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[InstCombine] Support logical and in masked icmp fold
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Most of the folds implemented in this function work fine with
logical operations. We only need to be careful for the cases that
work on non-constant masks, where the RHS operand shouldn't be
poison.

This is a conservative implementation that bails out of illegal
transforms, but we could also change these to insert freeze instead.
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@nikic
nikic committed May 24, 2022
1 parent 4aa32e1 commit a7c079a
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Showing 2 changed files with 35 additions and 43 deletions.
23 changes: 14 additions & 9 deletions llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -365,6 +365,7 @@ getMaskedTypeForICmpPair(Value *&A, Value *&B, Value *&C,
/// (icmp(A & X) ==/!= Y), where the left-hand side is of type Mask_NotAllZeros
/// and the right hand side is of type BMask_Mixed. For example,
/// (icmp (A & 12) != 0) & (icmp (A & 15) == 8) -> (icmp (A & 15) == 8).
/// Also used for logical and/or, must be poison safe.
static Value *foldLogOpOfMaskedICmps_NotAllZeros_BMask_Mixed(
ICmpInst *LHS, ICmpInst *RHS, bool IsAnd, Value *A, Value *B, Value *C,
Value *D, Value *E, ICmpInst::Predicate PredL, ICmpInst::Predicate PredR,
Expand Down Expand Up @@ -486,6 +487,7 @@ static Value *foldLogOpOfMaskedICmps_NotAllZeros_BMask_Mixed(
/// Try to fold (icmp(A & B) ==/!= 0) &/| (icmp(A & D) ==/!= E) into a single
/// (icmp(A & X) ==/!= Y), where the left-hand side and the right hand side
/// aren't of the common mask pattern type.
/// Also used for logical and/or, must be poison safe.
static Value *foldLogOpOfMaskedICmpsAsymmetric(
ICmpInst *LHS, ICmpInst *RHS, bool IsAnd, Value *A, Value *B, Value *C,
Value *D, Value *E, ICmpInst::Predicate PredL, ICmpInst::Predicate PredR,
Expand Down Expand Up @@ -520,6 +522,7 @@ static Value *foldLogOpOfMaskedICmpsAsymmetric(
/// Try to fold (icmp(A & B) ==/!= C) &/| (icmp(A & D) ==/!= E)
/// into a single (icmp(A & X) ==/!= Y).
static Value *foldLogOpOfMaskedICmps(ICmpInst *LHS, ICmpInst *RHS, bool IsAnd,
bool IsLogical,
InstCombiner::BuilderTy &Builder) {
Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr, *E = nullptr;
ICmpInst::Predicate PredL = LHS->getPredicate(), PredR = RHS->getPredicate();
Expand Down Expand Up @@ -564,6 +567,8 @@ static Value *foldLogOpOfMaskedICmps(ICmpInst *LHS, ICmpInst *RHS, bool IsAnd,
if (Mask & Mask_AllZeros) {
// (icmp eq (A & B), 0) & (icmp eq (A & D), 0)
// -> (icmp eq (A & (B|D)), 0)
if (IsLogical && !isGuaranteedNotToBeUndefOrPoison(D))
return nullptr; // TODO: Use freeze?
Value *NewOr = Builder.CreateOr(B, D);
Value *NewAnd = Builder.CreateAnd(A, NewOr);
// We can't use C as zero because we might actually handle
Expand All @@ -575,13 +580,17 @@ static Value *foldLogOpOfMaskedICmps(ICmpInst *LHS, ICmpInst *RHS, bool IsAnd,
if (Mask & BMask_AllOnes) {
// (icmp eq (A & B), B) & (icmp eq (A & D), D)
// -> (icmp eq (A & (B|D)), (B|D))
if (IsLogical && !isGuaranteedNotToBeUndefOrPoison(D))
return nullptr; // TODO: Use freeze?
Value *NewOr = Builder.CreateOr(B, D);
Value *NewAnd = Builder.CreateAnd(A, NewOr);
return Builder.CreateICmp(NewCC, NewAnd, NewOr);
}
if (Mask & AMask_AllOnes) {
// (icmp eq (A & B), A) & (icmp eq (A & D), A)
// -> (icmp eq (A & (B&D)), A)
if (IsLogical && !isGuaranteedNotToBeUndefOrPoison(D))
return nullptr; // TODO: Use freeze?
Value *NewAnd1 = Builder.CreateAnd(B, D);
Value *NewAnd2 = Builder.CreateAnd(A, NewAnd1);
return Builder.CreateICmp(NewCC, NewAnd2, A);
Expand Down Expand Up @@ -2442,15 +2451,11 @@ Value *InstCombinerImpl::foldAndOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
}
}

// TODO: Some (but not all) of the patterns handled by this function are
// safe with logical and/or.
if (!IsLogical) {
// handle (roughly):
// (icmp ne (A & B), C) | (icmp ne (A & D), E)
// (icmp eq (A & B), C) & (icmp eq (A & D), E)
if (Value *V = foldLogOpOfMaskedICmps(LHS, RHS, IsAnd, Builder))
return V;
}
// handle (roughly):
// (icmp ne (A & B), C) | (icmp ne (A & D), E)
// (icmp eq (A & B), C) & (icmp eq (A & D), E)
if (Value *V = foldLogOpOfMaskedICmps(LHS, RHS, IsAnd, IsLogical, Builder))
return V;

// TODO: One of these directions is fine with logical and/or, the other could
// be supported by inserting freeze.
Expand Down
55 changes: 21 additions & 34 deletions llvm/test/Transforms/InstCombine/and-or-icmps.ll
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1981,13 +1981,10 @@ define i1 @logical_or_logical_or_icmps_comm3(i8 %x, i8 %y, i8 %z) {

define i1 @bitwise_and_logical_and_masked_icmp_asymmetric(i1 %c, i32 %x) {
; CHECK-LABEL: @bitwise_and_logical_and_masked_icmp_asymmetric(
; CHECK-NEXT: [[X_M1:%.*]] = and i32 [[X:%.*]], 255
; CHECK-NEXT: [[C1:%.*]] = icmp ne i32 [[X_M1]], 0
; CHECK-NEXT: [[AND1:%.*]] = select i1 [[C1]], i1 [[C:%.*]], i1 false
; CHECK-NEXT: [[X_M2:%.*]] = and i32 [[X]], 11
; CHECK-NEXT: [[X_M2:%.*]] = and i32 [[X:%.*]], 11
; CHECK-NEXT: [[C2:%.*]] = icmp eq i32 [[X_M2]], 11
; CHECK-NEXT: [[AND2:%.*]] = and i1 [[AND1]], [[C2]]
; CHECK-NEXT: ret i1 [[AND2]]
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[C2]], i1 [[C:%.*]], i1 false
; CHECK-NEXT: ret i1 [[TMP1]]
;
%x.m1 = and i32 %x, 255
%c1 = icmp ne i32 %x.m1, 0
Expand All @@ -2000,13 +1997,10 @@ define i1 @bitwise_and_logical_and_masked_icmp_asymmetric(i1 %c, i32 %x) {

define i1 @bitwise_and_logical_and_masked_icmp_allzeros(i1 %c, i32 %x) {
; CHECK-LABEL: @bitwise_and_logical_and_masked_icmp_allzeros(
; CHECK-NEXT: [[X_M1:%.*]] = and i32 [[X:%.*]], 8
; CHECK-NEXT: [[C1:%.*]] = icmp eq i32 [[X_M1]], 0
; CHECK-NEXT: [[AND1:%.*]] = select i1 [[C1]], i1 [[C:%.*]], i1 false
; CHECK-NEXT: [[X_M2:%.*]] = and i32 [[X]], 7
; CHECK-NEXT: [[C2:%.*]] = icmp eq i32 [[X_M2]], 0
; CHECK-NEXT: [[AND2:%.*]] = and i1 [[AND1]], [[C2]]
; CHECK-NEXT: ret i1 [[AND2]]
; CHECK-NEXT: [[TMP1:%.*]] = and i32 [[X:%.*]], 15
; CHECK-NEXT: [[TMP2:%.*]] = icmp eq i32 [[TMP1]], 0
; CHECK-NEXT: [[TMP3:%.*]] = select i1 [[TMP2]], i1 [[C:%.*]], i1 false
; CHECK-NEXT: ret i1 [[TMP3]]
;
%x.m1 = and i32 %x, 8
%c1 = icmp eq i32 %x.m1, 0
Expand All @@ -2019,13 +2013,11 @@ define i1 @bitwise_and_logical_and_masked_icmp_allzeros(i1 %c, i32 %x) {

define i1 @bitwise_and_logical_and_masked_icmp_allzeros_poison1(i1 %c, i32 %x, i32 %y) {
; CHECK-LABEL: @bitwise_and_logical_and_masked_icmp_allzeros_poison1(
; CHECK-NEXT: [[X_M1:%.*]] = and i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[C1:%.*]] = icmp eq i32 [[X_M1]], 0
; CHECK-NEXT: [[AND1:%.*]] = select i1 [[C1]], i1 [[C:%.*]], i1 false
; CHECK-NEXT: [[X_M2:%.*]] = and i32 [[X]], 7
; CHECK-NEXT: [[C2:%.*]] = icmp eq i32 [[X_M2]], 0
; CHECK-NEXT: [[AND2:%.*]] = and i1 [[AND1]], [[C2]]
; CHECK-NEXT: ret i1 [[AND2]]
; CHECK-NEXT: [[TMP1:%.*]] = or i32 [[Y:%.*]], 7
; CHECK-NEXT: [[TMP2:%.*]] = and i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i32 [[TMP2]], 0
; CHECK-NEXT: [[TMP4:%.*]] = select i1 [[TMP3]], i1 [[C:%.*]], i1 false
; CHECK-NEXT: ret i1 [[TMP4]]
;
%x.m1 = and i32 %x, %y
%c1 = icmp eq i32 %x.m1, 0
Expand Down Expand Up @@ -2057,13 +2049,10 @@ define i1 @bitwise_and_logical_and_masked_icmp_allzeros_poison2(i1 %c, i32 %x, i

define i1 @bitwise_and_logical_and_masked_icmp_allones(i1 %c, i32 %x) {
; CHECK-LABEL: @bitwise_and_logical_and_masked_icmp_allones(
; CHECK-NEXT: [[X_M1:%.*]] = and i32 [[X:%.*]], 8
; CHECK-NEXT: [[C1:%.*]] = icmp ne i32 [[X_M1]], 0
; CHECK-NEXT: [[AND1:%.*]] = select i1 [[C1]], i1 [[C:%.*]], i1 false
; CHECK-NEXT: [[X_M2:%.*]] = and i32 [[X]], 7
; CHECK-NEXT: [[C2:%.*]] = icmp eq i32 [[X_M2]], 7
; CHECK-NEXT: [[AND2:%.*]] = and i1 [[AND1]], [[C2]]
; CHECK-NEXT: ret i1 [[AND2]]
; CHECK-NEXT: [[TMP1:%.*]] = and i32 [[X:%.*]], 15
; CHECK-NEXT: [[TMP2:%.*]] = icmp eq i32 [[TMP1]], 15
; CHECK-NEXT: [[TMP3:%.*]] = select i1 [[TMP2]], i1 [[C:%.*]], i1 false
; CHECK-NEXT: ret i1 [[TMP3]]
;
%x.m1 = and i32 %x, 8
%c1 = icmp eq i32 %x.m1, 8
Expand All @@ -2076,13 +2065,11 @@ define i1 @bitwise_and_logical_and_masked_icmp_allones(i1 %c, i32 %x) {

define i1 @bitwise_and_logical_and_masked_icmp_allones_poison1(i1 %c, i32 %x, i32 %y) {
; CHECK-LABEL: @bitwise_and_logical_and_masked_icmp_allones_poison1(
; CHECK-NEXT: [[X_M1:%.*]] = and i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[C1:%.*]] = icmp eq i32 [[X_M1]], [[Y]]
; CHECK-NEXT: [[AND1:%.*]] = select i1 [[C1]], i1 [[C:%.*]], i1 false
; CHECK-NEXT: [[X_M2:%.*]] = and i32 [[X]], 7
; CHECK-NEXT: [[C2:%.*]] = icmp eq i32 [[X_M2]], 7
; CHECK-NEXT: [[AND2:%.*]] = and i1 [[AND1]], [[C2]]
; CHECK-NEXT: ret i1 [[AND2]]
; CHECK-NEXT: [[TMP1:%.*]] = or i32 [[Y:%.*]], 7
; CHECK-NEXT: [[TMP2:%.*]] = and i32 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i32 [[TMP2]], [[TMP1]]
; CHECK-NEXT: [[TMP4:%.*]] = select i1 [[TMP3]], i1 [[C:%.*]], i1 false
; CHECK-NEXT: ret i1 [[TMP4]]
;
%x.m1 = and i32 %x, %y
%c1 = icmp eq i32 %x.m1, %y
Expand Down

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