[llvm-commits] [llvm] r83136 - /llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp

[Evan Cheng]

On Sep 29, 2009, at 6:43 PM, Jim Grosbach wrote:

>
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> ======================================================================
> --- llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp (original)
> +++ llvm/trunk/lib/Target/ARM/ARMBaseRegisterInfo.cpp Tue Sep 29  
> 20:43:29 2009
> @@ -654,7 +654,13 @@
>     // adjustments also, even when the frame itself is small.
>     if (RS && !ExtraCSSpill) {
>       MachineFrameInfo  *MFI = MF.getFrameInfo();
> -      if (estimateStackSize(MF, MFI) >= estimateRSStackSizeLimit(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 previous FP.
> +      if (estimateStackSize(MF, MFI) + (hasFP(MF) ? 4 : 0)
> +          >= estimateRSStackSizeLimit(MF)

In processFunctionBeforeCalleeSavedScan:

     // Darwin ABI requires FP to point to the stack slot that  
contains the
     // previous FP.
     if (STI.isTargetDarwin() || hasFP(MF)) {
       MF.getRegInfo().setPhysRegUsed(FramePtr);
       NumGPRSpills++;
     }

So if it's Darwin it spills fp even if hasFP is false (unless the  
function is frameless). Also FP points to the slot that contains  
previous FP. It's not "FP points to the previous FP". Is the  
adjustment 4 always right?

Evan


>           || AFI->isThumb1OnlyFunction()) {
>         // If any non-reserved CS register isn't spilled, just spill  
> one or two
>         // extra. That should take care of it!
>
>
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