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canonicalize (x <u 2147483648) -> (x >s -1) and (x >u 2147483647) -> (x <s 0)

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35886 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-04-11 06:12:58 +00:00
parent 66bc325bff
commit ba41783dbb
1 changed files with 32 additions and 25 deletions
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57
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -4624,6 +4624,11 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
return new ICmpInst(ICmpInst::ICMP_NE, Op0,Op1);
if (isMinValuePlusOne(CI,false)) // A <u MIN+1 -> A == MIN
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, SubOne(CI));
// (x <u 2147483648) -> (x >s -1) -> true if sign bit clear
if (CI->isMinValue(true))
return new ICmpInst(ICmpInst::ICMP_SGT, Op0,
ConstantInt::getAllOnesValue(Op0->getType()));
break;
case ICmpInst::ICMP_SLT:
@ -4642,6 +4647,11 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (isMaxValueMinusOne(CI, false)) // A >u MAX-1 -> A == MAX
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, AddOne(CI));
// (x >u 2147483647) -> (x <s 0) -> true if sign bit set
if (CI->isMaxValue(true))
return new ICmpInst(ICmpInst::ICMP_SLT, Op0,
ConstantInt::getNullValue(Op0->getType()));
break;
case ICmpInst::ICMP_SGT:
@ -6559,15 +6569,15 @@ Instruction *InstCombiner::visitZExt(CastInst &CI) {
// to an integer, then shift the bit to the appropriate place and then
// cast to integer to avoid the comparison.
if (ConstantInt *Op1C = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
const APInt& Op1CV = Op1C->getValue();
// cast (X == 0) to int --> X^1 iff X has only the low bit set.
// cast (X == 0) to int --> (X>>1)^1 iff X has only the 2nd bit set.
// cast (X == 1) to int --> X iff X has only the low bit set.
// cast (X == 2) to int --> X>>1 iff X has only the 2nd bit set.
// cast (X != 0) to int --> X iff X has only the low bit set.
// cast (X != 0) to int --> X>>1 iff X has only the 2nd bit set.
// cast (X != 1) to int --> X^1 iff X has only the low bit set.
// cast (X != 2) to int --> (X>>1)^1 iff X has only the 2nd bit set.
const APInt &Op1CV = Op1C->getValue();
// zext (X == 0) to i32 --> X^1 iff X has only the low bit set.
// zext (X == 0) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
// zext (X == 1) to i32 --> X iff X has only the low bit set.
// zext (X == 2) to i32 --> X>>1 iff X has only the 2nd bit set.
// zext (X != 0) to i32 --> X iff X has only the low bit set.
// zext (X != 0) to i32 --> X>>1 iff X has only the 2nd bit set.
// zext (X != 1) to i32 --> X^1 iff X has only the low bit set.
// zext (X != 2) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
if ((Op1CV == 0 || Op1CV.isPowerOf2()) &&
// This only works for EQ and NE
ICI->isEquality()) {
@ -6617,7 +6627,13 @@ Instruction *InstCombiner::visitZExt(CastInst &CI) {
}
Instruction *InstCombiner::visitSExt(CastInst &CI) {
return commonIntCastTransforms(CI);
if (Instruction *I = commonIntCastTransforms(CI))
return I;
// (x <s 0) ? -1 : 0 -> ashr x, 31
// (x >u 2147483647) ? -1 : 0 -> ashr x, 31
return 0;
}
Instruction *InstCombiner::visitFPTrunc(CastInst &CI) {
@ -6901,34 +6917,25 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
// Selecting between two integer constants?
if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
// select C, 1, 0 -> cast C to int
// select C, 1, 0 -> zext C to int
if (FalseValC->isZero() && TrueValC->getValue() == 1) {
return CastInst::create(Instruction::ZExt, CondVal, SI.getType());
} else if (TrueValC->isZero() && FalseValC->getValue() == 1) {
// select C, 0, 1 -> cast !C to int
// select C, 0, 1 -> zext !C to int
Value *NotCond =
InsertNewInstBefore(BinaryOperator::createNot(CondVal,
"not."+CondVal->getName()), SI);
return CastInst::create(Instruction::ZExt, NotCond, SI.getType());
}
// FIXME: Turn select 0/-1 and -1/0 into sext from condition!
if (ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition())) {
// (x <s 0) ? -1 : 0 -> ashr x, 31
// (x >u 2147483647) ? -1 : 0 -> ashr x, 31
if (TrueValC->isAllOnesValue() && FalseValC->isZero())
if (ConstantInt *CmpCst = dyn_cast<ConstantInt>(IC->getOperand(1))) {
bool CanXForm = false;
if (IC->isSignedPredicate())
CanXForm = CmpCst->isZero() &&
IC->getPredicate() == ICmpInst::ICMP_SLT;
else {
uint32_t Bits = CmpCst->getType()->getPrimitiveSizeInBits();
CanXForm = CmpCst->getValue() == APInt::getSignedMaxValue(Bits) &&
IC->getPredicate() == ICmpInst::ICMP_UGT;
}
if (CanXForm) {
if (IC->getPredicate() == ICmpInst::ICMP_SLT && CmpCst->isZero()) {
// The comparison constant and the result are not neccessarily the
// same width. Make an all-ones value by inserting a AShr.
Value *X = IC->getOperand(0);
@ -6953,7 +6960,7 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
// If one of the constants is zero (we know they can't both be) and we
// have a fcmp instruction with zero, and we have an 'and' with the
// have an icmp instruction with zero, and we have an 'and' with the
// non-constant value, eliminate this whole mess. This corresponds to
// cases like this: ((X & 27) ? 27 : 0)
if (TrueValC->isZero() || FalseValC->isZero())