[InstSimplify] simplify add instruction if two operands are negative

Differential Revision: https://reviews.llvm.org/D49216

llvm-svn: 336881
This commit is contained in:
Chen Zheng 2018-07-12 03:06:04 +00:00
parent 7fc1a1704e
commit c52635b197
4 changed files with 29 additions and 8 deletions

View File

@ -101,6 +101,9 @@ class Value;
const Instruction *CxtI = nullptr,
const DominatorTree *DT = nullptr);
/// Return true if the two given values are negation.
bool isKnownNegation(const Value *X, const Value *Y);
/// Returns true if the give value is known to be non-negative.
bool isKnownNonNegative(const Value *V, const DataLayout &DL,
unsigned Depth = 0,

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@ -540,6 +540,10 @@ static Value *SimplifyAddInst(Value *Op0, Value *Op1, bool IsNSW, bool IsNUW,
if (match(Op1, m_Zero()))
return Op0;
// If two operands are negative, return 0.
if (isKnownNegation(Op0, Op1))
return Constant::getNullValue(Op0->getType());
// X + (Y - X) -> Y
// (Y - X) + X -> Y
// Eg: X + -X -> 0

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@ -4511,6 +4511,26 @@ static SelectPatternResult matchMinMax(CmpInst::Predicate Pred,
return {SPF_UNKNOWN, SPNB_NA, false};
}
bool llvm::isKnownNegation(const Value *X, const Value *Y) {
assert(X && Y && "Invalid operand");
// X = sub (0, Y)
if (match(X, m_Neg(m_Specific(Y))))
return true;
// Y = sub (0, X)
if (match(Y, m_Neg(m_Specific(X))))
return true;
// X = sub (A, B), Y = sub (B, A)
Value *A, *B;
if (match(X, m_Sub(m_Value(A), m_Value(B))) &&
match(Y, m_Sub(m_Specific(B), m_Specific(A))))
return true;
return false;
}
static SelectPatternResult matchSelectPattern(CmpInst::Predicate Pred,
FastMathFlags FMF,
Value *CmpLHS, Value *CmpRHS,

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@ -30,10 +30,7 @@ define <2 x i32> @negated_operand_commute_vec(<2 x i32> %x) {
define i8 @knownnegation(i8 %x, i8 %y) {
; CHECK-LABEL: @knownnegation(
; CHECK-NEXT: [[XY:%.*]] = sub i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[YX:%.*]] = sub i8 [[Y]], [[X]]
; CHECK-NEXT: [[R:%.*]] = add i8 [[XY]], [[YX]]
; CHECK-NEXT: ret i8 [[R]]
; CHECK-NEXT: ret i8 0
;
%xy = sub i8 %x, %y
%yx = sub i8 %y, %x
@ -43,10 +40,7 @@ define i8 @knownnegation(i8 %x, i8 %y) {
define <2 x i8> @knownnegation_commute_vec(<2 x i8> %x, <2 x i8> %y) {
; CHECK-LABEL: @knownnegation_commute_vec(
; CHECK-NEXT: [[XY:%.*]] = sub <2 x i8> [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[YX:%.*]] = sub <2 x i8> [[Y]], [[X]]
; CHECK-NEXT: [[R:%.*]] = add <2 x i8> [[YX]], [[XY]]
; CHECK-NEXT: ret <2 x i8> [[R]]
; CHECK-NEXT: ret <2 x i8> zeroinitializer
;
%xy = sub <2 x i8> %x, %y
%yx = sub <2 x i8> %y, %x