Add an option to use a virtual register as the global base register instead of
reserving a physical register ($gp or $28) for that purpose.
This will completely eliminate loads that restore the value of $gp after every
function call, if the register allocator assigns a callee-saved register, or
eliminate unnecessary loads if it assigns a temporary register.
example:
.cpload $25 // set $gp.
...
.cprestore 16 // store $gp to stack slot 16($sp).
...
jalr $25 // function call. clobbers $gp.
lw $gp, 16($sp) // not emitted if callee-saved reg is chosen.
...
lw $2, 4($gp)
...
jalr $25 // function call.
lw $gp, 16($sp) // not emitted if $gp is not live after this instruction.
...
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151402 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/Mips/MipsISelLowering.cpp b/lib/Target/Mips/MipsISelLowering.cpp
index a93e0ac..968a78b 100644
--- a/lib/Target/Mips/MipsISelLowering.cpp
+++ b/lib/Target/Mips/MipsISelLowering.cpp
@@ -48,6 +48,11 @@
return true;
}
+static SDValue GetGlobalReg(SelectionDAG &DAG, EVT Ty) {
+ MipsFunctionInfo *FI = DAG.getMachineFunction().getInfo<MipsFunctionInfo>();
+ return DAG.getRegister(FI->getGlobalBaseReg(), Ty);
+}
+
const char *MipsTargetLowering::getTargetNodeName(unsigned Opcode) const {
switch (Opcode) {
case MipsISD::JmpLink: return "MipsISD::JmpLink";
@@ -1496,7 +1501,7 @@
(HasGotOfst ? MipsII::MO_GOT_PAGE : MipsII::MO_GOT_DISP) :
(HasGotOfst ? MipsII::MO_GOT : MipsII::MO_GOT16);
SDValue GA = DAG.getTargetGlobalAddress(GV, dl, ValTy, 0, GotFlag);
- GA = DAG.getNode(MipsISD::Wrapper, dl, ValTy, GA);
+ GA = DAG.getNode(MipsISD::Wrapper, dl, ValTy, GetGlobalReg(DAG, ValTy), GA);
SDValue ResNode = DAG.getLoad(ValTy, dl, DAG.getEntryNode(), GA,
MachinePointerInfo(), false, false, false, 0);
// On functions and global targets not internal linked only
@@ -1529,7 +1534,8 @@
unsigned GOTFlag = IsN64 ? MipsII::MO_GOT_PAGE : MipsII::MO_GOT;
unsigned OFSTFlag = IsN64 ? MipsII::MO_GOT_OFST : MipsII::MO_ABS_LO;
SDValue BAGOTOffset = DAG.getBlockAddress(BA, ValTy, true, GOTFlag);
- BAGOTOffset = DAG.getNode(MipsISD::Wrapper, dl, ValTy, BAGOTOffset);
+ BAGOTOffset = DAG.getNode(MipsISD::Wrapper, dl, ValTy,
+ GetGlobalReg(DAG, ValTy), BAGOTOffset);
SDValue BALOOffset = DAG.getBlockAddress(BA, ValTy, true, OFSTFlag);
SDValue Load = DAG.getLoad(ValTy, dl, DAG.getEntryNode(), BAGOTOffset,
MachinePointerInfo(), false, false, false, 0);
@@ -1554,7 +1560,8 @@
bool LocalDynamic = GV->hasInternalLinkage();
unsigned Flag = LocalDynamic ? MipsII::MO_TLSLDM :MipsII::MO_TLSGD;
SDValue TGA = DAG.getTargetGlobalAddress(GV, dl, PtrVT, 0, Flag);
- SDValue Argument = DAG.getNode(MipsISD::Wrapper, dl, PtrVT, TGA);
+ SDValue Argument = DAG.getNode(MipsISD::Wrapper, dl, PtrVT,
+ GetGlobalReg(DAG, PtrVT), TGA);
unsigned PtrSize = PtrVT.getSizeInBits();
IntegerType *PtrTy = Type::getIntNTy(*DAG.getContext(), PtrSize);
@@ -1591,7 +1598,8 @@
// Initial Exec TLS Model
SDValue TGA = DAG.getTargetGlobalAddress(GV, dl, PtrVT, 0,
MipsII::MO_GOTTPREL);
- TGA = DAG.getNode(MipsISD::Wrapper, dl, PtrVT, TGA);
+ TGA = DAG.getNode(MipsISD::Wrapper, dl, PtrVT, GetGlobalReg(DAG, PtrVT),
+ TGA);
Offset = DAG.getLoad(PtrVT, dl,
DAG.getEntryNode(), TGA, MachinePointerInfo(),
false, false, false, 0);
@@ -1628,7 +1636,8 @@
unsigned GOTFlag = IsN64 ? MipsII::MO_GOT_PAGE : MipsII::MO_GOT;
unsigned OfstFlag = IsN64 ? MipsII::MO_GOT_OFST : MipsII::MO_ABS_LO;
JTI = DAG.getTargetJumpTable(JT->getIndex(), PtrVT, GOTFlag);
- JTI = DAG.getNode(MipsISD::Wrapper, dl, PtrVT, JTI);
+ JTI = DAG.getNode(MipsISD::Wrapper, dl, PtrVT, GetGlobalReg(DAG, PtrVT),
+ JTI);
HiPart = DAG.getLoad(PtrVT, dl, DAG.getEntryNode(), JTI,
MachinePointerInfo(), false, false, false, 0);
JTILo = DAG.getTargetJumpTable(JT->getIndex(), PtrVT, OfstFlag);
@@ -1671,7 +1680,7 @@
unsigned OFSTFlag = IsN64 ? MipsII::MO_GOT_OFST : MipsII::MO_ABS_LO;
SDValue CP = DAG.getTargetConstantPool(C, ValTy, N->getAlignment(),
N->getOffset(), GOTFlag);
- CP = DAG.getNode(MipsISD::Wrapper, dl, ValTy, CP);
+ CP = DAG.getNode(MipsISD::Wrapper, dl, ValTy, GetGlobalReg(DAG, ValTy), CP);
SDValue Load = DAG.getLoad(ValTy, dl, DAG.getEntryNode(), CP,
MachinePointerInfo::getConstantPool(), false,
false, false, 0);
@@ -2210,7 +2219,7 @@
// If this is the first call, create a stack frame object that points to
// a location to which .cprestore saves $gp.
- if (IsO32 && IsPIC && !MipsFI->getGPFI())
+ if (IsO32 && IsPIC && MipsFI->globalBaseRegFixed() && !MipsFI->getGPFI())
MipsFI->setGPFI(MFI->CreateFixedObject(4, 0, true));
// Get the frame index of the stack frame object that points to the location
@@ -2384,7 +2393,8 @@
if (IsPICCall) {
if (GlobalOrExternal) {
// Load callee address
- Callee = DAG.getNode(MipsISD::Wrapper, dl, getPointerTy(), Callee);
+ Callee = DAG.getNode(MipsISD::Wrapper, dl, getPointerTy(),
+ GetGlobalReg(DAG, getPointerTy()), Callee);
SDValue LoadValue = DAG.getLoad(getPointerTy(), dl, DAG.getEntryNode(),
Callee, MachinePointerInfo::getGOT(),
false, false, false, 0);