[llvm-commits] [llvm] r44855 - in /llvm/trunk: lib/Analysis/ConstantFolding.cpp test/Transforms/InstCombine/bitcast-vector-fold.ll
Chris Lattner
sabre at nondot.org
Mon Dec 10 23:29:44 PST 2007
Author: lattner
Date: Tue Dec 11 01:29:44 2007
New Revision: 44855
URL: http://llvm.org/viewvc/llvm-project?rev=44855&view=rev
Log:
Implement constant folding if vector<->vector bitcasts where the number
of source/dest elements changes. This implements
test/Transforms/InstCombine/bitcast-vector-fold.ll
Added:
llvm/trunk/test/Transforms/InstCombine/bitcast-vector-fold.ll
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=44855&r1=44854&r2=44855&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ConstantFolding.cpp (original)
+++ llvm/trunk/lib/Analysis/ConstantFolding.cpp Tue Dec 11 01:29:44 2007
@@ -145,6 +145,122 @@
return 0;
}
+/// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
+/// targetdata. Return 0 if unfoldable.
+static Constant *FoldBitCast(Constant *C, const Type *DestTy,
+ const TargetData &TD) {
+ // 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(FPWidth),
+ NumDstElt);
+ // Recursively handle this integer conversion, if possible.
+ C = FoldBitCast(C, DestIVTy, TD);
+ if (!C) return 0;
+
+ // 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(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();
+
+ // 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));
+ }
+ }
+ }
+
+ return ConstantVector::get(&Result[0], Result.size());
+ }
+ }
+
+ return 0;
+}
+
//===----------------------------------------------------------------------===//
// Constant Folding public APIs
@@ -233,7 +349,7 @@
return ConstantExpr::getIntegerCast(Input, DestTy, false);
}
}
- // FALL THROUGH.
+ return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
case Instruction::IntToPtr:
case Instruction::Trunc:
case Instruction::ZExt:
@@ -244,8 +360,12 @@
case Instruction::SIToFP:
case Instruction::FPToUI:
case Instruction::FPToSI:
+ return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
case Instruction::BitCast:
- return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
+ if (TD)
+ if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD))
+ return C;
+ return ConstantExpr::getBitCast(Ops[0], DestTy);
case Instruction::Select:
return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
case Instruction::ExtractElement:
Added: llvm/trunk/test/Transforms/InstCombine/bitcast-vector-fold.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/bitcast-vector-fold.ll?rev=44855&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/bitcast-vector-fold.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/bitcast-vector-fold.ll Tue Dec 11 01:29:44 2007
@@ -0,0 +1,33 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep bitcast
+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"
+target triple = "i686-apple-darwin8"
+
+define <2 x i64> @test1() {
+ %tmp3 = bitcast <4 x i32> < i32 0, i32 1, i32 2, i32 3 > to <2 x i64>
+ ret <2 x i64> %tmp3
+}
+
+define <4 x i32> @test2() {
+ %tmp3 = bitcast <2 x i64> < i64 0, i64 1 > to <4 x i32>
+ ret <4 x i32> %tmp3
+}
+
+define <2 x double> @test3() {
+ %tmp3 = bitcast <4 x i32> < i32 0, i32 1, i32 2, i32 3 > to <2 x double>
+ ret <2 x double> %tmp3
+}
+
+define <4 x float> @test4() {
+ %tmp3 = bitcast <2 x i64> < i64 0, i64 1 > to <4 x float>
+ ret <4 x float> %tmp3
+}
+
+define <2 x i64> @test5() {
+ %tmp3 = bitcast <4 x float> <float 0.0, float 1.0, float 2.0, float 3.0> to <2 x i64>
+ ret <2 x i64> %tmp3
+}
+
+define <4 x i32> @test6() {
+ %tmp3 = bitcast <2 x double> <double 0.5, double 1.0> to <4 x i32>
+ ret <4 x i32> %tmp3
+}
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