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[InstCombine][CodeGenPrep] Create llvm.uadd.with.overflow in CGP.

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Summary:
This change moves creating calls to `llvm.uadd.with.overflow` from
InstCombine to CodeGenPrep.  Combining overflow check patterns into
calls to the said intrinsic in InstCombine inhibits optimization because
it introduces an intrinsic call that not all other transforms and
analyses understand.

Depends on D8888.

Reviewers: majnemer, atrick

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8889

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234638 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjoy Das
2015-04-10 21:07:09 +00:00
parent 79db0a6fd9
commit 8aca90e5b6
6 changed files with 200 additions and 102 deletions
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56
lib/Transforms/InstCombine/InstCombineCompares.cpp
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@@ -2109,35 +2109,6 @@ static Instruction *ProcessUGT_ADDCST_ADD(ICmpInst &I, Value *A, Value *B,
return ExtractValueInst::Create(Call, 1, "sadd.overflow");
}
static Instruction *ProcessUAddIdiom(Instruction &I, Value *OrigAddV,
InstCombiner &IC) {
// Don't bother doing this transformation for pointers, don't do it for
// vectors.
if (!isa<IntegerType>(OrigAddV->getType())) return nullptr;
// If the add is a constant expr, then we don't bother transforming it.
Instruction *OrigAdd = dyn_cast<Instruction>(OrigAddV);
if (!OrigAdd) return nullptr;
Value *LHS = OrigAdd->getOperand(0), *RHS = OrigAdd->getOperand(1);
// Put the new code above the original add, in case there are any uses of the
// add between the add and the compare.
InstCombiner::BuilderTy *Builder = IC.Builder;
Builder->SetInsertPoint(OrigAdd);
Module *M = I.getParent()->getParent()->getParent();
Type *Ty = LHS->getType();
Value *F = Intrinsic::getDeclaration(M, Intrinsic::uadd_with_overflow, Ty);
CallInst *Call = Builder->CreateCall2(F, LHS, RHS, "uadd");
Value *Add = Builder->CreateExtractValue(Call, 0);
IC.ReplaceInstUsesWith(*OrigAdd, Add);
// The original icmp gets replaced with the overflow value.
return ExtractValueInst::Create(Call, 1, "uadd.overflow");
}
bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
Value *RHS, Instruction &OrigI,
Value *&Result, Constant *&Overflow) {
@@ -3539,21 +3510,18 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
return new ICmpInst(I.getPredicate(), ConstantExpr::getNot(RHSC), A);
}
// (a+b) <u a --> llvm.uadd.with.overflow.
// (a+b) <u b --> llvm.uadd.with.overflow.
if (I.getPredicate() == ICmpInst::ICMP_ULT &&
match(Op0, m_Add(m_Value(A), m_Value(B))) &&
(Op1 == A || Op1 == B))
if (Instruction *R = ProcessUAddIdiom(I, Op0, *this))
return R;
// a >u (a+b) --> llvm.uadd.with.overflow.
// b >u (a+b) --> llvm.uadd.with.overflow.
if (I.getPredicate() == ICmpInst::ICMP_UGT &&
match(Op1, m_Add(m_Value(A), m_Value(B))) &&
(Op0 == A || Op0 == B))
if (Instruction *R = ProcessUAddIdiom(I, Op1, *this))
return R;
Instruction *AddI = nullptr;
if (match(&I, m_UAddWithOverflow(m_Value(A), m_Value(B),
m_Instruction(AddI))) &&
isa<IntegerType>(A->getType())) {
Value *Result;
Constant *Overflow;
if (OptimizeOverflowCheck(OCF_UNSIGNED_ADD, A, B, *AddI, Result,
Overflow)) {
ReplaceInstUsesWith(*AddI, Result);
return ReplaceInstUsesWith(I, Overflow);
}
}
// (zext a) * (zext b) --> llvm.umul.with.overflow.
if (match(Op0, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {