[llvm] [llvm][RISCV] Set ScalableVector stack id in proper place (PR #117862)

[Matt Arsenault via llvm-commits]

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@@ -1623,6 +1623,8 @@ bool RISCVFrameLowering::assignCalleeSavedSpillSlots(
     if ((unsigned)FrameIdx > MaxCSFrameIndex)
       MaxCSFrameIndex = FrameIdx;
     CS.setFrameIdx(FrameIdx);
+    if (RISCVRegisterInfo::isRVVRegClass(RC))
+      MFI.setStackID(FrameIdx, TargetStackID::ScalableVector);
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arsenm wrote:

The spill size is still an unsigned, and not a TypeSize. How do scalable types still have fixed spill sizes? 

https://github.com/llvm/llvm-project/pull/117862