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[InstrSimplify] fold sdiv if two operands are negated and non-overflow 

Differential Revision: https://reviews.llvm.org/D49382

llvm-svn: 337642
This commit is contained in:
Chen Zheng 2018-07-21 12:27:54 +00:00
parent 23c2d1c15a
commit 69bb064539
4 changed files with 28 additions and 34 deletions
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5
llvm/include/llvm/Analysis/ValueTracking.h
View File

@ -102,7 +102,10 @@ class Value;
const DominatorTree *DT = nullptr);
/// Return true if the two given values are negation.
bool isKnownNegation(const Value *X, const Value *Y);
/// Currently can recoginze Value pair:
/// 1: <X, Y> if X = sub (0, Y) or Y = sub (0, X)
/// 2: <X, Y> if X = sub (A, B) and Y = sub (B, A)
bool isKnownNegation(const Value *X, const Value *Y, bool NeedNSW = false);
/// Returns true if the give value is known to be non-negative.
bool isKnownNonNegative(const Value *V, const DataLayout &DL,

6
llvm/lib/Analysis/InstructionSimplify.cpp
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@ -1081,6 +1081,10 @@ static Value *simplifyRem(Instruction::BinaryOps Opcode, Value *Op0, Value *Op1,
/// If not, this returns null.
static Value *SimplifySDivInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
unsigned MaxRecurse) {
// If two operands are negated and no signed overflow, return -1.
if (isKnownNegation(Op0, Op1, /*NeedNSW=*/true))
return Constant::getAllOnesValue(Op0->getType());
return simplifyDiv(Instruction::SDiv, Op0, Op1, Q, MaxRecurse);
}
@ -1111,7 +1115,7 @@ static Value *SimplifySRemInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
// If the two operands are negated, return 0.
if (isKnownNegation(Op0, Op1))
return ConstantInt::getNullValue(Op0->getType());
return ConstantInt::getNullValue(Op0->getType());
return simplifyRem(Instruction::SRem, Op0, Op1, Q, MaxRecurse);
}

20
llvm/lib/Analysis/ValueTracking.cpp
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@ -4511,21 +4511,25 @@ static SelectPatternResult matchMinMax(CmpInst::Predicate Pred,
return {SPF_UNKNOWN, SPNB_NA, false};
}
bool llvm::isKnownNegation(const Value *X, const Value *Y) {
bool llvm::isKnownNegation(const Value *X, const Value *Y, bool NeedNSW) {
assert(X && Y && "Invalid operand");
// X = sub (0, Y)
if (match(X, m_Neg(m_Specific(Y))))
// X = sub (0, Y) || X = sub nsw (0, Y)
if ((!NeedNSW && match(X, m_Sub(m_ZeroInt(), m_Specific(Y)))) ||
(NeedNSW && match(X, m_NSWSub(m_ZeroInt(), m_Specific(Y)))))
return true;
// Y = sub (0, X)
if (match(Y, m_Neg(m_Specific(X))))
// Y = sub (0, X) || Y = sub nsw (0, X)
if ((!NeedNSW && match(Y, m_Sub(m_ZeroInt(), m_Specific(X)))) ||
(NeedNSW && match(Y, m_NSWSub(m_ZeroInt(), m_Specific(X)))))
return true;
// X = sub (A, B), Y = sub (B, A)
// X = sub (A, B), Y = sub (B, A) || X = sub nsw (A, B), Y = sub nsw (B, A)
Value *A, *B;
return match(X, m_Sub(m_Value(A), m_Value(B))) &&
match(Y, m_Sub(m_Specific(B), m_Specific(A)));
return (!NeedNSW && (match(X, m_Sub(m_Value(A), m_Value(B))) &&
match(Y, m_Sub(m_Specific(B), m_Specific(A))))) ||
(NeedNSW && (match(X, m_NSWSub(m_Value(A), m_Value(B))) &&
match(Y, m_NSWSub(m_Specific(B), m_Specific(A)))));
}
static SelectPatternResult matchSelectPattern(CmpInst::Predicate Pred,

31
llvm/test/Transforms/InstSimplify/sdiv.ll
View File

@ -3,9 +3,7 @@
define i32 @negated_operand(i32 %x) {
; CHECK-LABEL: @negated_operand(
; CHECK-NEXT: [[NEGX:%.*]] = sub nsw i32 0, [[X:%.*]]
; CHECK-NEXT: [[DIV:%.*]] = sdiv i32 [[NEGX]], [[X]]
; CHECK-NEXT: ret i32 [[DIV]]
; CHECK-NEXT: ret i32 -1
;
%negx = sub nsw i32 0, %x
%div = sdiv i32 %negx, %x
@ -14,9 +12,7 @@ define i32 @negated_operand(i32 %x) {
define <2 x i32> @negated_operand_commute_vec(<2 x i32> %x) {
; CHECK-LABEL: @negated_operand_commute_vec(
; CHECK-NEXT: [[NEGX:%.*]] = sub nsw <2 x i32> zeroinitializer, [[X:%.*]]
; CHECK-NEXT: [[DIV:%.*]] = sdiv <2 x i32> [[NEGX]], [[X]]
; CHECK-NEXT: ret <2 x i32> [[DIV]]
; CHECK-NEXT: ret <2 x i32> <i32 -1, i32 -1>
;
%negx = sub nsw <2 x i32> zeroinitializer, %x
%div = sdiv <2 x i32> %negx, %x
@ -25,10 +21,7 @@ define <2 x i32> @negated_operand_commute_vec(<2 x i32> %x) {
define i32 @knownnegation(i32 %x, i32 %y) {
; CHECK-LABEL: @knownnegation(
; CHECK-NEXT: [[XY:%.*]] = sub nsw i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[YX:%.*]] = sub nsw i32 [[Y]], [[X]]
; CHECK-NEXT: [[DIV:%.*]] = sdiv i32 [[XY]], [[YX]]
; CHECK-NEXT: ret i32 [[DIV]]
; CHECK-NEXT: ret i32 -1
;
%xy = sub nsw i32 %x, %y
%yx = sub nsw i32 %y, %x
@ -38,10 +31,7 @@ define i32 @knownnegation(i32 %x, i32 %y) {
define <2 x i32> @knownnegation_commute_vec(<2 x i32> %x, <2 x i32> %y) {
; CHECK-LABEL: @knownnegation_commute_vec(
; CHECK-NEXT: [[XY:%.*]] = sub nsw <2 x i32> [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[YX:%.*]] = sub nsw <2 x i32> [[Y]], [[X]]
; CHECK-NEXT: [[DIV:%.*]] = sdiv <2 x i32> [[XY]], [[YX]]
; CHECK-NEXT: ret <2 x i32> [[DIV]]
; CHECK-NEXT: ret <2 x i32> <i32 -1, i32 -1>
;
%xy = sub nsw <2 x i32> %x, %y
%yx = sub nsw <2 x i32> %y, %x
@ -51,10 +41,7 @@ define <2 x i32> @knownnegation_commute_vec(<2 x i32> %x, <2 x i32> %y) {
define i32 @negated_operand_2(i32 %t) {
; CHECK-LABEL: @negated_operand_2(
; CHECK-NEXT: [[X:%.*]] = sub i32 [[T:%.*]], 5
; CHECK-NEXT: [[NEGX:%.*]] = sub nsw i32 0, [[X]]
; CHECK-NEXT: [[DIV:%.*]] = sdiv i32 [[NEGX]], [[X]]
; CHECK-NEXT: ret i32 [[DIV]]
; CHECK-NEXT: ret i32 -1
;
%x = sub i32 %t, 5
%negx = sub nsw i32 0, %x
@ -64,9 +51,7 @@ define i32 @negated_operand_2(i32 %t) {
define i32 @negated_operand_commute(i32 %x) {
; CHECK-LABEL: @negated_operand_commute(
; CHECK-NEXT: [[NEGX:%.*]] = sub nsw i32 0, [[X]]
; CHECK-NEXT: [[DIV:%.*]] = sdiv i32 [[X]], [[NEGX]]
; CHECK-NEXT: ret i32 [[DIV]]
; CHECK-NEXT: ret i32 -1
;
%negx = sub nsw i32 0, %x
%div = sdiv i32 %x, %negx
@ -175,9 +160,7 @@ define <2 x i32> @knownnegation_commute_vec_bad3(<2 x i32> %x, <2 x i32> %y) {
define <3 x i32> @negated_operand_vec_undef(<3 x i32> %x) {
; CHECK-LABEL: @negated_operand_vec_undef(
; CHECK-NEXT: [[NEGX:%.*]] = sub nsw <3 x i32> <i32 0, i32 undef, i32 0>, [[X:%.*]]
; CHECK-NEXT: [[DIV:%.*]] = sdiv <3 x i32> [[NEGX]], [[X]]
; CHECK-NEXT: ret <3 x i32> [[DIV]]
; CHECK-NEXT: ret <3 x i32> <i32 -1, i32 -1, i32 -1>
;
%negx = sub nsw <3 x i32> <i32 0, i32 undef, i32 0>, %x
%div = sdiv <3 x i32> %negx, %x