From 71dddd51d928945d5ceb7e84322f2fe8244054d2 Mon Sep 17 00:00:00 2001 From: Bill Schmidt Date: Tue, 27 May 2014 15:57:51 +0000 Subject: [PATCH] Correct type used for VADD_SPLAT optimization on PowerPC In PPCISelLowering.cpp: PPCTargetLowering::LowerBUILD_VECTOR(), there is an optimization for certain patterns to generate one or two vector splats followed by a vector add or subtract. This operation is represented by a VADD_SPLAT in the selection DAG. Prior to this patch, it was possible for the VADD_SPLAT to be assigned the wrong data type, causing incorrect code generation. This patch corrects the problem. Specifically, the code previously assigned the value type of the BUILD_VECTOR node to the newly generated VADD_SPLAT node. This is correct much of the time, but not always. The problem is that the call to isConstantSplat() may return a SplatBitSize that is not the same as the number of bits in the original element vector type. The correct type to assign is a vector type with the same element bit size as SplatBitSize. The included test case shows an example of this, where the BUILD_VECTOR node has a type of v16i8. The vector to be built is {0, 16, 0, 16, 0, 16, 0, 16, 0, 16, 0, 16, 0, 16, 0, 16}. isConstantSplat detects that we can generate a splat of 16 for type v8i16, which is the type we must assign to the VADD_SPLAT node. If we do not, we generate a vspltisb of 8 and a vaddubm, which generates the incorrect result {16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16}. The correct code generation is a vspltish of 8 and a vadduhm. This patch also corrected code generation for CodeGen/PowerPC/2008-07-10-SplatMiscompile.ll, which had been marked as an XFAIL, so we can remove the XFAIL from the test case. llvm-svn: 209662 --- llvm/lib/Target/PowerPC/PPCISelLowering.cpp | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) (limited to 'llvm/lib/Target/PowerPC/PPCISelLowering.cpp') diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp index 214c8692060..cf4c9e61a58 100644 --- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp +++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp @@ -5531,10 +5531,14 @@ SDValue PPCTargetLowering::LowerBUILD_VECTOR(SDValue Op, // we convert to a pseudo that will be expanded later into one of // the above forms. SDValue Elt = DAG.getConstant(SextVal, MVT::i32); - EVT VT = Op.getValueType(); - int Size = VT == MVT::v16i8 ? 1 : (VT == MVT::v8i16 ? 2 : 4); - SDValue EltSize = DAG.getConstant(Size, MVT::i32); - return DAG.getNode(PPCISD::VADD_SPLAT, dl, VT, Elt, EltSize); + EVT VT = (SplatSize == 1 ? MVT::v16i8 : + (SplatSize == 2 ? MVT::v8i16 : MVT::v4i32)); + SDValue EltSize = DAG.getConstant(SplatSize, MVT::i32); + SDValue RetVal = DAG.getNode(PPCISD::VADD_SPLAT, dl, VT, Elt, EltSize); + if (VT == Op.getValueType()) + return RetVal; + else + return DAG.getNode(ISD::BITCAST, dl, Op.getValueType(), RetVal); } // If this is 0x8000_0000 x 4, turn into vspltisw + vslw. If it is -- cgit v1.2.3