Commit 910d7123 authored by Tom Stellard's avatar Tom Stellard
Browse files

Merging r262577: 

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r262577 | thomas.stellard | 2016-03-02 19:45:09 -0800 (Wed, 02 Mar 2016) | 12 lines

AMDGPU/SI: Don't try to move scratch wave offset when there are no free SGPRs

Summary:
When there were no free SGPRs, we were trying to move this value into
some of the reserved registers which was causing a segmentation fault.

Reviewers: arsenm

Subscribers: arsenm, llvm-commits

Differential Revision: http://reviews.llvm.org/D17590

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llvm-svn: 271720
parent d909615c

llvm/lib/Target/AMDGPU/SIFrameLowering.cpp

+15 −3
Original line number Diff line number Diff line
@@ -165,10 +165,22 @@ void SIFrameLowering::emitPrologue(MachineFunction &MF, 


    if (ScratchWaveOffsetReg == TRI->reservedPrivateSegmentWaveByteOffsetReg(MF)) {

      MachineRegisterInfo &MRI = MF.getRegInfo();

      // Skip the last 2 elements because the last one is reserved for VCC, and

      // this is the 2nd to last element already.

      unsigned NumPreloaded = MFI->getNumPreloadedSGPRs();

      for (MCPhysReg Reg : getAllSGPRs().drop_back(6).slice(NumPreloaded)) {



      // We need to drop register from the end of the list that we cannot use

      // for the scratch wave offset.

      // + 2 s102 and s103 do not exist on VI.

      // + 2 for vcc

      // + 2 for xnack_mask

      // + 2 for flat_scratch

      // + 4 for registers reserved for scratch resource register

      // + 1 for register reserved for scratch wave offset.  (By exluding this

      //     register from the list to consider, it means that when this

      //     register is being used for the scratch wave offset and there

      //     are no other free SGPRs, then the value will stay in this register.

      // ----

      //  13

      for (MCPhysReg Reg : getAllSGPRs().drop_back(13).slice(NumPreloaded)) {

        // Pick the first unallocated SGPR. Be careful not to pick an alias of the

        // scratch descriptor, since we haven’t added its uses yet.

        if (!MRI.isPhysRegUsed(Reg)) {