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Re: [PATCH, ARM, LRA] Prepare ARM build with LRA


> So can we assert that we have a REG here and use GET_MODE (XEXP (x, 0))?  Or
> else return false if we don't have a REG.

I'm currently testing the patch with the modification below

+static bool
+lsb_bitfield_op_p (rtx x)
+{
+  if (GET_RTX_CLASS (GET_CODE (x)) == RTX_BITFIELD_OPS)
+    {
+      enum machine_mode mode = GET_MODE(XEXP (x, 0));
+      unsigned HOST_WIDE_INT len = INTVAL (XEXP (x, 1));
+      HOST_WIDE_INT pos = INTVAL (XEXP (x, 2));
+
+      return (pos == (BITS_BIG_ENDIAN ? GET_MODE_PRECISION (mode) - len : 0));
+    }
+  return false;
+}


>> According to gcc internals, ROTATE and ROTATERT are similar to the
>> shifting operations, but to be more accurate maybe we can rename
>> shif_code_p in shift_and _rotate_code_p rotation are used in arm
>> address calculation, and thus need to be handle in  must_be_index_p
>> and set_address_index
>
> Egad.  I guess I just wanted to see it written down. :-)

Sorry, I'm not sure I understand well, it means that you prefer the
shift_and _rotate_code_p notation, right ?

> Btw, are you sure that you don't need to modify must_be_index_p instead?
>
> /* Return true if X must be an index rather than a base.  */
>
> static bool
> must_be_index_p (rtx x)
> {
>   return GET_CODE (x) == MULT || GET_CODE (x) == ASHIFT;
> }
>
> and call it from set_address_index?

Yes, if we don't modify must_be_index_p we'll have failures when
enabling LRA on ARM.  You can find an history if the patch in the
thread named "RFC: patch to build GCC for arm with LRA" which started
more or less here :

http://gcc.gnu.org/ml/gcc-patches/2013-09/msg00526.html

Thanks,
Yvan

> --
> Eric Botcazou


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