Move the code for initializing the global base reg out of
X86ISelDAGToDAG.cpp and into X86InstrInfo.cpp. This will allow
it to be reused by FastISel.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56494 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp
index 4c597ed..0864fa0 100644
--- a/lib/Target/X86/X86InstrInfo.cpp
+++ b/lib/Target/X86/X86InstrInfo.cpp
@@ -2935,3 +2935,32 @@
}
return Size;
}
+
+/// initializeGlobalBaseReg - Output the instructions required to put the
+/// base address to use for accessing globals into a register.
+///
+unsigned X86InstrInfo::initializeGlobalBaseReg(MachineFunction *MF) const {
+ // Insert the set of GlobalBaseReg into the first MBB of the function
+ MachineBasicBlock &FirstMBB = MF->front();
+ MachineBasicBlock::iterator MBBI = FirstMBB.begin();
+ MachineRegisterInfo &RegInfo = MF->getRegInfo();
+ unsigned PC = RegInfo.createVirtualRegister(X86::GR32RegisterClass);
+
+ const TargetInstrInfo *TII = TM.getInstrInfo();
+ // Operand of MovePCtoStack is completely ignored by asm printer. It's
+ // only used in JIT code emission as displacement to pc.
+ BuildMI(FirstMBB, MBBI, TII->get(X86::MOVPC32r), PC).addImm(0);
+
+ // If we're using vanilla 'GOT' PIC style, we should use relative addressing
+ // not to pc, but to _GLOBAL_ADDRESS_TABLE_ external
+ if (TM.getRelocationModel() == Reloc::PIC_ &&
+ TM.getSubtarget<X86Subtarget>().isPICStyleGOT()) {
+ unsigned GlobalBaseReg =
+ RegInfo.createVirtualRegister(X86::GR32RegisterClass);
+ BuildMI(FirstMBB, MBBI, TII->get(X86::ADD32ri), GlobalBaseReg)
+ .addReg(PC).addExternalSymbol("_GLOBAL_OFFSET_TABLE_");
+ return GlobalBaseReg;
+ }
+
+ return PC;
+}