[llvm-commits] [llvm] r85038 - /llvm/trunk/lib/Analysis/ConstantFolding.cpp
Chris Lattner
sabre at nondot.org
Sat Oct 24 23:02:58 PDT 2009
Author: lattner
Date: Sun Oct 25 01:02:57 2009
New Revision: 85038
URL: http://llvm.org/viewvc/llvm-project?rev=85038&view=rev
Log:
refactor FoldBitCast to reduce nesting and to always return a constantexpr
instead of returning null on failure. No functionality change.
Modified:
llvm/trunk/lib/Analysis/ConstantFolding.cpp
Modified: llvm/trunk/lib/Analysis/ConstantFolding.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ConstantFolding.cpp?rev=85038&r1=85037&r2=85038&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ConstantFolding.cpp (original)
+++ llvm/trunk/lib/Analysis/ConstantFolding.cpp Sun Oct 25 01:02:57 2009
@@ -485,119 +485,125 @@
}
/// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
-/// targetdata. Return 0 if unfoldable.
+/// TargetData. This always returns a non-null constant, but it may be a
+/// ConstantExpr if unfoldable.
static Constant *FoldBitCast(Constant *C, const Type *DestTy,
const TargetData &TD, LLVMContext &Context) {
// If this is a bitcast from constant vector -> vector, fold it.
- if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
- if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
- // If the element types match, VMCore can fold it.
- unsigned NumDstElt = DestVTy->getNumElements();
- unsigned NumSrcElt = CV->getNumOperands();
- if (NumDstElt == NumSrcElt)
- return 0;
-
- const Type *SrcEltTy = CV->getType()->getElementType();
- const Type *DstEltTy = DestVTy->getElementType();
-
- // Otherwise, we're changing the number of elements in a vector, which
- // requires endianness information to do the right thing. For example,
- // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
- // folds to (little endian):
- // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
- // and to (big endian):
- // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
-
- // First thing is first. We only want to think about integer here, so if
- // we have something in FP form, recast it as integer.
- if (DstEltTy->isFloatingPoint()) {
- // Fold to an vector of integers with same size as our FP type.
- unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
- const Type *DestIVTy = VectorType::get(
- IntegerType::get(Context, FPWidth), NumDstElt);
- // Recursively handle this integer conversion, if possible.
- C = FoldBitCast(C, DestIVTy, TD, Context);
- if (!C) return 0;
+ ConstantVector *CV = dyn_cast<ConstantVector>(C);
+ if (CV == 0)
+ return ConstantExpr::getBitCast(C, DestTy);
+
+ const VectorType *DestVTy = dyn_cast<VectorType>(DestTy);
+ if (DestVTy == 0)
+ return ConstantExpr::getBitCast(C, DestTy);
+
+ // If the element types match, VMCore can fold it.
+ unsigned NumDstElt = DestVTy->getNumElements();
+ unsigned NumSrcElt = CV->getNumOperands();
+ if (NumDstElt == NumSrcElt)
+ return ConstantExpr::getBitCast(C, DestTy);
+
+ const Type *SrcEltTy = CV->getType()->getElementType();
+ const Type *DstEltTy = DestVTy->getElementType();
+
+ // Otherwise, we're changing the number of elements in a vector, which
+ // requires endianness information to do the right thing. For example,
+ // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
+ // folds to (little endian):
+ // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
+ // and to (big endian):
+ // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
+
+ // First thing is first. We only want to think about integer here, so if
+ // we have something in FP form, recast it as integer.
+ if (DstEltTy->isFloatingPoint()) {
+ // Fold to an vector of integers with same size as our FP type.
+ unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
+ const Type *DestIVTy = VectorType::get(
+ IntegerType::get(Context, FPWidth), NumDstElt);
+ // Recursively handle this integer conversion, if possible.
+ C = FoldBitCast(C, DestIVTy, TD, Context);
+ if (!C) return ConstantExpr::getBitCast(C, DestTy);
+
+ // Finally, VMCore can handle this now that #elts line up.
+ return ConstantExpr::getBitCast(C, DestTy);
+ }
+
+ // Okay, we know the destination is integer, if the input is FP, convert
+ // it to integer first.
+ if (SrcEltTy->isFloatingPoint()) {
+ unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
+ const Type *SrcIVTy = VectorType::get(
+ IntegerType::get(Context, FPWidth), NumSrcElt);
+ // Ask VMCore to do the conversion now that #elts line up.
+ C = ConstantExpr::getBitCast(C, SrcIVTy);
+ CV = dyn_cast<ConstantVector>(C);
+ if (!CV) // If VMCore wasn't able to fold it, bail out.
+ return C;
+ }
+
+ // Now we know that the input and output vectors are both integer vectors
+ // of the same size, and that their #elements is not the same. Do the
+ // conversion here, which depends on whether the input or output has
+ // more elements.
+ bool isLittleEndian = TD.isLittleEndian();
+
+ SmallVector<Constant*, 32> Result;
+ if (NumDstElt < NumSrcElt) {
+ // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
+ Constant *Zero = Constant::getNullValue(DstEltTy);
+ unsigned Ratio = NumSrcElt/NumDstElt;
+ unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
+ unsigned SrcElt = 0;
+ for (unsigned i = 0; i != NumDstElt; ++i) {
+ // Build each element of the result.
+ Constant *Elt = Zero;
+ unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
+ for (unsigned j = 0; j != Ratio; ++j) {
+ Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
+ if (!Src) // Reject constantexpr elements.
+ return ConstantExpr::getBitCast(C, DestTy);
- // Finally, VMCore can handle this now that #elts line up.
- return ConstantExpr::getBitCast(C, DestTy);
- }
-
- // Okay, we know the destination is integer, if the input is FP, convert
- // it to integer first.
- if (SrcEltTy->isFloatingPoint()) {
- unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
- const Type *SrcIVTy = VectorType::get(
- IntegerType::get(Context, FPWidth), NumSrcElt);
- // Ask VMCore to do the conversion now that #elts line up.
- C = ConstantExpr::getBitCast(C, SrcIVTy);
- CV = dyn_cast<ConstantVector>(C);
- if (!CV) return 0; // If VMCore wasn't able to fold it, bail out.
- }
-
- // Now we know that the input and output vectors are both integer vectors
- // of the same size, and that their #elements is not the same. Do the
- // conversion here, which depends on whether the input or output has
- // more elements.
- bool isLittleEndian = TD.isLittleEndian();
-
- SmallVector<Constant*, 32> Result;
- if (NumDstElt < NumSrcElt) {
- // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
- Constant *Zero = Constant::getNullValue(DstEltTy);
- unsigned Ratio = NumSrcElt/NumDstElt;
- unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
- unsigned SrcElt = 0;
- for (unsigned i = 0; i != NumDstElt; ++i) {
- // Build each element of the result.
- Constant *Elt = Zero;
- unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
- for (unsigned j = 0; j != Ratio; ++j) {
- Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
- if (!Src) return 0; // Reject constantexpr elements.
-
- // Zero extend the element to the right size.
- Src = ConstantExpr::getZExt(Src, Elt->getType());
-
- // Shift it to the right place, depending on endianness.
- Src = ConstantExpr::getShl(Src,
- ConstantInt::get(Src->getType(), ShiftAmt));
- ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
-
- // Mix it in.
- Elt = ConstantExpr::getOr(Elt, Src);
- }
- Result.push_back(Elt);
- }
- } else {
- // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
- unsigned Ratio = NumDstElt/NumSrcElt;
- unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
+ // Zero extend the element to the right size.
+ Src = ConstantExpr::getZExt(Src, Elt->getType());
- // Loop over each source value, expanding into multiple results.
- for (unsigned i = 0; i != NumSrcElt; ++i) {
- Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
- if (!Src) return 0; // Reject constantexpr elements.
-
- unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
- for (unsigned j = 0; j != Ratio; ++j) {
- // Shift the piece of the value into the right place, depending on
- // endianness.
- Constant *Elt = ConstantExpr::getLShr(Src,
- ConstantInt::get(Src->getType(), ShiftAmt));
- ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
-
- // Truncate and remember this piece.
- Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
- }
- }
+ // Shift it to the right place, depending on endianness.
+ Src = ConstantExpr::getShl(Src,
+ ConstantInt::get(Src->getType(), ShiftAmt));
+ ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
+
+ // Mix it in.
+ Elt = ConstantExpr::getOr(Elt, Src);
+ }
+ Result.push_back(Elt);
+ }
+ } else {
+ // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
+ unsigned Ratio = NumDstElt/NumSrcElt;
+ unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
+
+ // Loop over each source value, expanding into multiple results.
+ for (unsigned i = 0; i != NumSrcElt; ++i) {
+ Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
+ if (!Src) // Reject constantexpr elements.
+ return ConstantExpr::getBitCast(C, DestTy);
+
+ unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
+ for (unsigned j = 0; j != Ratio; ++j) {
+ // Shift the piece of the value into the right place, depending on
+ // endianness.
+ Constant *Elt = ConstantExpr::getLShr(Src,
+ ConstantInt::get(Src->getType(), ShiftAmt));
+ ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
+
+ // Truncate and remember this piece.
+ Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
}
-
- return ConstantVector::get(Result.data(), Result.size());
}
}
- return 0;
+ return ConstantVector::get(Result.data(), Result.size());
}
@@ -774,8 +780,7 @@
return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
case Instruction::BitCast:
if (TD)
- if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD, Context))
- return C;
+ return FoldBitCast(Ops[0], DestTy, *TD, Context);
return ConstantExpr::getBitCast(Ops[0], DestTy);
case Instruction::Select:
return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
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