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Re: [PATCH] Improve the mode which is used for insertion


On Tue, Sep 4, 2012 at 12:33 AM, Andrew Pinski
<> wrote:
> Hi,
>   On MIPS it is better sometimes not to use the word mode (DImode) but
> rather SImode.  The main reason is for 32bits, the value has to be
> sign extended to 64bits so using the 32bit instruction for insertion
> is allows for that to happen automatically.
> This patch implements this by adding a target hook which returns the
> modes which are valid for doing the insertion and modifying
> store_bit_field_1 to use them if they exists.
> OK?  Bootstrapped and tested on both x86_64-linux-gnu and
> mips64-linux-gnu with no regressions.
> Thanks,
> Andrew Pinski
>         * target.h (gcc_target): Add mode_for_extraction_insv.
>         * expmed.c (store_bit_field_1): Use mode_for_extraction_insv
>         and split out into ...
>         (store_bit_field_2): Here.
>         * target-def.h (TARGET_MODE_FOR_EXTRACTION_INSV): Define.
>         * config/mips/mips.c (mips_mode_for_extraction_insv): New function.

This one has a problem for targets with !HAVE_insv since on those
mode_for_extraction (EP_insv, 3) returns an invalid machine_mode and
thus GET_MODE_BITSIZE (op_mode) is undefined since a value outside
array boundaries is accessed. To fix this I put the following change
on top:

diff --git a/gcc/expmed.c b/gcc/expmed.c
index 6afafd3..a55b2a8 100644
--- a/gcc/expmed.c
+++ b/gcc/expmed.c
@@ -361,7 +361,8 @@ store_bit_field_2 (rtx str_rtx, unsigned
HOST_WIDE_INT bitsize,
   rtx op0 = str_rtx;
   int byte_offset;
   rtx orig_value;
-  unsigned int unit = (MEM_P (str_rtx)) ? BITS_PER_UNIT :
+  unsigned int unit = (MEM_P (str_rtx)) ? BITS_PER_UNIT :
+    (HAVE_insv ? GET_MODE_BITSIZE (op_mode) : BITS_PER_WORD);

   while (GET_CODE (op0) == SUBREG)


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