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improve comments, remove dead TD argument to CanEvaluateSExtd.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93143 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-01-11 02:43:35 +00:00
parent 11ea812424
commit 8cf4f6f3dd
1 changed files with 12 additions and 11 deletions
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23
lib/Transforms/InstCombine/InstCombineCasts.cpp
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@ -313,6 +313,8 @@ Instruction *InstCombiner::commonCastTransforms(CastInst &CI) {
/// then trunc(inst(x,y)) can be computed as inst(trunc(x),trunc(y)), which only
/// makes sense if x and y can be efficiently truncated.
///
/// This function works on both vectors and scalars.
///
static bool CanEvaluateTruncated(Value *V, const Type *Ty) {
// We can always evaluate constants in another type.
if (isa<Constant>(V))
@ -578,9 +580,9 @@ Instruction *InstCombiner::transformZExtICmp(ICmpInst *ICI, Instruction &CI,
}
/// CanEvaluateZExtd - Determine if the specified value can be computed in the
/// specified wider type and produce the same low bits. If not, return -1. If
/// it is possible, return the number of high bits that are known to be zero in
/// the promoted value.
/// specified wider type and produce the same low bits. If not, return false.
///
/// This function works on both vectors and scalars.
static bool CanEvaluateZExtd(Value *V, const Type *Ty, const TargetData *TD) {
if (isa<Constant>(V))
return true;
@ -780,7 +782,7 @@ Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
///
/// This function works on both vectors and scalars.
///
static bool CanEvaluateSExtd(Value *V, const Type *Ty, TargetData *TD) {
static bool CanEvaluateSExtd(Value *V, const Type *Ty) {
assert(V->getType()->getScalarSizeInBits() < Ty->getScalarSizeInBits() &&
"Can't sign extend type to a smaller type");
// If this is a constant, it can be trivially promoted.
@ -810,16 +812,15 @@ static bool CanEvaluateSExtd(Value *V, const Type *Ty, TargetData *TD) {
case Instruction::Sub:
case Instruction::Mul:
// These operators can all arbitrarily be extended if their inputs can.
return CanEvaluateSExtd(I->getOperand(0), Ty, TD) &&
CanEvaluateSExtd(I->getOperand(1), Ty, TD);
return CanEvaluateSExtd(I->getOperand(0), Ty) &&
CanEvaluateSExtd(I->getOperand(1), Ty);
//case Instruction::Shl: TODO
//case Instruction::LShr: TODO
//case Instruction::Trunc: TODO
case Instruction::Select:
return CanEvaluateSExtd(I->getOperand(1), Ty, TD) &&
CanEvaluateSExtd(I->getOperand(2), Ty, TD);
return CanEvaluateSExtd(I->getOperand(1), Ty) &&
CanEvaluateSExtd(I->getOperand(2), Ty);
case Instruction::PHI: {
// We can change a phi if we can change all operands. Note that we never
@ -827,7 +828,7 @@ static bool CanEvaluateSExtd(Value *V, const Type *Ty, TargetData *TD) {
// instructions with a single use.
PHINode *PN = cast<PHINode>(I);
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (!CanEvaluateSExtd(PN->getIncomingValue(i), Ty, TD)) return false;
if (!CanEvaluateSExtd(PN->getIncomingValue(i), Ty)) return false;
return true;
}
default:
@ -866,7 +867,7 @@ Instruction *InstCombiner::visitSExt(SExtInst &CI) {
// expression tree to something weird like i93 unless the source is also
// strange.
if ((isa<VectorType>(DestTy) || ShouldChangeType(SrcTy, DestTy)) &&
CanEvaluateSExtd(Src, DestTy, TD)) {
CanEvaluateSExtd(Src, DestTy)) {
// Okay, we can transform this! Insert the new expression now.
DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type"
" to avoid sign extend: " << CI);