[llvm-commits] CVS: llvm/lib/Target/X86/X86RegisterInfo.cpp

[Chris Lattner]

On Tue, 13 Jun 2006, Chris Lattner wrote:
> Does this fix PR331?

Actually no, I don't think it does.  Dynamic alloca lowering would also 
need to be updated.  That would be a logical next step :)

-Chris

> -Chris
>
> On Tue, 13 Jun 2006, Evan Cheng wrote:
>
>> 
>> 
>> Changes in directory llvm/lib/Target/X86:
>> 
>> X86RegisterInfo.cpp updated: 1.157 -> 1.158
>> ---
>> Log message:
>> 
>> Cygwin support: use _alloca to allocate stack if > 4k. Patch by Anton 
>> Korobeynikov.
>> 
>> ---
>> Diffs of the changes:  (+21 -4)
>> 
>> X86RegisterInfo.cpp |   25 +++++++++++++++++++++----
>> 1 files changed, 21 insertions(+), 4 deletions(-)
>> 
>> 
>> Index: llvm/lib/Target/X86/X86RegisterInfo.cpp
>> diff -u llvm/lib/Target/X86/X86RegisterInfo.cpp:1.157 
>> llvm/lib/Target/X86/X86RegisterInfo.cpp:1.158
>> --- llvm/lib/Target/X86/X86RegisterInfo.cpp:1.157	Tue Jun  6 18:30:24 
>> 2006
>> +++ llvm/lib/Target/X86/X86RegisterInfo.cpp	Tue Jun 13 00:14:44 2006
>> @@ -740,7 +740,7 @@
>>   const Function* Fn = MF.getFunction();
>>   const X86Subtarget* Subtarget = 
>> &MF.getTarget().getSubtarget<X86Subtarget>();
>>   MachineInstr *MI;
>> -
>> +
>>   // Get the number of bytes to allocate from the FrameInfo
>>   unsigned NumBytes = MFI->getStackSize();
>>   if (MFI->hasCalls() || MF.getFrameInfo()->hasVarSizedObjects()) {
>> @@ -760,9 +760,20 @@
>>   MFI->setStackSize(NumBytes);
>> 
>>   if (NumBytes) {   // adjust stack pointer: ESP -= numbytes
>> -    unsigned Opc = NumBytes < 128 ? X86::SUB32ri8 : X86::SUB32ri;
>> -    MI = BuildMI(Opc, 1, 
>> X86::ESP,MachineOperand::UseAndDef).addImm(NumBytes);
>> -    MBB.insert(MBBI, MI);
>> +    if (NumBytes >= 4096 && Subtarget->TargetType == 
>> X86Subtarget::isCygwin) {
>> +      // Function prologue calls _alloca to probe the stack when 
>> allocating
>> +      // more than 4k bytes in one go. Touching the stack at 4K increments 
>> is
>> +      // necessary to ensure that the guard pages used by the OS virtual 
>> memory
>> +      // manager are allocated in correct sequence.
>> +      MI = BuildMI(X86::MOV32ri, 2, X86::EAX).addImm(NumBytes);
>> +      MBB.insert(MBBI, MI);
>> +      MI = BuildMI(X86::CALLpcrel32, 1).addExternalSymbol("_alloca");
>> +      MBB.insert(MBBI, MI);
>> +    } else {
>> +      unsigned Opc = NumBytes < 128 ? X86::SUB32ri8 : X86::SUB32ri;
>> +      MI = BuildMI(Opc, 1, 
>> X86::ESP,MachineOperand::UseAndDef).addImm(NumBytes);
>> +      MBB.insert(MBBI, MI);
>> +    }
>>   }
>> 
>>   if (hasFP(MF)) {
>> @@ -789,6 +800,12 @@
>>       Subtarget->TargetType == X86Subtarget::isCygwin) {
>>     MI = BuildMI(X86::AND32ri, 2, X86::ESP).addImm(-Align);
>>     MBB.insert(MBBI, MI);
>> +
>> +    // Probe the stack
>> +    MI = BuildMI(X86::MOV32ri, 2, X86::EAX).addImm(Align);
>> +    MBB.insert(MBBI, MI);
>> +    MI = BuildMI(X86::CALLpcrel32, 1).addExternalSymbol("_alloca");
>> +    MBB.insert(MBBI, MI);
>>   }
>> }
>> 
>> 
>> 
>> 
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>> 
>
> -Chris
>
>

-Chris

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