[PATCH] D135693: [WIP][RegisterScavenger][RISCV] Don't search for FrameSetup instrs if we were searching from Non-FrameSetup instrs

[Craig Topper via Phabricator via llvm-commits]

craig.topper added a comment.

In D135693#3850055 <https://reviews.llvm.org/D135693#3850055>, @craig.topper wrote:

> If I understand correctly, the use of a vreg in the frame-setup allowed findSurvivorBackward to trigger this code
>
>   // Keep searching when we find a vreg since the spilled register will
>   // be usefull for this other vreg as well later.
>   bool FoundVReg = false;
>   for (const MachineOperand &MO : MI.operands()) {
>     if (MO.isReg() && Register::isVirtualRegister(MO.getReg())) {
>       FoundVReg = true;
>       break;
>     }
>   }
>   if (FoundVReg) {
>     InstrCountDown = InstrLimit;
>     Pos = I;
>   }
>
> which caused the search to stop above the frame-setup. So another option might be to use T1 as the scratch register in frame-setup as was once proposed in an earlier revision of https://reviews.llvm.org/D61884

But we can't use T1 with shrink wrapping and I've confirmed the same bug exists with shrink wrapping.


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https://reviews.llvm.org/D135693