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[CVP] Remove some {s|u}sub.with.overflow checks. 

This uses ConstantRange::makeGuaranteedNoWrapRegion's newly-added handling for subtraction to allow CVP to remove some subtraction overflow checks.

Differential Revision: https://reviews.llvm.org/D40039

llvm-svn: 319807
This commit is contained in:
Joel Galenson 2017-12-05 18:14:24 +00:00
parent c32b0fc249
commit ea0bafda8a
2 changed files with 23 additions and 15 deletions
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25
llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
View File

@ -329,13 +329,15 @@ static bool processSwitch(SwitchInst *SI, LazyValueInfo *LVI) {
// See if we can prove that the given overflow intrinsic will not overflow.
static bool willNotOverflow(IntrinsicInst *II, LazyValueInfo *LVI) {
using OBO = OverflowingBinaryOperator;
auto NoWrapOnAddition = [&] (Value *LHS, Value *RHS, unsigned NoWrapKind) {
auto NoWrap = [&] (Instruction::BinaryOps BinOp, unsigned NoWrapKind) {
Value *RHS = II->getOperand(1);
ConstantRange RRange = LVI->getConstantRange(RHS, II->getParent(), II);
ConstantRange NWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
BinaryOperator::Add, RRange, NoWrapKind);
BinOp, RRange, NoWrapKind);
// As an optimization, do not compute LRange if we do not need it.
if (NWRegion.isEmptySet())
return false;
Value *LHS = II->getOperand(0);
ConstantRange LRange = LVI->getConstantRange(LHS, II->getParent(), II);
return NWRegion.contains(LRange);
};
@ -343,11 +345,13 @@ static bool willNotOverflow(IntrinsicInst *II, LazyValueInfo *LVI) {
default:
break;
case Intrinsic::uadd_with_overflow:
return NoWrapOnAddition(II->getOperand(0), II->getOperand(1),
OBO::NoUnsignedWrap);
return NoWrap(Instruction::Add, OBO::NoUnsignedWrap);
case Intrinsic::sadd_with_overflow:
return NoWrapOnAddition(II->getOperand(0), II->getOperand(1),
OBO::NoSignedWrap);
return NoWrap(Instruction::Add, OBO::NoSignedWrap);
case Intrinsic::usub_with_overflow:
return NoWrap(Instruction::Sub, OBO::NoUnsignedWrap);
case Intrinsic::ssub_with_overflow:
return NoWrap(Instruction::Sub, OBO::NoSignedWrap);
}
return false;
}
@ -356,12 +360,17 @@ static void processOverflowIntrinsic(IntrinsicInst *II) {
Value *NewOp = nullptr;
switch (II->getIntrinsicID()) {
default:
llvm_unreachable("Illegal instruction.");
llvm_unreachable("Unexpected instruction.");
case Intrinsic::uadd_with_overflow:
case Intrinsic::sadd_with_overflow:
NewOp = BinaryOperator::CreateAdd(II->getOperand(0), II->getOperand(1),
II->getName(), II);
break;
case Intrinsic::usub_with_overflow:
case Intrinsic::ssub_with_overflow:
NewOp = BinaryOperator::CreateSub(II->getOperand(0), II->getOperand(1),
II->getName(), II);
break;
}
++NumOverflows;
IRBuilder<> B(II);
@ -376,7 +385,7 @@ static bool processCallSite(CallSite CS, LazyValueInfo *LVI) {
SmallVector<unsigned, 4> ArgNos;
unsigned ArgNo = 0;
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
if (auto *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
if (willNotOverflow(II, LVI)) {
processOverflowIntrinsic(II);
return true;

13
llvm/test/Transforms/CorrelatedValuePropagation/overflows.ll
View File

@ -13,8 +13,7 @@ declare void @llvm.trap()
define i32 @signed_add(i32 %x, i32 %y) {
; CHECK-LABEL: @signed_add(
; CHECK: @llvm.ssub.with.overflow.i32
; CHECK: @llvm.ssub.with.overflow.i32
; CHECK-NOT: @llvm.ssub.with.overflow.i32
; CHECK: @llvm.sadd.with.overflow.i32
entry:
%cmp = icmp sgt i32 %y, 0
@ -61,7 +60,7 @@ cond.end: ; preds = %cond.false, %cont,
define i32 @unsigned_add(i32 %x, i32 %y) {
; CHECK-LABEL: @unsigned_add(
; CHECK: @llvm.usub.with.overflow.i32
; CHECK-NOT: @llvm.usub.with.overflow.i32
; CHECK: @llvm.uadd.with.overflow.i32
entry:
%0 = tail call { i32, i1 } @llvm.usub.with.overflow.i32(i32 -1, i32 %y)
@ -203,7 +202,7 @@ cond.end: ; preds = %cond.false, %entry
define i32 @signed_sub_r1(i32 %x) {
; CHECK-LABEL: @signed_sub_r1(
; CHECK: @llvm.ssub.with.overflow.i32
; CHECK-NOT: @llvm.ssub.with.overflow.i32
entry:
%cmp = icmp eq i32 %x, -2147483648
br i1 %cmp, label %cond.end, label %cond.false
@ -225,7 +224,7 @@ cond.end: ; preds = %cond.false, %entry
define i32 @unsigned_sub_r1(i32 %x) {
; CHECK-LABEL: @unsigned_sub_r1(
; CHECK: @llvm.usub.with.overflow.i32
; CHECK-NOT: @llvm.usub.with.overflow.i32
entry:
%cmp = icmp eq i32 %x, 0
br i1 %cmp, label %cond.end, label %cond.false
@ -269,7 +268,7 @@ cond.end: ; preds = %cond.false, %entry
define i32 @signed_sub_rn1(i32 %x) {
; CHECK-LABEL: @signed_sub_rn1(
; CHECK: @llvm.ssub.with.overflow.i32
; CHECK-NOT: @llvm.ssub.with.overflow.i32
entry:
%cmp = icmp eq i32 %x, 2147483647
br i1 %cmp, label %cond.end, label %cond.false
@ -293,7 +292,7 @@ declare i32 @bar(i32)
define void @unsigned_loop(i32 %i) {
; CHECK-LABEL: @unsigned_loop(
; CHECK: @llvm.usub.with.overflow.i32
; CHECK-NOT: @llvm.usub.with.overflow.i32
entry:
%cmp3 = icmp eq i32 %i, 0
br i1 %cmp3, label %while.end, label %while.body.preheader