forked from OSchip/llvm-project
Implement constant folding if vector<->vector bitcasts where the number
of source/dest elements changes. This implements test/Transforms/InstCombine/bitcast-vector-fold.ll llvm-svn: 44855
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Chris Lattner
parent
0b1df1d3da
commit
6a6b3fb62b
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@ -145,6 +145,122 @@ static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
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return 0;
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}
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/// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
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/// targetdata. Return 0 if unfoldable.
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static Constant *FoldBitCast(Constant *C, const Type *DestTy,
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const TargetData &TD) {
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// If this is a bitcast from constant vector -> vector, fold it.
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if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
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if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
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// If the element types match, VMCore can fold it.
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unsigned NumDstElt = DestVTy->getNumElements();
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unsigned NumSrcElt = CV->getNumOperands();
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if (NumDstElt == NumSrcElt)
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return 0;
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const Type *SrcEltTy = CV->getType()->getElementType();
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const Type *DstEltTy = DestVTy->getElementType();
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// Otherwise, we're changing the number of elements in a vector, which
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// requires endianness information to do the right thing. For example,
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// bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
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// folds to (little endian):
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// <4 x i32> <i32 0, i32 0, i32 1, i32 0>
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// and to (big endian):
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// <4 x i32> <i32 0, i32 0, i32 0, i32 1>
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// First thing is first. We only want to think about integer here, so if
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// we have something in FP form, recast it as integer.
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if (DstEltTy->isFloatingPoint()) {
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// Fold to an vector of integers with same size as our FP type.
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unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
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const Type *DestIVTy = VectorType::get(IntegerType::get(FPWidth),
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NumDstElt);
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// Recursively handle this integer conversion, if possible.
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C = FoldBitCast(C, DestIVTy, TD);
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if (!C) return 0;
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// Finally, VMCore can handle this now that #elts line up.
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return ConstantExpr::getBitCast(C, DestTy);
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}
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// Okay, we know the destination is integer, if the input is FP, convert
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// it to integer first.
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if (SrcEltTy->isFloatingPoint()) {
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unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
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const Type *SrcIVTy = VectorType::get(IntegerType::get(FPWidth),
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NumSrcElt);
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// Ask VMCore to do the conversion now that #elts line up.
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C = ConstantExpr::getBitCast(C, SrcIVTy);
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CV = dyn_cast<ConstantVector>(C);
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if (!CV) return 0; // If VMCore wasn't able to fold it, bail out.
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}
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// Now we know that the input and output vectors are both integer vectors
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// of the same size, and that their #elements is not the same. Do the
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// conversion here, which depends on whether the input or output has
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// more elements.
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bool isLittleEndian = TD.isLittleEndian();
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SmallVector<Constant*, 32> Result;
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if (NumDstElt < NumSrcElt) {
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// Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
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Constant *Zero = Constant::getNullValue(DstEltTy);
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unsigned Ratio = NumSrcElt/NumDstElt;
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unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
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unsigned SrcElt = 0;
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for (unsigned i = 0; i != NumDstElt; ++i) {
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// Build each element of the result.
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Constant *Elt = Zero;
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unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
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for (unsigned j = 0; j != Ratio; ++j) {
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Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
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if (!Src) return 0; // Reject constantexpr elements.
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// Zero extend the element to the right size.
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Src = ConstantExpr::getZExt(Src, Elt->getType());
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// Shift it to the right place, depending on endianness.
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Src = ConstantExpr::getShl(Src,
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ConstantInt::get(Src->getType(), ShiftAmt));
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ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
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// Mix it in.
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Elt = ConstantExpr::getOr(Elt, Src);
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}
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Result.push_back(Elt);
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}
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} else {
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// Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
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unsigned Ratio = NumDstElt/NumSrcElt;
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unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
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// Loop over each source value, expanding into multiple results.
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for (unsigned i = 0; i != NumSrcElt; ++i) {
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Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
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if (!Src) return 0; // Reject constantexpr elements.
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unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
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for (unsigned j = 0; j != Ratio; ++j) {
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// Shift the piece of the value into the right place, depending on
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// endianness.
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Constant *Elt = ConstantExpr::getLShr(Src,
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ConstantInt::get(Src->getType(), ShiftAmt));
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ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
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// Truncate and remember this piece.
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Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
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}
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}
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}
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return ConstantVector::get(&Result[0], Result.size());
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}
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}
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return 0;
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}
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//===----------------------------------------------------------------------===//
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// Constant Folding public APIs
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@ -233,7 +349,7 @@ Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
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return ConstantExpr::getIntegerCast(Input, DestTy, false);
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}
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}
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// FALL THROUGH.
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return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
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case Instruction::IntToPtr:
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case Instruction::Trunc:
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case Instruction::ZExt:
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@ -244,8 +360,12 @@ Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
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case Instruction::SIToFP:
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case Instruction::FPToUI:
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case Instruction::FPToSI:
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return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
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case Instruction::BitCast:
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return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
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if (TD)
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if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD))
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return C;
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return ConstantExpr::getBitCast(Ops[0], DestTy);
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case Instruction::Select:
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return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
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case Instruction::ExtractElement:
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@ -0,0 +1,33 @@
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; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep bitcast
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target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
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target triple = "i686-apple-darwin8"
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define <2 x i64> @test1() {
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%tmp3 = bitcast <4 x i32> < i32 0, i32 1, i32 2, i32 3 > to <2 x i64>
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ret <2 x i64> %tmp3
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}
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define <4 x i32> @test2() {
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%tmp3 = bitcast <2 x i64> < i64 0, i64 1 > to <4 x i32>
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ret <4 x i32> %tmp3
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}
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define <2 x double> @test3() {
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%tmp3 = bitcast <4 x i32> < i32 0, i32 1, i32 2, i32 3 > to <2 x double>
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ret <2 x double> %tmp3
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}
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define <4 x float> @test4() {
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%tmp3 = bitcast <2 x i64> < i64 0, i64 1 > to <4 x float>
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ret <4 x float> %tmp3
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}
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define <2 x i64> @test5() {
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%tmp3 = bitcast <4 x float> <float 0.0, float 1.0, float 2.0, float 3.0> to <2 x i64>
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ret <2 x i64> %tmp3
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}
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define <4 x i32> @test6() {
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%tmp3 = bitcast <2 x double> <double 0.5, double 1.0> to <4 x i32>
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ret <4 x i32> %tmp3
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}
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