i8 %a, i8 %b, i8 %x, i8 %yy) {
; CHECK-LABEL: @src_fv_eq_invert2(
; CHECK-NEXT: [[C0:%.*]] = icmp ugt i8 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[YY:%.*]], 1
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[C0]], i8 [[Y]], i8 0
; CHECK-NEXT: [[CC:%.*]] = or i1 [[C0]], [[C1:%.*]]
; CHECK-NEXT: [[SEL_OTHER:%.*]] = select i1 [[CC]], i8 [[Y]], i8 [[B]]
; CHECK-NEXT: [[SELX:%.*]] = or i8 [[SEL]], [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[SELX]], 0
; CHECK-NEXT: [[TMP1:%.*]] = xor i1 [[C0]], true
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[SELX:%.*]], 0
; CHECK-NEXT: [[R1:%.*]] = and i1 [[R]], [[TMP1]]
; CHECK-NEXT: call void @use.i8(i8 [[SEL_OTHER]])
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: ret i1 [[R1]]
;
%c0 = icmp ugt i8 %a, %b
%y = add nuw i8 %yy, 1
Expand Down Expand Up @@ -225,11 +219,11 @@ define i1 @src_tv_ne_invert(i1 %c1, i8 %a, i8 %b, i8 %x, i8 %yy) {
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[NOT_C0]], i8 [[Y]], i8 0
; CHECK-NEXT: [[CC:%.*]] = or i1 [[C0]], [[C1:%.*]]
; CHECK-NEXT: [[SEL_OTHER:%.*]] = select i1 [[CC]], i8 [[Y]], i8 [[B]]
; CHECK-NEXT: [[SELX:%.*]] = or i8 [[SEL]], [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[SELX]], 0
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[SELX:%.*]], 0
; CHECK-NEXT: [[R1:%.*]] = or i1 [[R]], [[NOT_C0]]
; CHECK-NEXT: call void @use.i8(i8 [[SEL]])
; CHECK-NEXT: call void @use.i8(i8 [[SEL_OTHER]])
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: ret i1 [[R1]]
;
%not_c0 = icmp ugt i8 %a, %b
call void @use.i1(i1 %not_c0)
Expand Down

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