//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "systemz-selectiondag-info"
#include "SystemZTargetMachine.h"
#include "llvm/CodeGen/SelectionDAG.h"
using namespace llvm;
-SystemZSelectionDAGInfo::
-SystemZSelectionDAGInfo(const SystemZTargetMachine &TM)
- : TargetSelectionDAGInfo(TM) {
-}
+#define DEBUG_TYPE "systemz-selectiondag-info"
+
+SystemZSelectionDAGInfo::SystemZSelectionDAGInfo(const DataLayout &DL)
+ : TargetSelectionDAGInfo(&DL) {}
SystemZSelectionDAGInfo::~SystemZSelectionDAGInfo() {
}
+// Decide whether it is best to use a loop or straight-line code for
+// a block operation of Size bytes with source address Src and destination
+// address Dest. Sequence is the opcode to use for straight-line code
+// (such as MVC) and Loop is the opcode to use for loops (such as MVC_LOOP).
+// Return the chain for the completed operation.
+static SDValue emitMemMem(SelectionDAG &DAG, SDLoc DL, unsigned Sequence,
+ unsigned Loop, SDValue Chain, SDValue Dst,
+ SDValue Src, uint64_t Size) {
+ EVT PtrVT = Src.getValueType();
+ // The heuristic we use is to prefer loops for anything that would
+ // require 7 or more MVCs. With these kinds of sizes there isn't
+ // much to choose between straight-line code and looping code,
+ // since the time will be dominated by the MVCs themselves.
+ // However, the loop has 4 or 5 instructions (depending on whether
+ // the base addresses can be proved equal), so there doesn't seem
+ // much point using a loop for 5 * 256 bytes or fewer. Anything in
+ // the range (5 * 256, 6 * 256) will need another instruction after
+ // the loop, so it doesn't seem worth using a loop then either.
+ // The next value up, 6 * 256, can be implemented in the same
+ // number of straight-line MVCs as 6 * 256 - 1.
+ if (Size > 6 * 256)
+ return DAG.getNode(Loop, DL, MVT::Other, Chain, Dst, Src,
+ DAG.getConstant(Size, PtrVT),
+ DAG.getConstant(Size / 256, PtrVT));
+ return DAG.getNode(Sequence, DL, MVT::Other, Chain, Dst, Src,
+ DAG.getConstant(Size, PtrVT));
+}
+
SDValue SystemZSelectionDAGInfo::
EmitTargetCodeForMemcpy(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
SDValue Dst, SDValue Src, SDValue Size, unsigned Align,
if (IsVolatile)
return SDValue();
- if (ConstantSDNode *CSize = dyn_cast<ConstantSDNode>(Size)) {
- uint64_t Bytes = CSize->getZExtValue();
- if (Bytes >= 1 && Bytes <= 0x100) {
- // A single MVC.
- return DAG.getNode(SystemZISD::MVC, DL, MVT::Other,
- Chain, Dst, Src, Size);
- }
- }
+ if (auto *CSize = dyn_cast<ConstantSDNode>(Size))
+ return emitMemMem(DAG, DL, SystemZISD::MVC, SystemZISD::MVC_LOOP,
+ Chain, Dst, Src, CSize->getZExtValue());
return SDValue();
}
SDValue Dst, SDValue Byte, SDValue Size,
unsigned Align, bool IsVolatile,
MachinePointerInfo DstPtrInfo) const {
- EVT DstVT = Dst.getValueType();
+ EVT PtrVT = Dst.getValueType();
if (IsVolatile)
return SDValue();
- if (ConstantSDNode *CSize = dyn_cast<ConstantSDNode>(Size)) {
+ if (auto *CSize = dyn_cast<ConstantSDNode>(Size)) {
uint64_t Bytes = CSize->getZExtValue();
if (Bytes == 0)
return SDValue();
- if (ConstantSDNode *CByte = dyn_cast<ConstantSDNode>(Byte)) {
+ if (auto *CByte = dyn_cast<ConstantSDNode>(Byte)) {
// Handle cases that can be done using at most two of
// MVI, MVHI, MVHHI and MVGHI. The latter two can only be
// used if ByteVal is all zeros or all ones; in other casees,
Align, DstPtrInfo);
if (Size2 == 0)
return Chain1;
- Dst = DAG.getNode(ISD::ADD, DL, DstVT, Dst,
- DAG.getConstant(Size1, DstVT));
+ Dst = DAG.getNode(ISD::ADD, DL, PtrVT, Dst,
+ DAG.getConstant(Size1, PtrVT));
DstPtrInfo = DstPtrInfo.getWithOffset(Size1);
SDValue Chain2 = memsetStore(DAG, DL, Chain, Dst, ByteVal, Size2,
std::min(Align, Size1), DstPtrInfo);
false, false, Align);
if (Bytes == 1)
return Chain1;
- SDValue Dst2 = DAG.getNode(ISD::ADD, DL, DstVT, Dst,
- DAG.getConstant(1, DstVT));
+ SDValue Dst2 = DAG.getNode(ISD::ADD, DL, PtrVT, Dst,
+ DAG.getConstant(1, PtrVT));
SDValue Chain2 = DAG.getStore(Chain, DL, Byte, Dst2,
DstPtrInfo.getWithOffset(1),
false, false, 1);
}
}
assert(Bytes >= 2 && "Should have dealt with 0- and 1-byte cases already");
- if (Bytes <= 0x101) {
- // Copy the byte to the first location and then use MVC to copy
- // it to the rest.
- Chain = DAG.getStore(Chain, DL, Byte, Dst, DstPtrInfo,
- false, false, Align);
- SDValue Dst2 = DAG.getNode(ISD::ADD, DL, DstVT, Dst,
- DAG.getConstant(1, DstVT));
- return DAG.getNode(SystemZISD::MVC, DL, MVT::Other, Chain, Dst2, Dst,
- DAG.getConstant(Bytes - 1, MVT::i32));
- }
+
+ // Handle the special case of a memset of 0, which can use XC.
+ auto *CByte = dyn_cast<ConstantSDNode>(Byte);
+ if (CByte && CByte->getZExtValue() == 0)
+ return emitMemMem(DAG, DL, SystemZISD::XC, SystemZISD::XC_LOOP,
+ Chain, Dst, Dst, Bytes);
+
+ // Copy the byte to the first location and then use MVC to copy
+ // it to the rest.
+ Chain = DAG.getStore(Chain, DL, Byte, Dst, DstPtrInfo,
+ false, false, Align);
+ SDValue DstPlus1 = DAG.getNode(ISD::ADD, DL, PtrVT, Dst,
+ DAG.getConstant(1, PtrVT));
+ return emitMemMem(DAG, DL, SystemZISD::MVC, SystemZISD::MVC_LOOP,
+ Chain, DstPlus1, Dst, Bytes - 1);
}
return SDValue();
}
+// Use CLC to compare [Src1, Src1 + Size) with [Src2, Src2 + Size),
+// deciding whether to use a loop or straight-line code.
+static SDValue emitCLC(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
+ SDValue Src1, SDValue Src2, uint64_t Size) {
+ SDVTList VTs = DAG.getVTList(MVT::Other, MVT::Glue);
+ EVT PtrVT = Src1.getValueType();
+ // A two-CLC sequence is a clear win over a loop, not least because it
+ // needs only one branch. A three-CLC sequence needs the same number
+ // of branches as a loop (i.e. 2), but is shorter. That brings us to
+ // lengths greater than 768 bytes. It seems relatively likely that
+ // a difference will be found within the first 768 bytes, so we just
+ // optimize for the smallest number of branch instructions, in order
+ // to avoid polluting the prediction buffer too much. A loop only ever
+ // needs 2 branches, whereas a straight-line sequence would need 3 or more.
+ if (Size > 3 * 256)
+ return DAG.getNode(SystemZISD::CLC_LOOP, DL, VTs, Chain, Src1, Src2,
+ DAG.getConstant(Size, PtrVT),
+ DAG.getConstant(Size / 256, PtrVT));
+ return DAG.getNode(SystemZISD::CLC, DL, VTs, Chain, Src1, Src2,
+ DAG.getConstant(Size, PtrVT));
+}
+
// Convert the current CC value into an integer that is 0 if CC == 0,
// less than zero if CC == 1 and greater than zero if CC >= 2.
// The sequence starts with IPM, which puts CC into bits 29 and 28
static SDValue addIPMSequence(SDLoc DL, SDValue Glue, SelectionDAG &DAG) {
SDValue IPM = DAG.getNode(SystemZISD::IPM, DL, MVT::i32, Glue);
SDValue SRL = DAG.getNode(ISD::SRL, DL, MVT::i32, IPM,
- DAG.getConstant(28, MVT::i32));
+ DAG.getConstant(SystemZ::IPM_CC, MVT::i32));
SDValue ROTL = DAG.getNode(ISD::ROTL, DL, MVT::i32, SRL,
DAG.getConstant(31, MVT::i32));
return ROTL;
SDValue Src1, SDValue Src2, SDValue Size,
MachinePointerInfo Op1PtrInfo,
MachinePointerInfo Op2PtrInfo) const {
- if (ConstantSDNode *CSize = dyn_cast<ConstantSDNode>(Size)) {
+ if (auto *CSize = dyn_cast<ConstantSDNode>(Size)) {
uint64_t Bytes = CSize->getZExtValue();
- if (Bytes >= 1 && Bytes <= 0x100) {
- // A single CLC.
- SDVTList VTs = DAG.getVTList(MVT::Other, MVT::Glue);
- Chain = DAG.getNode(SystemZISD::CLC, DL, VTs, Chain,
- Src1, Src2, Size);
- SDValue Glue = Chain.getValue(1);
- return std::make_pair(addIPMSequence(DL, Glue, DAG), Chain);
- }
+ assert(Bytes > 0 && "Caller should have handled 0-size case");
+ Chain = emitCLC(DAG, DL, Chain, Src1, Src2, Bytes);
+ SDValue Glue = Chain.getValue(1);
+ return std::make_pair(addIPMSequence(DL, Glue, DAG), Chain);
}
return std::make_pair(SDValue(), SDValue());
}
+std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::
+EmitTargetCodeForMemchr(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
+ SDValue Src, SDValue Char, SDValue Length,
+ MachinePointerInfo SrcPtrInfo) const {
+ // Use SRST to find the character. End is its address on success.
+ EVT PtrVT = Src.getValueType();
+ SDVTList VTs = DAG.getVTList(PtrVT, MVT::Other, MVT::Glue);
+ Length = DAG.getZExtOrTrunc(Length, DL, PtrVT);
+ Char = DAG.getZExtOrTrunc(Char, DL, MVT::i32);
+ Char = DAG.getNode(ISD::AND, DL, MVT::i32, Char,
+ DAG.getConstant(255, MVT::i32));
+ SDValue Limit = DAG.getNode(ISD::ADD, DL, PtrVT, Src, Length);
+ SDValue End = DAG.getNode(SystemZISD::SEARCH_STRING, DL, VTs, Chain,
+ Limit, Src, Char);
+ Chain = End.getValue(1);
+ SDValue Glue = End.getValue(2);
+
+ // Now select between End and null, depending on whether the character
+ // was found.
+ SmallVector<SDValue, 5> Ops;
+ Ops.push_back(End);
+ Ops.push_back(DAG.getConstant(0, PtrVT));
+ Ops.push_back(DAG.getConstant(SystemZ::CCMASK_SRST, MVT::i32));
+ Ops.push_back(DAG.getConstant(SystemZ::CCMASK_SRST_FOUND, MVT::i32));
+ Ops.push_back(Glue);
+ VTs = DAG.getVTList(PtrVT, MVT::Glue);
+ End = DAG.getNode(SystemZISD::SELECT_CCMASK, DL, VTs, Ops);
+ return std::make_pair(End, Chain);
+}
+
std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::
EmitTargetCodeForStrcpy(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
SDValue Dest, SDValue Src,
SDValue Glue = Chain.getValue(2);
return std::make_pair(addIPMSequence(DL, Glue, DAG), Chain);
}
+
+// Search from Src for a null character, stopping once Src reaches Limit.
+// Return a pair of values, the first being the number of nonnull characters
+// and the second being the out chain.
+//
+// This can be used for strlen by setting Limit to 0.
+static std::pair<SDValue, SDValue> getBoundedStrlen(SelectionDAG &DAG, SDLoc DL,
+ SDValue Chain, SDValue Src,
+ SDValue Limit) {
+ EVT PtrVT = Src.getValueType();
+ SDVTList VTs = DAG.getVTList(PtrVT, MVT::Other, MVT::Glue);
+ SDValue End = DAG.getNode(SystemZISD::SEARCH_STRING, DL, VTs, Chain,
+ Limit, Src, DAG.getConstant(0, MVT::i32));
+ Chain = End.getValue(1);
+ SDValue Len = DAG.getNode(ISD::SUB, DL, PtrVT, End, Src);
+ return std::make_pair(Len, Chain);
+}
+
+std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::
+EmitTargetCodeForStrlen(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
+ SDValue Src, MachinePointerInfo SrcPtrInfo) const {
+ EVT PtrVT = Src.getValueType();
+ return getBoundedStrlen(DAG, DL, Chain, Src, DAG.getConstant(0, PtrVT));
+}
+
+std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::
+EmitTargetCodeForStrnlen(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
+ SDValue Src, SDValue MaxLength,
+ MachinePointerInfo SrcPtrInfo) const {
+ EVT PtrVT = Src.getValueType();
+ MaxLength = DAG.getZExtOrTrunc(MaxLength, DL, PtrVT);
+ SDValue Limit = DAG.getNode(ISD::ADD, DL, PtrVT, Src, MaxLength);
+ return getBoundedStrlen(DAG, DL, Chain, Src, Limit);
+}
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