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Create a stack frame on ARM when

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- Function uses all scratch registers AND
- Function does not use any callee saved registers AND
- Stack size is too big to address with immediate offsets.

In this case a register must be scavenged to calculate the address of a stack
object, and the scavenger needs a spare register or emergency spill slot.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97071 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2010-02-24 22:43:17 +00:00
parent 9792de7363
commit 657baec0af
2 changed files with 56 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

82
lib/Target/ARM/ARMBaseRegisterInfo.cpp
View File

@ -513,7 +513,7 @@ cannotEliminateFrame(const MachineFunction &MF) const {
}
/// estimateStackSize - Estimate and return the size of the frame.
static unsigned estimateStackSize(MachineFunction &MF, MachineFrameInfo *MFI) {
static unsigned estimateStackSize(MachineFunction &MF) {
const MachineFrameInfo *FFI = MF.getFrameInfo();
int Offset = 0;
for (int i = FFI->getObjectIndexBegin(); i != 0; ++i) {
@ -671,8 +671,16 @@ ARMBaseRegisterInfo::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
}
}
// If any of the stack slot references may be out of range of an immediate
// offset, make sure a register (or a spill slot) is available for the
// register scavenger. Note that if we're indexing off the frame pointer, the
// effective stack size is 4 bytes larger since the FP points to the stack
// slot of the previous FP.
bool BigStack = RS &&
estimateStackSize(MF) + (hasFP(MF) ? 4 : 0) >= estimateRSStackSizeLimit(MF);
bool ExtraCSSpill = false;
if (!CanEliminateFrame || cannotEliminateFrame(MF)) {
if (BigStack || !CanEliminateFrame || cannotEliminateFrame(MF)) {
AFI->setHasStackFrame(true);
// If LR is not spilled, but at least one of R4, R5, R6, and R7 is spilled.
@ -727,51 +735,43 @@ ARMBaseRegisterInfo::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
// callee-saved register or reserve a special spill slot to facilitate
// register scavenging. Thumb1 needs a spill slot for stack pointer
// adjustments also, even when the frame itself is small.
if (RS && !ExtraCSSpill) {
MachineFrameInfo *MFI = MF.getFrameInfo();
// If any of the stack slot references may be out of range of an
// immediate offset, make sure a register (or a spill slot) is
// available for the register scavenger. Note that if we're indexing
// off the frame pointer, the effective stack size is 4 bytes larger
// since the FP points to the stack slot of the previous FP.
if (estimateStackSize(MF, MFI) + (hasFP(MF) ? 4 : 0)
>= estimateRSStackSizeLimit(MF)) {
// If any non-reserved CS register isn't spilled, just spill one or two
// extra. That should take care of it!
unsigned NumExtras = TargetAlign / 4;
SmallVector<unsigned, 2> Extras;
while (NumExtras && !UnspilledCS1GPRs.empty()) {
unsigned Reg = UnspilledCS1GPRs.back();
UnspilledCS1GPRs.pop_back();
if (BigStack && !ExtraCSSpill) {
// If any non-reserved CS register isn't spilled, just spill one or two
// extra. That should take care of it!
unsigned NumExtras = TargetAlign / 4;
SmallVector<unsigned, 2> Extras;
while (NumExtras && !UnspilledCS1GPRs.empty()) {
unsigned Reg = UnspilledCS1GPRs.back();
UnspilledCS1GPRs.pop_back();
if (!isReservedReg(MF, Reg)) {
Extras.push_back(Reg);
NumExtras--;
}
}
// For non-Thumb1 functions, also check for hi-reg CS registers
if (!AFI->isThumb1OnlyFunction()) {
while (NumExtras && !UnspilledCS2GPRs.empty()) {
unsigned Reg = UnspilledCS2GPRs.back();
UnspilledCS2GPRs.pop_back();
if (!isReservedReg(MF, Reg)) {
Extras.push_back(Reg);
NumExtras--;
}
}
// For non-Thumb1 functions, also check for hi-reg CS registers
if (!AFI->isThumb1OnlyFunction()) {
while (NumExtras && !UnspilledCS2GPRs.empty()) {
unsigned Reg = UnspilledCS2GPRs.back();
UnspilledCS2GPRs.pop_back();
if (!isReservedReg(MF, Reg)) {
Extras.push_back(Reg);
NumExtras--;
}
}
}
if (Extras.size() && NumExtras == 0) {
for (unsigned i = 0, e = Extras.size(); i != e; ++i) {
MF.getRegInfo().setPhysRegUsed(Extras[i]);
AFI->setCSRegisterIsSpilled(Extras[i]);
}
} else if (!AFI->isThumb1OnlyFunction()) {
// note: Thumb1 functions spill to R12, not the stack.
// Reserve a slot closest to SP or frame pointer.
const TargetRegisterClass *RC = ARM::GPRRegisterClass;
RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
RC->getAlignment(),
false));
}
if (Extras.size() && NumExtras == 0) {
for (unsigned i = 0, e = Extras.size(); i != e; ++i) {
MF.getRegInfo().setPhysRegUsed(Extras[i]);
AFI->setCSRegisterIsSpilled(Extras[i]);
}
} else if (!AFI->isThumb1OnlyFunction()) {
// note: Thumb1 functions spill to R12, not the stack. Reserve a slot
// closest to SP or frame pointer.
const TargetRegisterClass *RC = ARM::GPRRegisterClass;
MachineFrameInfo *MFI = MF.getFrameInfo();
RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
RC->getAlignment(),
false));
}
}
}

15
test/CodeGen/Thumb2/2010-02-24-BigStack.ll Normal file
View File

@ -0,0 +1,15 @@
; RUN: llc < %s -O0 -relocation-model=pic -disable-fp-elim -mcpu=cortex-a8 -mattr=+vfp2
; This test creates a big stack frame without spilling any callee-saved registers.
; Make sure the whole stack frame is addrerssable wiothout scavenger crashes.
target datalayout = "e-p:32:32:32-i1:8:32-i8:8:32-i16:16:32-i32:32:32-i64:32:32-f32:32:32-f64:32:32-v64:64:64-v128:128:128-a0:0:32-n32"
target triple = "thumbv7-apple-darwin3.0.0-iphoneos"
define arm_apcscc void @FindMin(double* %panelTDEL, i8* %dclOfRow, i32 %numRows, i32 %numCols, double* %retMin_RES_TDEL) {
entry:
%panelTDEL.addr = alloca double*, align 4 ; <double**> [#uses=1]
%panelResTDEL = alloca [2560 x double], align 4 ; <[2560 x double]*> [#uses=0]
store double* %panelTDEL, double** %panelTDEL.addr
store double* %retMin_RES_TDEL, double** undef
store i32 0, i32* undef
unreachable
}