[ARM] GlobalISel: Select globals in PIC mode
Support the selection of G_GLOBAL_VALUE in the PIC relocation model. For
simplicity we use the same pseudoinstructions for both Darwin and ELF:
(MOV|LDRLIT)_ga_pcrel(_ldr).
This is new for ELF, so it requires a small update to the ARM pseudo
expansion pass to make sure it adds the correct constant pool modifier
and add-current-address in the case of ELF.
Differential Revision: https://reviews.llvm.org/D36507
llvm-svn: 311992
diff --git a/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp b/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
index 1a5b7d2..18fd077 100644
--- a/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
+++ b/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
@@ -1308,9 +1308,11 @@
if (IsPIC) {
unsigned PCAdj = IsARM ? 8 : 4;
+ auto Modifier = STI->getCPModifier(GV);
ARMPCLabelIndex = AFI->createPICLabelUId();
- CPV = ARMConstantPoolConstant::Create(GV, ARMPCLabelIndex,
- ARMCP::CPValue, PCAdj);
+ CPV = ARMConstantPoolConstant::Create(
+ GV, ARMPCLabelIndex, ARMCP::CPValue, PCAdj, Modifier,
+ /*AddCurrentAddr*/ Modifier == ARMCP::GOT_PREL);
} else
CPV = ARMConstantPoolConstant::Create(GV, ARMCP::no_modifier);
diff --git a/llvm/lib/Target/ARM/ARMInstructionSelector.cpp b/llvm/lib/Target/ARM/ARMInstructionSelector.cpp
index 0d74fca..e2f9466 100644
--- a/llvm/lib/Target/ARM/ARMInstructionSelector.cpp
+++ b/llvm/lib/Target/ARM/ARMInstructionSelector.cpp
@@ -492,10 +492,6 @@
DEBUG(dbgs() << "ROPI and RWPI not supported yet\n");
return false;
}
- if (TM.isPositionIndependent()) {
- DEBUG(dbgs() << "PIC not supported yet\n");
- return false;
- }
auto GV = MIB->getOperand(1).getGlobal();
if (GV->isThreadLocal()) {
@@ -509,6 +505,28 @@
auto ObjectFormat = TII.getSubtarget().getTargetTriple().getObjectFormat();
bool UseMovt = TII.getSubtarget().useMovt(MF);
+ unsigned Alignment = 4;
+ if (TM.isPositionIndependent()) {
+ bool Indirect = TII.getSubtarget().isGVIndirectSymbol(GV);
+ // FIXME: Taking advantage of MOVT for ELF is pretty involved, so we don't
+ // support it yet. See PR28229.
+ unsigned Opc =
+ UseMovt && !TII.getSubtarget().isTargetELF()
+ ? (Indirect ? ARM::MOV_ga_pcrel_ldr : ARM::MOV_ga_pcrel)
+ : (Indirect ? ARM::LDRLIT_ga_pcrel_ldr : ARM::LDRLIT_ga_pcrel);
+ MIB->setDesc(TII.get(Opc));
+
+ if (TII.getSubtarget().isTargetDarwin())
+ MIB->getOperand(1).setTargetFlags(ARMII::MO_NONLAZY);
+
+ if (Indirect)
+ MIB.addMemOperand(MF.getMachineMemOperand(
+ MachinePointerInfo::getGOT(MF), MachineMemOperand::MOLoad,
+ TM.getPointerSize(), Alignment));
+
+ return true;
+ }
+
if (ObjectFormat == Triple::ELF) {
if (UseMovt) {
MIB->setDesc(TII.get(ARM::MOVi32imm));
@@ -516,7 +534,6 @@
// Load the global's address from the constant pool.
MIB->setDesc(TII.get(ARM::LDRi12));
MIB->RemoveOperand(1);
- unsigned Alignment = 4;
MIB.addConstantPoolIndex(
MF.getConstantPool()->getConstantPoolIndex(GV, Alignment),
/* Offset */ 0, /* TargetFlags */ 0)
diff --git a/llvm/lib/Target/ARM/ARMSubtarget.cpp b/llvm/lib/Target/ARM/ARMSubtarget.cpp
index 3a9f3c7..992d2a3 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.cpp
+++ b/llvm/lib/Target/ARM/ARMSubtarget.cpp
@@ -342,6 +342,13 @@
return false;
}
+ARMCP::ARMCPModifier ARMSubtarget::getCPModifier(const GlobalValue *GV) const {
+ if (isTargetELF() && TM.isPositionIndependent() &&
+ !TM.shouldAssumeDSOLocal(*GV->getParent(), GV))
+ return ARMCP::GOT_PREL;
+ return ARMCP::no_modifier;
+}
+
unsigned ARMSubtarget::getMispredictionPenalty() const {
return SchedModel.MispredictPenalty;
}
diff --git a/llvm/lib/Target/ARM/ARMSubtarget.h b/llvm/lib/Target/ARM/ARMSubtarget.h
index f9808f8..eb75ddc 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.h
+++ b/llvm/lib/Target/ARM/ARMSubtarget.h
@@ -16,6 +16,7 @@
#include "ARMBaseInstrInfo.h"
#include "ARMBaseRegisterInfo.h"
+#include "ARMConstantPoolValue.h"
#include "ARMFrameLowering.h"
#include "ARMISelLowering.h"
#include "ARMSelectionDAGInfo.h"
@@ -750,6 +751,9 @@
/// True if the GV will be accessed via an indirect symbol.
bool isGVIndirectSymbol(const GlobalValue *GV) const;
+ /// Returns the constant pool modifier needed to access the GV.
+ ARMCP::ARMCPModifier getCPModifier(const GlobalValue *GV) const;
+
/// True if fast-isel is used.
bool useFastISel() const;