6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-07-17 18:24:34 +00:00
Code Issues Projects Releases Wiki Activity

commit a tweaked version of Daniel's patch for PR3599. We now

Browse Source 
eliminate all the extensions and all but the one required truncate
from the testcase, but the or/and/shift stuff still isn't zapped.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64809 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2009-02-17 20:47:23 +00:00
parent 189c6357a1
commit a84f47c3e7
2 changed files with 52 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

55
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@@ -8271,32 +8271,35 @@ Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
Value *Src = CI.getOperand(0);
// If this is a cast of a cast
if (CastInst *CSrc = dyn_cast<CastInst>(Src)) { // A->B->C cast
// If this is a TRUNC followed by a ZEXT then we are dealing with integral
// types and if the sizes are just right we can convert this into a logical
// 'and' which will be much cheaper than the pair of casts.
if (isa<TruncInst>(CSrc)) {
// Get the sizes of the types involved
Value *A = CSrc->getOperand(0);
uint32_t SrcSize = A->getType()->getPrimitiveSizeInBits();
uint32_t MidSize = CSrc->getType()->getPrimitiveSizeInBits();
uint32_t DstSize = CI.getType()->getPrimitiveSizeInBits();
// If we're actually extending zero bits and the trunc is a no-op
if (MidSize < DstSize && SrcSize == DstSize) {
// Replace both of the casts with an And of the type mask.
APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
Constant *AndConst = ConstantInt::get(AndValue);
Instruction *And =
BinaryOperator::CreateAnd(CSrc->getOperand(0), AndConst);
// Unfortunately, if the type changed, we need to cast it back.
if (And->getType() != CI.getType()) {
And->setName(CSrc->getName()+".mask");
InsertNewInstBefore(And, CI);
And = CastInst::CreateIntegerCast(And, CI.getType(), false/*ZExt*/);
}
return And;
}
// If this is a TRUNC followed by a ZEXT then we are dealing with integral
// types and if the sizes are just right we can convert this into a logical
// 'and' which will be much cheaper than the pair of casts.
if (TruncInst *CSrc = dyn_cast<TruncInst>(Src)) { // A->B->C cast
// Get the sizes of the types involved. We know that the intermediate type
// will be smaller than A or C, but don't know the relation between A and C.
Value *A = CSrc->getOperand(0);
unsigned SrcSize = A->getType()->getPrimitiveSizeInBits();
unsigned MidSize = CSrc->getType()->getPrimitiveSizeInBits();
unsigned DstSize = CI.getType()->getPrimitiveSizeInBits();
// If we're actually extending zero bits, then if
// SrcSize < DstSize: zext(a & mask)
// SrcSize == DstSize: a & mask
// SrcSize > DstSize: trunc(a) & mask
if (SrcSize < DstSize) {
APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
Constant *AndConst = ConstantInt::get(AndValue);
Instruction *And =
BinaryOperator::CreateAnd(A, AndConst, CSrc->getName()+".mask");
InsertNewInstBefore(And, CI);
return new ZExtInst(And, CI.getType());
} else if (SrcSize == DstSize) {
APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
return BinaryOperator::CreateAnd(A, ConstantInt::get(AndValue));
} else if (SrcSize > DstSize) {
Instruction *Trunc = new TruncInst(A, CI.getType(), "tmp");
InsertNewInstBefore(Trunc, CI);
APInt AndValue(APInt::getLowBitsSet(DstSize, MidSize));
return BinaryOperator::CreateAnd(Trunc, ConstantInt::get(AndValue));
}
}