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Transform (zext (or (icmp), (icmp))) to (or (zext (cimp), (zext icmp))) if at least one of the (zext icmp) can be transformed to eliminate an icmp. 

llvm-svn: 48715
This commit is contained in:
Evan Cheng 2008-03-24 00:21:34 +00:00
parent 58db865d6e
commit c3cf9f872a
2 changed files with 164 additions and 96 deletions
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225
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -236,6 +236,8 @@ namespace {
Instruction *visitCallSite(CallSite CS);
bool transformConstExprCastCall(CallSite CS);
Instruction *transformCallThroughTrampoline(CallSite CS);
Instruction *transformZExtICmp(ICmpInst *ICI, Instruction &CI,
bool DoXform = true);
public:
// InsertNewInstBefore - insert an instruction New before instruction Old
@ -4363,18 +4365,22 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
if (CastInst *Op0C = dyn_cast<CastInst>(Op0)) {
if (CastInst *Op1C = dyn_cast<CastInst>(Op1))
if (Op0C->getOpcode() == Op1C->getOpcode()) {// same cast kind ?
const Type *SrcTy = Op0C->getOperand(0)->getType();
if (SrcTy == Op1C->getOperand(0)->getType() && SrcTy->isInteger() &&
// Only do this if the casts both really cause code to be generated.
ValueRequiresCast(Op0C->getOpcode(), Op0C->getOperand(0),
I.getType(), TD) &&
ValueRequiresCast(Op1C->getOpcode(), Op1C->getOperand(0),
I.getType(), TD)) {
Instruction *NewOp = BinaryOperator::createOr(Op0C->getOperand(0),
Op1C->getOperand(0),
I.getName());
InsertNewInstBefore(NewOp, I);
return CastInst::create(Op0C->getOpcode(), NewOp, I.getType());
if (!isa<ICmpInst>(Op0C->getOperand(0)) ||
!isa<ICmpInst>(Op1C->getOperand(0))) {
const Type *SrcTy = Op0C->getOperand(0)->getType();
if (SrcTy == Op1C->getOperand(0)->getType() && SrcTy->isInteger() &&
// Only do this if the casts both really cause code to be
// generated.
ValueRequiresCast(Op0C->getOpcode(), Op0C->getOperand(0),
I.getType(), TD) &&
ValueRequiresCast(Op1C->getOpcode(), Op1C->getOperand(0),
I.getType(), TD)) {
Instruction *NewOp = BinaryOperator::createOr(Op0C->getOperand(0),
Op1C->getOperand(0),
I.getName());
InsertNewInstBefore(NewOp, I);
return CastInst::create(Op0C->getOpcode(), NewOp, I.getType());
}
}
}
}
@ -7188,6 +7194,101 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
return 0;
}
/// transformZExtICmp - Transform (zext icmp) to bitwise / integer operations
/// in order to eliminate the icmp.
Instruction *InstCombiner::transformZExtICmp(ICmpInst *ICI, Instruction &CI,
bool DoXform) {
// If we are just checking for a icmp eq of a single bit and zext'ing it
// 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();
// zext (x <s 0) to i32 --> x>>u31 true if signbit set.
// zext (x >s -1) to i32 --> (x>>u31)^1 true if signbit clear.
if ((ICI->getPredicate() == ICmpInst::ICMP_SLT && Op1CV == 0) ||
(ICI->getPredicate() == ICmpInst::ICMP_SGT &&Op1CV.isAllOnesValue())) {
if (!DoXform) return ICI;
Value *In = ICI->getOperand(0);
Value *Sh = ConstantInt::get(In->getType(),
In->getType()->getPrimitiveSizeInBits()-1);
In = InsertNewInstBefore(BinaryOperator::createLShr(In, Sh,
In->getName()+".lobit"),
CI);
if (In->getType() != CI.getType())
In = CastInst::createIntegerCast(In, CI.getType(),
false/*ZExt*/, "tmp", &CI);
if (ICI->getPredicate() == ICmpInst::ICMP_SGT) {
Constant *One = ConstantInt::get(In->getType(), 1);
In = InsertNewInstBefore(BinaryOperator::createXor(In, One,
In->getName()+".not"),
CI);
}
return ReplaceInstUsesWith(CI, In);
}
// 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()) {
// If Op1C some other power of two, convert:
uint32_t BitWidth = Op1C->getType()->getBitWidth();
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
APInt TypeMask(APInt::getAllOnesValue(BitWidth));
ComputeMaskedBits(ICI->getOperand(0), TypeMask, KnownZero, KnownOne);
APInt KnownZeroMask(~KnownZero);
if (KnownZeroMask.isPowerOf2()) { // Exactly 1 possible 1?
if (!DoXform) return ICI;
bool isNE = ICI->getPredicate() == ICmpInst::ICMP_NE;
if (Op1CV != 0 && (Op1CV != KnownZeroMask)) {
// (X&4) == 2 --> false
// (X&4) != 2 --> true
Constant *Res = ConstantInt::get(Type::Int1Ty, isNE);
Res = ConstantExpr::getZExt(Res, CI.getType());
return ReplaceInstUsesWith(CI, Res);
}
uint32_t ShiftAmt = KnownZeroMask.logBase2();
Value *In = ICI->getOperand(0);
if (ShiftAmt) {
// Perform a logical shr by shiftamt.
// Insert the shift to put the result in the low bit.
In = InsertNewInstBefore(BinaryOperator::createLShr(In,
ConstantInt::get(In->getType(), ShiftAmt),
In->getName()+".lobit"), CI);
}
if ((Op1CV != 0) == isNE) { // Toggle the low bit.
Constant *One = ConstantInt::get(In->getType(), 1);
In = BinaryOperator::createXor(In, One, "tmp");
InsertNewInstBefore(cast<Instruction>(In), CI);
}
if (CI.getType() == In->getType())
return ReplaceInstUsesWith(CI, In);
else
return CastInst::createIntegerCast(In, CI.getType(), false/*ZExt*/);
}
}
}
return 0;
}
Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
// If one of the common conversion will work ..
if (Instruction *Result = commonIntCastTransforms(CI))
@ -7224,92 +7325,24 @@ Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
}
}
if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src)) {
// If we are just checking for a icmp eq of a single bit and zext'ing it
// 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();
// zext (x <s 0) to i32 --> x>>u31 true if signbit set.
// zext (x >s -1) to i32 --> (x>>u31)^1 true if signbit clear.
if ((ICI->getPredicate() == ICmpInst::ICMP_SLT && Op1CV == 0) ||
(ICI->getPredicate() == ICmpInst::ICMP_SGT &&Op1CV.isAllOnesValue())){
Value *In = ICI->getOperand(0);
Value *Sh = ConstantInt::get(In->getType(),
In->getType()->getPrimitiveSizeInBits()-1);
In = InsertNewInstBefore(BinaryOperator::createLShr(In, Sh,
In->getName()+".lobit"),
CI);
if (In->getType() != CI.getType())
In = CastInst::createIntegerCast(In, CI.getType(),
false/*ZExt*/, "tmp", &CI);
if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src))
return transformZExtICmp(ICI, CI);
if (ICI->getPredicate() == ICmpInst::ICMP_SGT) {
Constant *One = ConstantInt::get(In->getType(), 1);
In = InsertNewInstBefore(BinaryOperator::createXor(In, One,
In->getName()+".not"),
CI);
}
return ReplaceInstUsesWith(CI, In);
}
// 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()) {
// If Op1C some other power of two, convert:
uint32_t BitWidth = Op1C->getType()->getBitWidth();
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
APInt TypeMask(APInt::getAllOnesValue(BitWidth));
ComputeMaskedBits(ICI->getOperand(0), TypeMask, KnownZero, KnownOne);
APInt KnownZeroMask(~KnownZero);
if (KnownZeroMask.isPowerOf2()) { // Exactly 1 possible 1?
bool isNE = ICI->getPredicate() == ICmpInst::ICMP_NE;
if (Op1CV != 0 && (Op1CV != KnownZeroMask)) {
// (X&4) == 2 --> false
// (X&4) != 2 --> true
Constant *Res = ConstantInt::get(Type::Int1Ty, isNE);
Res = ConstantExpr::getZExt(Res, CI.getType());
return ReplaceInstUsesWith(CI, Res);
}
uint32_t ShiftAmt = KnownZeroMask.logBase2();
Value *In = ICI->getOperand(0);
if (ShiftAmt) {
// Perform a logical shr by shiftamt.
// Insert the shift to put the result in the low bit.
In = InsertNewInstBefore(
BinaryOperator::createLShr(In,
ConstantInt::get(In->getType(), ShiftAmt),
In->getName()+".lobit"), CI);
}
if ((Op1CV != 0) == isNE) { // Toggle the low bit.
Constant *One = ConstantInt::get(In->getType(), 1);
In = BinaryOperator::createXor(In, One, "tmp");
InsertNewInstBefore(cast<Instruction>(In), CI);
}
if (CI.getType() == In->getType())
return ReplaceInstUsesWith(CI, In);
else
return CastInst::createIntegerCast(In, CI.getType(), false/*ZExt*/);
}
}
BinaryOperator *SrcI = dyn_cast<BinaryOperator>(Src);
if (SrcI && SrcI->getOpcode() == Instruction::Or) {
// zext (or icmp, icmp) --> or (zext icmp), (zext icmp) if at least one
// of the (zext icmp) will be transformed.
ICmpInst *LHS = dyn_cast<ICmpInst>(SrcI->getOperand(0));
ICmpInst *RHS = dyn_cast<ICmpInst>(SrcI->getOperand(1));
if (LHS && RHS && LHS->hasOneUse() && RHS->hasOneUse() &&
(transformZExtICmp(LHS, CI, false) ||
transformZExtICmp(RHS, CI, false))) {
Value *LCast = InsertCastBefore(Instruction::ZExt, LHS, CI.getType(), CI);
Value *RCast = InsertCastBefore(Instruction::ZExt, RHS, CI.getType(), CI);
return BinaryOperator::create(Instruction::Or, LCast, RCast);
}
}
}
return 0;
}

35
llvm/test/Transforms/InstCombine/zext-or-icmp.ll Normal file
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@ -0,0 +1,35 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep icmp | count 1
%struct.FooBar = type <{ i8, i8, [2 x i8], i8, i8, i8, i8, i16, i16, [4 x i8], [8 x %struct.Rock] }>
%struct.Rock = type { i16, i16 }
@some_idx = internal constant [4 x i8] c"\0A\0B\0E\0F" ; <[4 x i8]*> [#uses=1]
define i8 @t(%struct.FooBar* %up, i8 zeroext %intra_flag, i32 %blk_i) zeroext nounwind {
entry:
%tmp2 = lshr i32 %blk_i, 1 ; <i32> [#uses=1]
%tmp3 = and i32 %tmp2, 2 ; <i32> [#uses=1]
%tmp5 = and i32 %blk_i, 1 ; <i32> [#uses=1]
%tmp6 = or i32 %tmp3, %tmp5 ; <i32> [#uses=1]
%tmp8 = getelementptr %struct.FooBar* %up, i32 0, i32 7 ; <i16*> [#uses=1]
%tmp9 = load i16* %tmp8, align 1 ; <i16> [#uses=1]
%tmp910 = zext i16 %tmp9 to i32 ; <i32> [#uses=1]
%tmp12 = getelementptr [4 x i8]* @some_idx, i32 0, i32 %tmp6 ; <i8*> [#uses=1]
%tmp13 = load i8* %tmp12, align 1 ; <i8> [#uses=1]
%tmp1314 = zext i8 %tmp13 to i32 ; <i32> [#uses=1]
%tmp151 = lshr i32 %tmp910, %tmp1314 ; <i32> [#uses=1]
%tmp1516 = trunc i32 %tmp151 to i8 ; <i8> [#uses=1]
%tmp18 = getelementptr %struct.FooBar* %up, i32 0, i32 0 ; <i8*> [#uses=1]
%tmp19 = load i8* %tmp18, align 1 ; <i8> [#uses=1]
%tmp22 = and i8 %tmp1516, %tmp19 ; <i8> [#uses=1]
%tmp24 = getelementptr %struct.FooBar* %up, i32 0, i32 0 ; <i8*> [#uses=1]
%tmp25 = load i8* %tmp24, align 1 ; <i8> [#uses=1]
%tmp26.mask = and i8 %tmp25, 1 ; <i8> [#uses=1]
%toBool = icmp eq i8 %tmp26.mask, 0 ; <i1> [#uses=1]
%toBool.not = xor i1 %toBool, true ; <i1> [#uses=1]
%toBool33 = icmp eq i8 %intra_flag, 0 ; <i1> [#uses=1]
%bothcond = or i1 %toBool.not, %toBool33 ; <i1> [#uses=1]
%iftmp.1.0 = select i1 %bothcond, i8 0, i8 1 ; <i8> [#uses=1]
%tmp40 = or i8 %tmp22, %iftmp.1.0 ; <i8> [#uses=1]
%tmp432 = and i8 %tmp40, 1 ; <i8> [#uses=1]
ret i8 %tmp432
}