[llvm] r269969 - When looking for a spill slot in reg scavenger, find one that matches RC

[Jordy Potman via llvm-commits]

Hi Krzysztof,

I'm seeing an "Invalid Object Idx" assert in the call to
MFI.getObjectSize(FI) in the code below on my out of tree target after this
commit.

+    // Verify that this slot is valid for this register.
> +    int FI = Scavenged[I].FrameIndex;
> +    unsigned S = MFI.getObjectSize(FI);
> +    unsigned A = MFI.getObjectAlignment(FI);
> +    if (NeedSize > S || NeedAlign > A)
> +      continue;
>

The reason for this is that the Scavenged vector may contain a
ScavengedInfo structure with a FrameIndex of -1 after the first call of
scavengeRegister on targets where there is no spill slot but the target
knows how to save/restore the register (using TRI->saveScavengerRegister).
This ScavengedInfo structure with a FrameIndex of -1 is added to the
Scavenged vector by the code on lines 425-429 in the first call of
scavengeRegister.

I have fixed this in my tree by adding

if (FI < 0)
  continue;

before the the call to MFI.getObjectSize(FI) in the code above, see the
attached patch, but there may be a cleaner/better solution.

Jordy
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