[PATCH] D95586: [ARM] permit PC as destination of MOVS

[Nick Desaulniers via Phabricator via llvm-commits]

nickdesaulniers added a comment.

In D95586#2549706 <https://reviews.llvm.org/D95586#2549706>, @nickdesaulniers wrote:

> ACK
>
> It looks like the kernel also uses
>
>   movs pc, lr
>
> for thumb2 kernel images. Maybe I should repurpose this review for supporting `pc` operand in thumb? `llvm/test/MC/ARM/thumb-mov.s`/`llvm/test/MC/ARM/lsl-zero-errors.s`, or create a new review?

err, is there a way to express that an inst alias should pass a literal `0`?

  diff --git a/llvm/lib/Target/ARM/ARMInstrThumb2.td b/llvm/lib/Target/ARM/ARMInstrThumb2.td
  index 5642cab32e7c..82f9096957eb 100644
  --- a/llvm/lib/Target/ARM/ARMInstrThumb2.td
  +++ b/llvm/lib/Target/ARM/ARMInstrThumb2.td
  @@ -4144,6 +4144,7 @@ def t2SUBS_PC_LR : T2I <(outs), (ins imm0_255:$imm), NoItinerary,
     bits<8> imm;
     let Inst{7-0} = imm;
   }
  +def : t2InstAlias<"movs pc, lr", (t2SUBS_PC_LR imm0_255:"0")>;
   
   // Hypervisor Call is a system instruction.
   let isCall = 1 in {



  llvm-project/llvm/lib/Target/ARM/ARMInstrThumb2.td:4147:57: error: expected variable name in dag literal
  def : t2InstAlias<"movs pc, lr", (t2SUBS_PC_LR imm0_255:"0")>;
                                                          ^

???


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