[PATCH] D70680: [ARM][Thumb2] Fix ADD/SUB invalid writes to SP

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


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Comment at: llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp:3285
       // we can handle a larger range of immediates.
+      const bool ToSP = DefMI.getOperand(0).getReg() == ARM::SP;
+      const unsigned t2ADD = ToSP ? ARM::t2ADDspImm : ARM::t2ADDri;
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dnsampaio wrote:
> efriedma wrote:
> > Do we need to care about the source register here?  t2ADDrr doesn't restrict it.  (I guess that might also be a bug?)
> From my tests, `rr` does block writing to `SP` and not reading from it:
> ```./llvm-mc --assemble  -triple=thumbv7-apple-darwin9 -mcpu=cortex-a9 --show-encoding <<< "add.w sp, r0, r1"
>         .section        __TEXT,__text,regular,pure_instructions
> <stdin>:1:7: error: source register must be sp if destination is sp
> add.w sp, r0, r1```
> 
> In that case, just checking that the destination is `SP` is enough.
We might need to split t2ADDrr eventually, but I guess this is fine for now.


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  https://reviews.llvm.org/D70680/new/

https://reviews.llvm.org/D70680