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274 lines
13 KiB
C++
274 lines
13 KiB
C++
//===-- SystemZSelectionDAGInfo.cpp - SystemZ SelectionDAG Info -----------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the SystemZSelectionDAGInfo class.
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//
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//===----------------------------------------------------------------------===//
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#include "SystemZTargetMachine.h"
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#include "llvm/CodeGen/SelectionDAG.h"
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using namespace llvm;
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#define DEBUG_TYPE "systemz-selectiondag-info"
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// Decide whether it is best to use a loop or straight-line code for
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// a block operation of Size bytes with source address Src and destination
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// address Dest. Sequence is the opcode to use for straight-line code
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// (such as MVC) and Loop is the opcode to use for loops (such as MVC_LOOP).
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// Return the chain for the completed operation.
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static SDValue emitMemMem(SelectionDAG &DAG, const SDLoc &DL, unsigned Sequence,
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unsigned Loop, SDValue Chain, SDValue Dst,
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SDValue Src, uint64_t Size) {
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EVT PtrVT = Src.getValueType();
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// The heuristic we use is to prefer loops for anything that would
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// require 7 or more MVCs. With these kinds of sizes there isn't
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// much to choose between straight-line code and looping code,
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// since the time will be dominated by the MVCs themselves.
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// However, the loop has 4 or 5 instructions (depending on whether
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// the base addresses can be proved equal), so there doesn't seem
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// much point using a loop for 5 * 256 bytes or fewer. Anything in
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// the range (5 * 256, 6 * 256) will need another instruction after
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// the loop, so it doesn't seem worth using a loop then either.
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// The next value up, 6 * 256, can be implemented in the same
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// number of straight-line MVCs as 6 * 256 - 1.
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if (Size > 6 * 256)
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return DAG.getNode(Loop, DL, MVT::Other, Chain, Dst, Src,
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DAG.getConstant(Size, DL, PtrVT),
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DAG.getConstant(Size / 256, DL, PtrVT));
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return DAG.getNode(Sequence, DL, MVT::Other, Chain, Dst, Src,
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DAG.getConstant(Size, DL, PtrVT));
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}
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SDValue SystemZSelectionDAGInfo::EmitTargetCodeForMemcpy(
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SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Dst, SDValue Src,
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SDValue Size, unsigned Align, bool IsVolatile, bool AlwaysInline,
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MachinePointerInfo DstPtrInfo, MachinePointerInfo SrcPtrInfo) const {
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if (IsVolatile)
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return SDValue();
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if (auto *CSize = dyn_cast<ConstantSDNode>(Size))
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return emitMemMem(DAG, DL, SystemZISD::MVC, SystemZISD::MVC_LOOP,
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Chain, Dst, Src, CSize->getZExtValue());
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return SDValue();
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}
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// Handle a memset of 1, 2, 4 or 8 bytes with the operands given by
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// Chain, Dst, ByteVal and Size. These cases are expected to use
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// MVI, MVHHI, MVHI and MVGHI respectively.
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static SDValue memsetStore(SelectionDAG &DAG, const SDLoc &DL, SDValue Chain,
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SDValue Dst, uint64_t ByteVal, uint64_t Size,
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unsigned Align, MachinePointerInfo DstPtrInfo) {
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uint64_t StoreVal = ByteVal;
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for (unsigned I = 1; I < Size; ++I)
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StoreVal |= ByteVal << (I * 8);
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return DAG.getStore(
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Chain, DL, DAG.getConstant(StoreVal, DL, MVT::getIntegerVT(Size * 8)),
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Dst, DstPtrInfo, Align);
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}
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SDValue SystemZSelectionDAGInfo::EmitTargetCodeForMemset(
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SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Dst,
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SDValue Byte, SDValue Size, unsigned Align, bool IsVolatile,
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MachinePointerInfo DstPtrInfo) const {
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EVT PtrVT = Dst.getValueType();
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if (IsVolatile)
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return SDValue();
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if (auto *CSize = dyn_cast<ConstantSDNode>(Size)) {
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uint64_t Bytes = CSize->getZExtValue();
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if (Bytes == 0)
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return SDValue();
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if (auto *CByte = dyn_cast<ConstantSDNode>(Byte)) {
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// Handle cases that can be done using at most two of
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// MVI, MVHI, MVHHI and MVGHI. The latter two can only be
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// used if ByteVal is all zeros or all ones; in other casees,
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// we can move at most 2 halfwords.
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uint64_t ByteVal = CByte->getZExtValue();
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if (ByteVal == 0 || ByteVal == 255 ?
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Bytes <= 16 && countPopulation(Bytes) <= 2 :
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Bytes <= 4) {
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unsigned Size1 = Bytes == 16 ? 8 : 1 << findLastSet(Bytes);
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unsigned Size2 = Bytes - Size1;
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SDValue Chain1 = memsetStore(DAG, DL, Chain, Dst, ByteVal, Size1,
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Align, DstPtrInfo);
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if (Size2 == 0)
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return Chain1;
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Dst = DAG.getNode(ISD::ADD, DL, PtrVT, Dst,
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DAG.getConstant(Size1, DL, PtrVT));
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DstPtrInfo = DstPtrInfo.getWithOffset(Size1);
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SDValue Chain2 = memsetStore(DAG, DL, Chain, Dst, ByteVal, Size2,
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std::min(Align, Size1), DstPtrInfo);
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return DAG.getNode(ISD::TokenFactor, DL, MVT::Other, Chain1, Chain2);
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}
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} else {
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// Handle one and two bytes using STC.
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if (Bytes <= 2) {
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SDValue Chain1 = DAG.getStore(Chain, DL, Byte, Dst, DstPtrInfo, Align);
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if (Bytes == 1)
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return Chain1;
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SDValue Dst2 = DAG.getNode(ISD::ADD, DL, PtrVT, Dst,
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DAG.getConstant(1, DL, PtrVT));
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SDValue Chain2 =
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DAG.getStore(Chain, DL, Byte, Dst2, DstPtrInfo.getWithOffset(1),
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/* Alignment = */ 1);
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return DAG.getNode(ISD::TokenFactor, DL, MVT::Other, Chain1, Chain2);
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}
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}
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assert(Bytes >= 2 && "Should have dealt with 0- and 1-byte cases already");
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// Handle the special case of a memset of 0, which can use XC.
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auto *CByte = dyn_cast<ConstantSDNode>(Byte);
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if (CByte && CByte->getZExtValue() == 0)
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return emitMemMem(DAG, DL, SystemZISD::XC, SystemZISD::XC_LOOP,
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Chain, Dst, Dst, Bytes);
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// Copy the byte to the first location and then use MVC to copy
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// it to the rest.
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Chain = DAG.getStore(Chain, DL, Byte, Dst, DstPtrInfo, Align);
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SDValue DstPlus1 = DAG.getNode(ISD::ADD, DL, PtrVT, Dst,
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DAG.getConstant(1, DL, PtrVT));
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return emitMemMem(DAG, DL, SystemZISD::MVC, SystemZISD::MVC_LOOP,
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Chain, DstPlus1, Dst, Bytes - 1);
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}
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return SDValue();
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}
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// Use CLC to compare [Src1, Src1 + Size) with [Src2, Src2 + Size),
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// deciding whether to use a loop or straight-line code.
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static SDValue emitCLC(SelectionDAG &DAG, const SDLoc &DL, SDValue Chain,
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SDValue Src1, SDValue Src2, uint64_t Size) {
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SDVTList VTs = DAG.getVTList(MVT::i32, MVT::Other);
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EVT PtrVT = Src1.getValueType();
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// A two-CLC sequence is a clear win over a loop, not least because it
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// needs only one branch. A three-CLC sequence needs the same number
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// of branches as a loop (i.e. 2), but is shorter. That brings us to
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// lengths greater than 768 bytes. It seems relatively likely that
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// a difference will be found within the first 768 bytes, so we just
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// optimize for the smallest number of branch instructions, in order
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// to avoid polluting the prediction buffer too much. A loop only ever
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// needs 2 branches, whereas a straight-line sequence would need 3 or more.
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if (Size > 3 * 256)
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return DAG.getNode(SystemZISD::CLC_LOOP, DL, VTs, Chain, Src1, Src2,
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DAG.getConstant(Size, DL, PtrVT),
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DAG.getConstant(Size / 256, DL, PtrVT));
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return DAG.getNode(SystemZISD::CLC, DL, VTs, Chain, Src1, Src2,
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DAG.getConstant(Size, DL, PtrVT));
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}
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// Convert the current CC value into an integer that is 0 if CC == 0,
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// less than zero if CC == 1 and greater than zero if CC >= 2.
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// The sequence starts with IPM, which puts CC into bits 29 and 28
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// of an integer and clears bits 30 and 31.
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static SDValue addIPMSequence(const SDLoc &DL, SDValue CCReg,
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SelectionDAG &DAG) {
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SDValue IPM = DAG.getNode(SystemZISD::IPM, DL, MVT::i32, CCReg);
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SDValue SRL = DAG.getNode(ISD::SRL, DL, MVT::i32, IPM,
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DAG.getConstant(SystemZ::IPM_CC, DL, MVT::i32));
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SDValue ROTL = DAG.getNode(ISD::ROTL, DL, MVT::i32, SRL,
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DAG.getConstant(31, DL, MVT::i32));
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return ROTL;
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}
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std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::EmitTargetCodeForMemcmp(
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SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Src1,
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SDValue Src2, SDValue Size, MachinePointerInfo Op1PtrInfo,
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MachinePointerInfo Op2PtrInfo) const {
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if (auto *CSize = dyn_cast<ConstantSDNode>(Size)) {
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uint64_t Bytes = CSize->getZExtValue();
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assert(Bytes > 0 && "Caller should have handled 0-size case");
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SDValue CCReg = emitCLC(DAG, DL, Chain, Src1, Src2, Bytes);
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Chain = CCReg.getValue(1);
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return std::make_pair(addIPMSequence(DL, CCReg, DAG), Chain);
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}
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return std::make_pair(SDValue(), SDValue());
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}
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std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::EmitTargetCodeForMemchr(
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SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Src,
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SDValue Char, SDValue Length, MachinePointerInfo SrcPtrInfo) const {
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// Use SRST to find the character. End is its address on success.
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EVT PtrVT = Src.getValueType();
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SDVTList VTs = DAG.getVTList(PtrVT, MVT::i32, MVT::Other);
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Length = DAG.getZExtOrTrunc(Length, DL, PtrVT);
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Char = DAG.getZExtOrTrunc(Char, DL, MVT::i32);
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Char = DAG.getNode(ISD::AND, DL, MVT::i32, Char,
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DAG.getConstant(255, DL, MVT::i32));
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SDValue Limit = DAG.getNode(ISD::ADD, DL, PtrVT, Src, Length);
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SDValue End = DAG.getNode(SystemZISD::SEARCH_STRING, DL, VTs, Chain,
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Limit, Src, Char);
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SDValue CCReg = End.getValue(1);
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Chain = End.getValue(2);
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// Now select between End and null, depending on whether the character
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// was found.
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SDValue Ops[] = {End, DAG.getConstant(0, DL, PtrVT),
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DAG.getConstant(SystemZ::CCMASK_SRST, DL, MVT::i32),
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DAG.getConstant(SystemZ::CCMASK_SRST_FOUND, DL, MVT::i32),
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CCReg};
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End = DAG.getNode(SystemZISD::SELECT_CCMASK, DL, PtrVT, Ops);
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return std::make_pair(End, Chain);
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}
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std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::EmitTargetCodeForStrcpy(
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SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Dest,
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SDValue Src, MachinePointerInfo DestPtrInfo, MachinePointerInfo SrcPtrInfo,
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bool isStpcpy) const {
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SDVTList VTs = DAG.getVTList(Dest.getValueType(), MVT::Other);
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SDValue EndDest = DAG.getNode(SystemZISD::STPCPY, DL, VTs, Chain, Dest, Src,
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DAG.getConstant(0, DL, MVT::i32));
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return std::make_pair(isStpcpy ? EndDest : Dest, EndDest.getValue(1));
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}
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std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::EmitTargetCodeForStrcmp(
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SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Src1,
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SDValue Src2, MachinePointerInfo Op1PtrInfo,
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MachinePointerInfo Op2PtrInfo) const {
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SDVTList VTs = DAG.getVTList(Src1.getValueType(), MVT::i32, MVT::Other);
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SDValue Unused = DAG.getNode(SystemZISD::STRCMP, DL, VTs, Chain, Src1, Src2,
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DAG.getConstant(0, DL, MVT::i32));
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SDValue CCReg = Unused.getValue(1);
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Chain = Unused.getValue(2);
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return std::make_pair(addIPMSequence(DL, CCReg, DAG), Chain);
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}
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// Search from Src for a null character, stopping once Src reaches Limit.
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// Return a pair of values, the first being the number of nonnull characters
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// and the second being the out chain.
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//
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// This can be used for strlen by setting Limit to 0.
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static std::pair<SDValue, SDValue> getBoundedStrlen(SelectionDAG &DAG,
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const SDLoc &DL,
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SDValue Chain, SDValue Src,
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SDValue Limit) {
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EVT PtrVT = Src.getValueType();
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SDVTList VTs = DAG.getVTList(PtrVT, MVT::i32, MVT::Other);
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SDValue End = DAG.getNode(SystemZISD::SEARCH_STRING, DL, VTs, Chain,
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Limit, Src, DAG.getConstant(0, DL, MVT::i32));
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Chain = End.getValue(2);
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SDValue Len = DAG.getNode(ISD::SUB, DL, PtrVT, End, Src);
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return std::make_pair(Len, Chain);
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}
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std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::EmitTargetCodeForStrlen(
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SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Src,
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MachinePointerInfo SrcPtrInfo) const {
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EVT PtrVT = Src.getValueType();
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return getBoundedStrlen(DAG, DL, Chain, Src, DAG.getConstant(0, DL, PtrVT));
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}
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std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::EmitTargetCodeForStrnlen(
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SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Src,
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SDValue MaxLength, MachinePointerInfo SrcPtrInfo) const {
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EVT PtrVT = Src.getValueType();
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MaxLength = DAG.getZExtOrTrunc(MaxLength, DL, PtrVT);
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SDValue Limit = DAG.getNode(ISD::ADD, DL, PtrVT, Src, MaxLength);
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return getBoundedStrlen(DAG, DL, Chain, Src, Limit);
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}
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