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Implement Transforms/InstCombine/bswap.ll, turning common shift/and/or bswap

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idioms into bswap intrinsics.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28803 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-06-15 19:07:26 +00:00
parent c0ea2335f3
commit afe91a5f26
1 changed files with 131 additions and 1 deletions
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130
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -256,6 +256,7 @@ namespace {
Instruction *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
bool Inside, Instruction &IB);
Instruction *PromoteCastOfAllocation(CastInst &CI, AllocationInst &AI);
Instruction *MatchBSwap(BinaryOperator &I);
Value *EvaluateInDifferentType(Value *V, const Type *Ty);
};
@ -2791,6 +2792,128 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
return Changed ? &I : 0;
}
/// CollectBSwapParts - Look to see if the specified value defines a single byte
/// in the result. If it does, and if the specified byte hasn't been filled in
/// yet, fill it in and return false.
static bool CollectBSwapParts(Value *V, std::vector<Value*> &ByteValues) {
Instruction *I = dyn_cast<Instruction>(V);
if (I == 0) return true;
// If this is an or instruction, it is an inner node of the bswap.
if (I->getOpcode() == Instruction::Or)
return CollectBSwapParts(I->getOperand(0), ByteValues) ||
CollectBSwapParts(I->getOperand(1), ByteValues);
// If this is a shift by a constant int, and it is "24", then its operand
// defines a byte. We only handle unsigned types here.
if (isa<ShiftInst>(I) && isa<ConstantInt>(I->getOperand(1))) {
// Not shifting the entire input by N-1 bytes?
if (cast<ConstantInt>(I->getOperand(1))->getRawValue() !=
8*(ByteValues.size()-1))
return true;
unsigned DestNo;
if (I->getOpcode() == Instruction::Shl) {
// X << 24 defines the top byte with the lowest of the input bytes.
DestNo = ByteValues.size()-1;
} else {
// X >>u 24 defines the low byte with the highest of the input bytes.
DestNo = 0;
}
// If the destination byte value is already defined, the values are or'd
// together, which isn't a bswap (unless it's an or of the same bits).
if (ByteValues[DestNo] && ByteValues[DestNo] != I->getOperand(0))
return true;
ByteValues[DestNo] = I->getOperand(0);
return false;
}
// Otherwise, we can only handle and(shift X, imm), imm). Bail out of if we
// don't have this.
Value *Shift = 0, *ShiftLHS = 0;
ConstantInt *AndAmt = 0, *ShiftAmt = 0;
if (!match(I, m_And(m_Value(Shift), m_ConstantInt(AndAmt))) ||
!match(Shift, m_Shift(m_Value(ShiftLHS), m_ConstantInt(ShiftAmt))))
return true;
Instruction *SI = cast<Instruction>(Shift);
// Make sure that the shift amount is by a multiple of 8 and isn't too big.
if (ShiftAmt->getRawValue() & 7 ||
ShiftAmt->getRawValue() > 8*ByteValues.size())
return true;
// Turn 0xFF -> 0, 0xFF00 -> 1, 0xFF0000 -> 2, etc.
unsigned DestByte;
for (DestByte = 0; DestByte != ByteValues.size(); ++DestByte)
if (AndAmt->getRawValue() == uint64_t(0xFF) << 8*DestByte)
break;
// Unknown mask for bswap.
if (DestByte == ByteValues.size()) return true;
unsigned ShiftBytes = ShiftAmt->getRawValue()/8;
unsigned SrcByte;
if (SI->getOpcode() == Instruction::Shl)
SrcByte = DestByte - ShiftBytes;
else
SrcByte = DestByte + ShiftBytes;
// If the SrcByte isn't a bswapped value from the DestByte, reject it.
if (SrcByte != ByteValues.size()-DestByte-1)
return true;
// If the destination byte value is already defined, the values are or'd
// together, which isn't a bswap (unless it's an or of the same bits).
if (ByteValues[DestByte] && ByteValues[DestByte] != SI->getOperand(0))
return true;
ByteValues[DestByte] = SI->getOperand(0);
return false;
}
/// MatchBSwap - Given an OR instruction, check to see if this is a bswap idiom.
/// If so, insert the new bswap intrinsic and return it.
Instruction *InstCombiner::MatchBSwap(BinaryOperator &I) {
// We can only handle bswap of unsigned integers, and cannot bswap one byte.
if (!I.getType()->isUnsigned() || I.getType() == Type::UByteTy)
return 0;
/// ByteValues - For each byte of the result, we keep track of which value
/// defines each byte.
std::vector<Value*> ByteValues;
ByteValues.resize(I.getType()->getPrimitiveSize());
// Try to find all the pieces corresponding to the bswap.
if (CollectBSwapParts(I.getOperand(0), ByteValues) ||
CollectBSwapParts(I.getOperand(1), ByteValues))
return 0;
// Check to see if all of the bytes come from the same value.
Value *V = ByteValues[0];
if (V == 0) return 0; // Didn't find a byte? Must be zero.
// Check to make sure that all of the bytes come from the same value.
for (unsigned i = 1, e = ByteValues.size(); i != e; ++i)
if (ByteValues[i] != V)
return 0;
// If they do then *success* we can turn this into a bswap. Figure out what
// bswap to make it into.
Module *M = I.getParent()->getParent()->getParent();
const char *FnName;
if (I.getType() == Type::UShortTy)
FnName = "llvm.bswap.i16";
else if (I.getType() == Type::UIntTy)
FnName = "llvm.bswap.i32";
else if (I.getType() == Type::ULongTy)
FnName = "llvm.bswap.i64";
else
assert(0 && "Unknown integer type!");
Function *F = M->getOrInsertFunction(FnName, I.getType(), I.getType(), NULL);
return new CallInst(F, V);
}
Instruction *InstCombiner::visitOr(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
@ -2850,6 +2973,13 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
if (A == Op0 || B == Op0) // A | (A & ?) --> A
return ReplaceInstUsesWith(I, Op0);
// (A | B) | C and A | (B | C) -> bswap if possible.
if (match(Op0, m_Or(m_Value(), m_Value())) ||
match(Op1, m_Or(m_Value(), m_Value()))) {
if (Instruction *BSwap = MatchBSwap(I))
return BSwap;
}
// (X^C)|Y -> (X|Y)^C iff Y&C == 0
if (Op0->hasOneUse() && match(Op0, m_Xor(m_Value(A), m_ConstantInt(C1))) &&
MaskedValueIsZero(Op1, C1->getZExtValue())) {