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[ValueTracking] Add support for xor/disjoint or in isKnownNonZero #87706

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[ValueTracking] Add support for xor/disjoint or in isKnownNonZero #87706

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9714cee
[ValueTracking] Add tests for `xor`/`disjoint or` in `isKnownNonZero`…
goldsteinn Apr 4, 2024
09907e5
[ValueTracking] Add support for `xor`/`disjoint or` in `isKnownNonZero`
goldsteinn Apr 3, 2024
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40 changes: 27 additions & 13 deletions llvm/lib/Analysis/ValueTracking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3092,20 +3092,33 @@ getInvertibleOperands(const Operator *Op1,
return std::nullopt;
}

/// Return true if V2 == V1 + X, where X is known non-zero.
static bool isAddOfNonZero(const Value *V1, const Value *V2, unsigned Depth,
const SimplifyQuery &Q) {
/// Return true if V1 == (binop V2, X), where X is known non-zero.
/// Only handle a small subset of binops where (binop V2, X) with non-zero X
/// implies V2 != V1.
static bool isModifyingBinopOfNonZero(const Value *V1, const Value *V2,
unsigned Depth, const SimplifyQuery &Q) {
const BinaryOperator *BO = dyn_cast<BinaryOperator>(V1);
if (!BO || BO->getOpcode() != Instruction::Add)
if (!BO)
return false;
Value *Op = nullptr;
if (V2 == BO->getOperand(0))
Op = BO->getOperand(1);
else if (V2 == BO->getOperand(1))
Op = BO->getOperand(0);
else
return false;
return isKnownNonZero(Op, Depth + 1, Q);
switch (BO->getOpcode()) {
default:
break;
case Instruction::Or:
if (!cast<PossiblyDisjointInst>(V1)->isDisjoint())
break;
[[fallthrough]];
case Instruction::Xor:
case Instruction::Add:
Value *Op = nullptr;
if (V2 == BO->getOperand(0))
Op = BO->getOperand(1);
else if (V2 == BO->getOperand(1))
Op = BO->getOperand(0);
else
return false;
return isKnownNonZero(Op, Depth + 1, Q);
}
return false;
}

/// Return true if V2 == V1 * C, where V1 is known non-zero, C is not 0/1 and
Expand Down Expand Up @@ -3265,7 +3278,8 @@ static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
};
}

if (isAddOfNonZero(V1, V2, Depth, Q) || isAddOfNonZero(V2, V1, Depth, Q))
if (isModifyingBinopOfNonZero(V1, V2, Depth, Q) ||
isModifyingBinopOfNonZero(V2, V1, Depth, Q))
return true;

if (isNonEqualMul(V1, V2, Depth, Q) || isNonEqualMul(V2, V1, Depth, Q))
Expand Down
61 changes: 60 additions & 1 deletion llvm/test/Transforms/InstSimplify/icmp.ll
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Expand Up @@ -270,11 +270,70 @@ define i1 @load_ptr(ptr %p) {

define i1 @load_ptr_null_valid(ptr %p) null_pointer_is_valid {
; CHECK-LABEL: @load_ptr_null_valid(
; CHECK-NEXT: [[LOAD_P:%.*]] = load ptr, ptr [[P:%.*]], align 8, !dereferenceable !0
; CHECK-NEXT: [[LOAD_P:%.*]] = load ptr, ptr [[P:%.*]], align 8, !dereferenceable [[META0:![0-9]+]]
; CHECK-NEXT: [[R:%.*]] = icmp ne ptr [[LOAD_P]], null
; CHECK-NEXT: ret i1 [[R]]
;
%load_p = load ptr, ptr %p, !dereferenceable !{i64 8}
%r = icmp ne ptr %load_p, null
ret i1 %r
}


define i1 @non_eq_disjoint_or(i8 %x, i8 %yy, i8 %w) {
; CHECK-LABEL: @non_eq_disjoint_or(
; CHECK-NEXT: ret i1 false
;
%y = add nuw i8 %yy, 1
%lhs = add i8 %x, %w
%val = or disjoint i8 %y, %w
%rhs = add i8 %x, %val
%r = icmp eq i8 %lhs, %rhs
ret i1 %r
}

define i1 @non_eq_or_fail(i8 %x, i8 %yy, i8 %w) {
; CHECK-LABEL: @non_eq_or_fail(
; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[YY:%.*]], 1
; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[W:%.*]]
; CHECK-NEXT: [[VAL:%.*]] = or i8 [[Y]], [[W]]
; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X]], [[VAL]]
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[LHS]], [[RHS]]
; CHECK-NEXT: ret i1 [[R]]
;
%y = add nuw i8 %yy, 1
%lhs = add i8 %x, %w
%val = or i8 %y, %w
%rhs = add i8 %x, %val
%r = icmp eq i8 %lhs, %rhs
ret i1 %r
}

define i1 @non_eq_xor(i8 %x, i8 %yy, i8 %w) {
; CHECK-LABEL: @non_eq_xor(
; CHECK-NEXT: ret i1 false
;
%y = add nuw i8 %yy, 1
%lhs = add i8 %x, %w
%val = xor i8 %y, %w
%rhs = add i8 %x, %val
%r = icmp eq i8 %lhs, %rhs
ret i1 %r
}

define i1 @non_eq_xor_fail(i8 %x, i8 %yy, i8 %w) {
; CHECK-LABEL: @non_eq_xor_fail(
; CHECK-NEXT: [[Y:%.*]] = add nsw i8 [[YY:%.*]], 1
; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[W:%.*]]
; CHECK-NEXT: [[VAL:%.*]] = xor i8 [[Y]], [[W]]
; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X]], [[VAL]]
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[LHS]], [[RHS]]
; CHECK-NEXT: ret i1 [[R]]
;
%y = add nsw i8 %yy, 1
%lhs = add i8 %x, %w
%val = xor i8 %y, %w
%rhs = add i8 %x, %val
%r = icmp eq i8 %lhs, %rhs
ret i1 %r
}