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-rw-r--r--lib/Target/ARM/ARMBaseRegisterInfo.cpp99
-rw-r--r--lib/Target/ARM/ARMBaseRegisterInfo.h6
-rw-r--r--lib/Target/ARM/Thumb1RegisterInfo.cpp16
3 files changed, 95 insertions, 26 deletions
diff --git a/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index 8c1b913a20..be33ed6427 100644
--- a/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -50,6 +50,10 @@ EnableLocalStackAlloc("enable-local-stack-alloc", cl::init(true), cl::Hidden,
using namespace llvm;
+static cl::opt<bool>
+EnableBasePointer("arm-use-base-pointer", cl::Hidden, cl::init(true),
+ cl::desc("Enable use of a base pointer for complex stack frames"));
+
unsigned ARMBaseRegisterInfo::getRegisterNumbering(unsigned RegEnum,
bool *isSPVFP) {
if (isSPVFP)
@@ -146,7 +150,8 @@ ARMBaseRegisterInfo::ARMBaseRegisterInfo(const ARMBaseInstrInfo &tii,
const ARMSubtarget &sti)
: ARMGenRegisterInfo(ARM::ADJCALLSTACKDOWN, ARM::ADJCALLSTACKUP),
TII(tii), STI(sti),
- FramePtr((STI.isTargetDarwin() || STI.isThumb()) ? ARM::R7 : ARM::R11) {
+ FramePtr((STI.isTargetDarwin() || STI.isThumb()) ? ARM::R7 : ARM::R11),
+ BasePtr(ARM::R6) {
}
const unsigned*
@@ -182,6 +187,8 @@ getReservedRegs(const MachineFunction &MF) const {
Reserved.set(ARM::FPSCR);
if (hasFP(MF))
Reserved.set(FramePtr);
+ if (hasBasePointer(MF))
+ Reserved.set(BasePtr);
// Some targets reserve R9.
if (STI.isR9Reserved())
Reserved.set(ARM::R9);
@@ -195,6 +202,10 @@ bool ARMBaseRegisterInfo::isReservedReg(const MachineFunction &MF,
case ARM::SP:
case ARM::PC:
return true;
+ case ARM::R6:
+ if (hasBasePointer(MF))
+ return true;
+ break;
case ARM::R7:
case ARM::R11:
if (FramePtr == Reg && hasFP(MF))
@@ -625,35 +636,49 @@ bool ARMBaseRegisterInfo::hasFP(const MachineFunction &MF) const {
MFI->isFrameAddressTaken());
}
-bool ARMBaseRegisterInfo::canRealignStack(const MachineFunction &MF) const {
+bool ARMBaseRegisterInfo::hasBasePointer(const MachineFunction &MF) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
- return (RealignStack &&
- !AFI->isThumb1OnlyFunction() &&
- !MFI->hasVarSizedObjects());
+
+ if (!EnableBasePointer)
+ return false;
+
+ if (needsStackRealignment(MF) && MFI->hasVarSizedObjects())
+ return true;
+
+ // Thumb has trouble with negative offsets from the FP. Thumb2 has a limited
+ // negative range for ldr/str (255), and thumb1 is positive offsets only.
+ // It's going to be better to use the SP or Base Pointer instead. When there
+ // are variable sized objects, we can't reference off of the SP, so we
+ // reserve a Base Pointer.
+ if (AFI->isThumbFunction() && MFI->hasVarSizedObjects()) {
+ // Conservatively estimate whether the negative offset from the frame
+ // pointer will be sufficient to reach. If a function has a smallish
+ // frame, it's less likely to have lots of spills and callee saved
+ // space, so it's all more likely to be within range of the frame pointer.
+ // If it's wrong, the scavenger will still enable access to work, it just
+ // won't be optimal.
+ if (AFI->isThumb2Function() && MFI->getLocalFrameSize() < 128)
+ return false;
+ return true;
+ }
+
+ return false;
+}
+
+bool ARMBaseRegisterInfo::canRealignStack(const MachineFunction &MF) const {
+ const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
+ return (RealignStack && !AFI->isThumb1OnlyFunction());
}
bool ARMBaseRegisterInfo::
needsStackRealignment(const MachineFunction &MF) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
const Function *F = MF.getFunction();
- const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
unsigned StackAlign = MF.getTarget().getFrameInfo()->getStackAlignment();
bool requiresRealignment = ((MFI->getLocalFrameMaxAlign() > StackAlign) ||
F->hasFnAttr(Attribute::StackAlignment));
- // FIXME: Currently we don't support stack realignment for functions with
- // variable-sized allocas.
- // FIXME: It's more complicated than this...
- if (0 && requiresRealignment && MFI->hasVarSizedObjects())
- report_fatal_error(
- "Stack realignment in presense of dynamic allocas is not supported");
-
- // FIXME: This probably isn't the right place for this.
- if (0 && requiresRealignment && AFI->isThumb1OnlyFunction())
- report_fatal_error(
- "Stack realignment in thumb1 functions is not supported");
-
return requiresRealignment && canRealignStack(MF);
}
@@ -776,6 +801,10 @@ ARMBaseRegisterInfo::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
if (AFI->isThumb1OnlyFunction() && AFI->getVarArgsRegSaveSize() > 0)
MF.getRegInfo().setPhysRegUsed(ARM::LR);
+ // Spill the BasePtr if it's used.
+ if (hasBasePointer(MF))
+ MF.getRegInfo().setPhysRegUsed(BasePtr);
+
// Don't spill FP if the frame can be eliminated. This is determined
// by scanning the callee-save registers to see if any is used.
const unsigned *CSRegs = getCalleeSavedRegs();
@@ -1022,13 +1051,14 @@ ARMBaseRegisterInfo::ResolveFrameIndexReference(const MachineFunction &MF,
return Offset - AFI->getDPRCalleeSavedAreaOffset();
// When dynamically realigning the stack, use the frame pointer for
- // parameters, and the stack pointer for locals.
+ // parameters, and the stack/base pointer for locals.
if (needsStackRealignment(MF)) {
assert (hasFP(MF) && "dynamic stack realignment without a FP!");
if (isFixed) {
FrameReg = getFrameRegister(MF);
Offset = FPOffset;
- }
+ } else if (MFI->hasVarSizedObjects())
+ FrameReg = BasePtr;
return Offset;
}
@@ -1036,9 +1066,13 @@ ARMBaseRegisterInfo::ResolveFrameIndexReference(const MachineFunction &MF,
if (hasFP(MF) && AFI->hasStackFrame()) {
// Use frame pointer to reference fixed objects. Use it for locals if
// there are VLAs (and thus the SP isn't reliable as a base).
- if (isFixed || MFI->hasVarSizedObjects()) {
+ if (isFixed || (MFI->hasVarSizedObjects() && !hasBasePointer(MF))) {
FrameReg = getFrameRegister(MF);
Offset = FPOffset;
+ } else if (MFI->hasVarSizedObjects()) {
+ assert(hasBasePointer(MF) && "missing base pointer!");
+ // Use the base register since we have it.
+ FrameReg = BasePtr;
} else if (AFI->isThumb2Function()) {
// In Thumb2 mode, the negative offset is very limited. Try to avoid
// out of range references.
@@ -1052,6 +1086,9 @@ ARMBaseRegisterInfo::ResolveFrameIndexReference(const MachineFunction &MF,
Offset = FPOffset;
}
}
+ // Use the base pointer if we have one.
+ if (hasBasePointer(MF))
+ FrameReg = BasePtr;
return Offset;
}
@@ -1089,7 +1126,8 @@ unsigned ARMBaseRegisterInfo::getRegisterPairEven(unsigned Reg,
case ARM::R5:
return ARM::R4;
case ARM::R7:
- return isReservedReg(MF, ARM::R7) ? 0 : ARM::R6;
+ return (isReservedReg(MF, ARM::R7) || isReservedReg(MF, ARM::R6))
+ ? 0 : ARM::R6;
case ARM::R9:
return isReservedReg(MF, ARM::R9) ? 0 :ARM::R8;
case ARM::R11:
@@ -1178,7 +1216,8 @@ unsigned ARMBaseRegisterInfo::getRegisterPairOdd(unsigned Reg,
case ARM::R4:
return ARM::R5;
case ARM::R6:
- return isReservedReg(MF, ARM::R7) ? 0 : ARM::R7;
+ return (isReservedReg(MF, ARM::R7) || isReservedReg(MF, ARM::R6))
+ ? 0 : ARM::R7;
case ARM::R8:
return isReservedReg(MF, ARM::R9) ? 0 :ARM::R9;
case ARM::R10:
@@ -1878,6 +1917,20 @@ emitPrologue(MachineFunction &MF) const {
AFI->setShouldRestoreSPFromFP(true);
}
+ // If we need a base pointer, set it up here. It's whatever the value
+ // of the stack pointer is at this point. Any variable size objects
+ // will be allocated after this, so we can still use the base pointer
+ // to reference locals.
+ if (hasBasePointer(MF)) {
+ if (isARM)
+ BuildMI(MBB, MBBI, dl, TII.get(ARM::MOVr), BasePtr)
+ .addReg(ARM::SP)
+ .addImm((unsigned)ARMCC::AL).addReg(0).addReg(0);
+ else
+ BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVgpr2gpr), BasePtr)
+ .addReg(ARM::SP);
+ }
+
// If the frame has variable sized objects then the epilogue must restore
// the sp from fp.
if (!AFI->shouldRestoreSPFromFP() && MFI->hasVarSizedObjects())
diff --git a/lib/Target/ARM/ARMBaseRegisterInfo.h b/lib/Target/ARM/ARMBaseRegisterInfo.h
index c814f998d5..fa2eb6c104 100644
--- a/lib/Target/ARM/ARMBaseRegisterInfo.h
+++ b/lib/Target/ARM/ARMBaseRegisterInfo.h
@@ -52,6 +52,11 @@ protected:
/// FramePtr - ARM physical register used as frame ptr.
unsigned FramePtr;
+ /// BasePtr - ARM physical register used as a base ptr in complex stack
+ /// frames. I.e., when we need a 3rd base, not just SP and FP, due to
+ /// variable size stack objects.
+ unsigned BasePtr;
+
// Can be only subclassed.
explicit ARMBaseRegisterInfo(const ARMBaseInstrInfo &tii,
const ARMSubtarget &STI);
@@ -102,6 +107,7 @@ public:
MachineFunction &MF) const;
bool hasFP(const MachineFunction &MF) const;
+ bool hasBasePointer(const MachineFunction &MF) const;
bool canRealignStack(const MachineFunction &MF) const;
bool needsStackRealignment(const MachineFunction &MF) const;
diff --git a/lib/Target/ARM/Thumb1RegisterInfo.cpp b/lib/Target/ARM/Thumb1RegisterInfo.cpp
index c562c37146..a21a3da10b 100644
--- a/lib/Target/ARM/Thumb1RegisterInfo.cpp
+++ b/lib/Target/ARM/Thumb1RegisterInfo.cpp
@@ -604,9 +604,12 @@ Thumb1RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
else if (MF.getFrameInfo()->hasVarSizedObjects()) {
assert(SPAdj == 0 && hasFP(MF) && "Unexpected");
// There are alloca()'s in this function, must reference off the frame
- // pointer instead.
- FrameReg = getFrameRegister(MF);
- Offset -= AFI->getFramePtrSpillOffset();
+ // pointer or base pointer instead.
+ if (!hasBasePointer(MF)) {
+ FrameReg = getFrameRegister(MF);
+ Offset -= AFI->getFramePtrSpillOffset();
+ } else
+ FrameReg = BasePtr;
}
// Special handling of dbg_value instructions.
@@ -787,6 +790,13 @@ void Thumb1RegisterInfo::emitPrologue(MachineFunction &MF) const {
AFI->setGPRCalleeSavedArea1Size(GPRCS1Size);
AFI->setGPRCalleeSavedArea2Size(GPRCS2Size);
AFI->setDPRCalleeSavedAreaSize(DPRCSSize);
+
+ // If we need a base pointer, set it up here. It's whatever the value
+ // of the stack pointer is at this point. Any variable size objects
+ // will be allocated after this, so we can still use the base pointer
+ // to reference locals.
+ if (hasBasePointer(MF))
+ BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVgpr2gpr), BasePtr).addReg(ARM::SP);
}
static bool isCalleeSavedRegister(unsigned Reg, const unsigned *CSRegs) {
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2025-05-21 17:53:44 +0000