6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-06-24 08:24:33 +00:00
Code Issues Projects Releases Wiki Activity

recognize an unsigned add with overflow idiom into uadd.

Browse Source 
This resolves a README entry and technically resolves PR4916,
but we still get poor code for the testcase in that PR because
GVN isn't CSE'ing uadd with add, filed as PR8817.

Previously we got:

_test7:                                 ## @test7
	addq	%rsi, %rdi
	cmpq	%rdi, %rsi
	movl	$42, %eax
	cmovaq	%rsi, %rax
	ret

Now we get:

_test7:                                 ## @test7
	addq	%rsi, %rdi
	movl	$42, %eax
	cmovbq	%rsi, %rax
	ret



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122182 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2010-12-19 19:37:52 +00:00
parent 26b482d7a7
commit e5cbdca3bd
3 changed files with 85 additions and 25 deletions
Download Patch File Download Diff File Expand all files Collapse all files

55
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -1648,7 +1648,7 @@ static Instruction *ProcessUGT_ADDCST_ADD(ICmpInst &I, Value *A, Value *B,
// Put the new code above the original add, in case there are any uses of the
// add between the add and the compare.
Builder->SetInsertPoint(OrigAdd->getParent(), BasicBlock::iterator(OrigAdd));
Builder->SetInsertPoint(OrigAdd);
Value *TruncA = Builder->CreateTrunc(A, NewType, A->getName()+".trunc");
Value *TruncB = Builder->CreateTrunc(B, NewType, B->getName()+".trunc");
@ -1664,6 +1664,35 @@ 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 0;
// If the add is a constant expr, then we don't bother transforming it.
Instruction *OrigAdd = dyn_cast<Instruction>(OrigAddV);
if (OrigAdd == 0) return 0;
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();
const Type *Ty = LHS->getType();
Value *F = Intrinsic::getDeclaration(M, Intrinsic::uadd_with_overflow, &Ty,1);
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");
}
Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
bool Changed = false;
@ -1726,11 +1755,11 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
}
unsigned BitWidth = 0;
if (TD)
BitWidth = TD->getTypeSizeInBits(Ty->getScalarType());
else if (Ty->isIntOrIntVectorTy())
if (Ty->isIntOrIntVectorTy())
BitWidth = Ty->getScalarSizeInBits();
else if (TD) // Pointers require TD info to get their size.
BitWidth = TD->getTypeSizeInBits(Ty->getScalarType());
bool isSignBit = false;
// See if we are doing a comparison with a constant.
@ -2225,6 +2254,22 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
if (match(Op0, m_Not(m_Value(A))) &&
match(Op1, m_Not(m_Value(B))))
return new ICmpInst(I.getPredicate(), B, 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;
}
if (I.isEquality()) {