Re: [PATCH] Add reg_truncated_to_mode to rtl_hooks

[Paolo Bonzini <paolo dot bonzini at lu dot unisi dot ch>]

Adam Nemet wrote:
> This patch adds reg_truncated_to_mode to rtl_hooks.  With this we can
> now turn TRUNCATEs into SUBREGs in simplify_unary_operation_1.  The
> patch is similar to the respective part of Paolo Bonzini's patch from
> http://gcc.gnu.org/ml/gcc-patches/2006-02/msg00684.html.

Even though I cannot approve it, thank you very much for tackling this.

> With these changes we remove seven truncations in
> gcc.c-torture/execute.  They all seem to have been unnecessary.

All for the better.

> + /* Suppose that truncation from the machine mode of X to MODE is not a
> +    no-op.  See if there is anything special about X so that we can
> +    assume it already contains a truncated value of MODE.  */
> + 
> + bool
> + truncated_to_mode (enum machine_mode mode, rtx x)
> + {
> +   return REG_P (x) && rtl_hooks.reg_truncated_to_mode (mode, x);
> + }

This function is very small and will not be inlined.  Would you consider 
inlining it manually into the sole place where it is used?

Thanks,

Paolo