[llvm-commits] [PATCH] TableGen CodeEmitter Backend for JITCodeEmitter

[Logan Chien]

Hi,

  I agree with you that pseudos are handled (and encoded) in
ARMCodeEmitter::emitPseudoInstruction.
But unfortunately, emitPseudoInstruction will try to call
CodeEmitter::getBinaryCodeForInstr first, then
getBinaryCodeForInstr will report a fatal error.  That's why I tried to add
new 'case' (though we are doing
nothing in getBinaryCodeForInstr.)  You may trace the control flow while
emitting LDMIA_RET or B,
and you will see why this patch is essential.  Thanks.

Sincerely,
Logan

On Fri, Jul 22, 2011 at 11:40 PM, Jim Grosbach <grosbach at apple.com> wrote:

> This isn't what you want to do. The reason pseudos are excluded is that
> they don't have any binary information to emit. Adding them to the
> getBinaryCodeForInstr() won't help, as it won't return any bits of the
> instruction anyway.
>
> Pseudos are handled in ARMCodeEmitter::emitPseudoInstruction(), and that
> function is required to fill in all required bits for the instruction(s) the
> pseudo expands to.
>
> -Jim
>
> On Jul 21, 2011, at 7:27 PM, Logan Chien wrote:
>
> Dear all,
>
>   With commit r134539, the CodeEmitter backend of TableGen will not
> generate case for
> pseudo instruction.  It seems that r134539 assumed that the pseudo
> instruction will
> be lowered before calling CodeEmitter::getBinaryCodeForInstr.  Thus,
> getBinaryCodeForInstr
> will report a fatal error if it gets a pseudo instruction.
>
>   However, ARMCodeEmitter does not lower the pseudo instruction before
> calling
> getBinaryCodeForInstr, and ARMCodeEmitter will no longer work after
> r134539.
> With this patch, we will generate case for pseudo instruction for
> CodeEmitter (but not
> MCCodeEmitter) just like what was done before.
>
>   Please review.  Thanks!
>
> Sincerely,
> Logan
> <0001-Fix-ARMCodeEmitter-pseudo-instruction-encoder.patch>
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