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[InstCombine] fold (a == c && b != c) || (a != c && b == c)) to (a == c) == (b != c) #94915

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Merged
merged 8 commits into from
Jun 23, 2024
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[InstCombine] fold (a == c && b != c) || (a != c && b == c)) to (a == c) == (b != c) #94915

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3ec3b32
[InstCombine] fold `(a == 1 && b != 0) || (a != 0 && b == 0))` to `(a ==
zjaffal Jun 9, 2024
c2b0197
generalise compare
zjaffal Jun 19, 2024
371770c
update test cases
zjaffal Jun 19, 2024
1c0318d
simplify the compare
zjaffal Jun 19, 2024
17ad22a
use correct inversions
zjaffal Jun 19, 2024
6b5a689
use inv(cmp2) and update test cases
zjaffal Jun 20, 2024
9dd61c6
address nit comments
zjaffal Jun 21, 2024
ff02d06
address nit
zjaffal Jun 23, 2024
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24 changes: 24 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3421,6 +3421,25 @@ Value *InstCombinerImpl::foldAndOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
return foldAndOrOfICmpsUsingRanges(LHS, RHS, IsAnd);
}

static Value *foldOrOfInversions(BinaryOperator &I,
InstCombiner::BuilderTy &Builder) {
assert(I.getOpcode() == Instruction::Or &&
"Simplification only supports or at the moment.");

Value *Cmp1, *Cmp2, *Cmp3, *Cmp4;
if (!match(I.getOperand(0), m_And(m_Value(Cmp1), m_Value(Cmp2))) ||
!match(I.getOperand(1), m_And(m_Value(Cmp3), m_Value(Cmp4))))
return nullptr;

// Check if any two pairs of the and operations are inversions of each other.
if (isKnownInversion(Cmp1, Cmp3) && isKnownInversion(Cmp2, Cmp4))
return Builder.CreateXor(Cmp1, Cmp4);
if (isKnownInversion(Cmp1, Cmp4) && isKnownInversion(Cmp2, Cmp3))
return Builder.CreateXor(Cmp1, Cmp3);

return nullptr;
}

// FIXME: We use commutative matchers (m_c_*) for some, but not all, matches
// here. We should standardize that construct where it is needed or choose some
// other way to ensure that commutated variants of patterns are not missed.
Expand Down Expand Up @@ -3450,6 +3469,11 @@ Instruction *InstCombinerImpl::visitOr(BinaryOperator &I) {
if (Instruction *X = foldComplexAndOrPatterns(I, Builder))
return X;

// (A & B) | (C & D) -> A ^ D where A == ~C && B == ~D
// (A & B) | (C & D) -> A ^ C where A == ~D && B == ~C
if (Value *V = foldOrOfInversions(I, Builder))
return replaceInstUsesWith(I, V);

// (A&B)|(A&C) -> A&(B|C) etc
if (Value *V = foldUsingDistributiveLaws(I))
return replaceInstUsesWith(I, V);
Expand Down
145 changes: 145 additions & 0 deletions llvm/test/Transforms/InstCombine/fold-a-or-b-zero.ll
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@@ -0,0 +1,145 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt < %s -S -passes=instcombine | FileCheck %s

declare void @use(i1)

define i1 @a_or_b(i32 %a, i32 %b) {
; CHECK-LABEL: define i1 @a_or_b(
; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i32 [[A]], 0
; CHECK-NEXT: [[TMP2:%.*]] = icmp eq i32 [[B]], 0
; CHECK-NEXT: [[OR:%.*]] = xor i1 [[TMP1]], [[TMP2]]
; CHECK-NEXT: ret i1 [[OR]]
;
%a_eq_zero = icmp eq i32 %a, 0
%b_ne_zero = icmp ne i32 %b, 0
%and.1 = and i1 %a_eq_zero, %b_ne_zero
%a_ne_zero = icmp ne i32 %a, 0
%b_eq_zero = icmp eq i32 %b, 0
%and.2 = and i1 %a_ne_zero, %b_eq_zero
%or = or i1 %and.1, %and.2
ret i1 %or
}

define i1 @a_or_b_not_inv(i32 %a, i32 %b){
; CHECK-LABEL: define i1 @a_or_b_not_inv(
; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
; CHECK-NEXT: [[A_EQ_ZERO:%.*]] = icmp eq i32 [[A]], 0
; CHECK-NEXT: [[B_NE_ZERO:%.*]] = icmp ne i32 [[B]], 0
; CHECK-NEXT: [[AND_1:%.*]] = and i1 [[A_EQ_ZERO]], [[B_NE_ZERO]]
; CHECK-NEXT: [[A_NE_ZERO:%.*]] = icmp ne i32 [[A]], 0
; CHECK-NEXT: [[B_EQ_1:%.*]] = icmp eq i32 [[B]], 1
; CHECK-NEXT: [[AND_2:%.*]] = and i1 [[A_NE_ZERO]], [[B_EQ_1]]
; CHECK-NEXT: [[OR:%.*]] = or i1 [[AND_1]], [[AND_2]]
; CHECK-NEXT: ret i1 [[OR]]
;
%a_eq_zero = icmp eq i32 %a, 0
%b_ne_zero = icmp ne i32 %b, 0
%and.1 = and i1 %a_eq_zero, %b_ne_zero
%a_ne_zero = icmp ne i32 %a, 0
%b_eq_1 = icmp eq i32 %b, 1
%and.2 = and i1 %a_ne_zero, %b_eq_1
%or = or i1 %and.1, %and.2
ret i1 %or
}

define i1 @a_or_b_const(i32 %a, i32 %b, i32 %c) {
; CHECK-LABEL: define i1 @a_or_b_const(
; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]], i32 [[C:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i32 [[A]], [[C]]
; CHECK-NEXT: [[TMP2:%.*]] = icmp eq i32 [[B]], [[C]]
; CHECK-NEXT: [[OR:%.*]] = xor i1 [[TMP1]], [[TMP2]]
; CHECK-NEXT: ret i1 [[OR]]
;
%a_eq_c = icmp eq i32 %a, %c
%b_ne_c = icmp ne i32 %b, %c
%and.1 = and i1 %a_eq_c, %b_ne_c
%a_ne_c = icmp ne i32 %a, %c
%b_eq_c = icmp eq i32 %b, %c
%and.2 = and i1 %a_ne_c, %b_eq_c
%or = or i1 %and.1, %and.2
ret i1 %or
}

define i1 @a_or_b_const2(i32 %a, i32 %b, i32 %c, i32 %d) {
; CHECK-LABEL: define i1 @a_or_b_const2(
; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]], i32 [[C:%.*]], i32 [[D:%.*]]) {
; CHECK-NEXT: [[A_EQ_C:%.*]] = icmp eq i32 [[A]], [[C]]
; CHECK-NEXT: [[B_EQ_D:%.*]] = icmp eq i32 [[B]], [[D]]
; CHECK-NEXT: [[OR:%.*]] = xor i1 [[A_EQ_C]], [[B_EQ_D]]
; CHECK-NEXT: ret i1 [[OR]]
;
%a_eq_c = icmp eq i32 %a, %c
%b_ne_d = icmp ne i32 %b, %d
%and.1 = and i1 %a_eq_c, %b_ne_d
%a_ne_c = icmp ne i32 %a, %c
%b_eq_d = icmp eq i32 %b, %d
%and.2 = and i1 %a_ne_c, %b_eq_d
%or = or i1 %and.1, %and.2
ret i1 %or
}
define i1 @a_or_b_nullptr(ptr %a, ptr %b) {
; CHECK-LABEL: define i1 @a_or_b_nullptr(
; CHECK-SAME: ptr [[A:%.*]], ptr [[B:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp eq ptr [[A]], null
; CHECK-NEXT: [[TMP2:%.*]] = icmp eq ptr [[B]], null
; CHECK-NEXT: [[OR:%.*]] = xor i1 [[TMP1]], [[TMP2]]
; CHECK-NEXT: ret i1 [[OR]]
;
%a_null = icmp eq ptr %a, null
%b_null = icmp eq ptr %b, null
%a_not_null = icmp ne ptr %a, null
%b_not_null = icmp ne ptr %b, null
%and.1 = and i1 %a_null, %b_not_null
%and.2 = and i1 %a_not_null, %b_null
%or = or i1 %and.1, %and.2
ret i1 %or
}

define i1 @a_or_b_multiple_uses(i32 %a, i32 %b) {
; CHECK-LABEL: define i1 @a_or_b_multiple_uses(
; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i32 [[A]], 0
; CHECK-NEXT: [[A_NE_ZERO:%.*]] = icmp ne i32 [[A]], 0
; CHECK-NEXT: [[B_EQ_ZERO:%.*]] = icmp eq i32 [[B]], 0
; CHECK-NEXT: [[AND_2:%.*]] = and i1 [[A_NE_ZERO]], [[B_EQ_ZERO]]
; CHECK-NEXT: call void @use(i1 [[AND_2]])
; CHECK-NEXT: [[OR:%.*]] = xor i1 [[TMP1]], [[B_EQ_ZERO]]
; CHECK-NEXT: ret i1 [[OR]]
;
%a_eq_zero = icmp eq i32 %a, 0
%b_ne_zero = icmp ne i32 %b, 0
%and.1 = and i1 %a_eq_zero, %b_ne_zero
%a_ne_zero = icmp ne i32 %a, 0
%b_eq_zero = icmp eq i32 %b, 0
%and.2 = and i1 %a_ne_zero, %b_eq_zero
call void @use(i1 %and.2)
%or = or i1 %and.1, %and.2
ret i1 %or
}

define i1 @a_or_b_multiple_uses_2(i32 %a, i32 %b) {
; CHECK-LABEL: define i1 @a_or_b_multiple_uses_2(
; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
; CHECK-NEXT: [[A_EQ_ZERO:%.*]] = icmp eq i32 [[A]], 0
; CHECK-NEXT: [[B_NE_ZERO:%.*]] = icmp ne i32 [[B]], 0
; CHECK-NEXT: call void @use(i1 [[B_NE_ZERO]])
; CHECK-NEXT: [[AND_1:%.*]] = and i1 [[A_EQ_ZERO]], [[B_NE_ZERO]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i32 [[B]], 0
; CHECK-NEXT: call void @use(i1 [[AND_1]])
; CHECK-NEXT: [[OR:%.*]] = xor i1 [[A_EQ_ZERO]], [[TMP1]]
; CHECK-NEXT: ret i1 [[OR]]
;
%a_eq_zero = icmp eq i32 %a, 0
%b_ne_zero = icmp ne i32 %b, 0
call void @use(i1 %b_ne_zero)
%and.1 = and i1 %a_eq_zero, %b_ne_zero
%a_ne_zero = icmp ne i32 %a, 0
%b_eq_zero = icmp eq i32 %b, 0
%and.2 = and i1 %a_ne_zero, %b_eq_zero
call void @use(i1 %and.1)
%or = or i1 %and.1, %and.2
ret i1 %or
}


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