Fix pessimistic DImode handling in combine.c:make_field_assignment

Fix pessimistic DImode handling in combine.c:make_field_assignment

[Richard Sandiford]

The make_field_assignment code:

      src = force_to_mode (src, mode,
		       GET_MODE_PRECISION (mode) >= HOST_BITS_PER_WIDE_INT
		       ? HOST_WIDE_INT_M1U
		       : (HOST_WIDE_INT_1U << len) - 1,
		       0);

would ignore the field length len for DImode, even though DImode can be
handled using HWIs.  I think the code should be testing len instead.

The patch was originally part of the SVE machine_mode series.
Retesting showed that it changed the asm output on powerpc for a few
tests, so I thought it should go in separately.  Each test change
seemed to be an improvement.

Tested on aarch64-linux-gnu and x86_64-linux-gnu.  I no longer have
access to the compile farm to test on the powerpc boxes there.

Thanks,
Richard


2017-05-24  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* combine.c (make_field_assignment): Check len rather than the mode
	precision when calling force_to_mode.

Index: gcc/combine.c
===================================================================
--- gcc/combine.c	2017-05-03 08:46:32.777861592 +0100
+++ gcc/combine.c	2017-05-24 09:25:25.170351268 +0100
@@ -9634,7 +9634,7 @@ make_field_assignment (rtx x)
 						     other, pos),
 			       dest);
   src = force_to_mode (src, mode,
-		       GET_MODE_PRECISION (mode) >= HOST_BITS_PER_WIDE_INT
+		       len >= HOST_BITS_PER_WIDE_INT
 		       ? HOST_WIDE_INT_M1U
 		       : (HOST_WIDE_INT_1U << len) - 1,
 		       0);

Re: Fix pessimistic DImode handling in combine.c:make_field_assignment

[Richard Sandiford]

Richard Sandiford <richard.sandiford@linaro.org> writes:
> The make_field_assignment code:
>
>       src = force_to_mode (src, mode,
> 		       GET_MODE_PRECISION (mode) >= HOST_BITS_PER_WIDE_INT
> 		       ? HOST_WIDE_INT_M1U
> 		       : (HOST_WIDE_INT_1U << len) - 1,
> 		       0);
>
> would ignore the field length len for DImode, even though DImode can be
> handled using HWIs.  I think the code should be testing len instead.
>
> The patch was originally part of the SVE machine_mode series.
> Retesting showed that it changed the asm output on powerpc for a few
> tests, so I thought it should go in separately.  Each test change
> seemed to be an improvement.
>
> Tested on aarch64-linux-gnu and x86_64-linux-gnu.  I no longer have
> access to the compile farm to test on the powerpc boxes there.

Now tested on powerpc64le-linux-gnu too (thanks to Segher for the access).

> Thanks,
> Richard
>
>
> 2017-05-24  Richard Sandiford  <richard.sandiford@linaro.org>
>
> gcc/
> 	* combine.c (make_field_assignment): Check len rather than the mode
> 	precision when calling force_to_mode.
>
> Index: gcc/combine.c
> ===================================================================
> --- gcc/combine.c	2017-05-03 08:46:32.777861592 +0100
> +++ gcc/combine.c	2017-05-24 09:25:25.170351268 +0100
> @@ -9634,7 +9634,7 @@ make_field_assignment (rtx x)
>  						     other, pos),
>  			       dest);
>    src = force_to_mode (src, mode,
> -		       GET_MODE_PRECISION (mode) >= HOST_BITS_PER_WIDE_INT
> +		       len >= HOST_BITS_PER_WIDE_INT
>  		       ? HOST_WIDE_INT_M1U
>  		       : (HOST_WIDE_INT_1U << len) - 1,
>  		       0);

Re: Fix pessimistic DImode handling in combine.c:make_field_assignment

[Richard Sandiford]

Ping

Richard Sandiford <richard.sandiford@linaro.org> writes:
> Richard Sandiford <richard.sandiford@linaro.org> writes:
>> The make_field_assignment code:
>>
>>       src = force_to_mode (src, mode,
>> 		       GET_MODE_PRECISION (mode) >= HOST_BITS_PER_WIDE_INT
>> 		       ? HOST_WIDE_INT_M1U
>> 		       : (HOST_WIDE_INT_1U << len) - 1,
>> 		       0);
>>
>> would ignore the field length len for DImode, even though DImode can be
>> handled using HWIs.  I think the code should be testing len instead.
>>
>> The patch was originally part of the SVE machine_mode series.
>> Retesting showed that it changed the asm output on powerpc for a few
>> tests, so I thought it should go in separately.  Each test change
>> seemed to be an improvement.
>>
>> Tested on aarch64-linux-gnu and x86_64-linux-gnu.  I no longer have
>> access to the compile farm to test on the powerpc boxes there.
>
> Now tested on powerpc64le-linux-gnu too (thanks to Segher for the access).
>
>> Thanks,
>> Richard
>>
>>
>> 2017-05-24  Richard Sandiford  <richard.sandiford@linaro.org>
>>
>> gcc/
>> 	* combine.c (make_field_assignment): Check len rather than the mode
>> 	precision when calling force_to_mode.
>>
>> Index: gcc/combine.c
>> ===================================================================
>> --- gcc/combine.c	2017-05-03 08:46:32.777861592 +0100
>> +++ gcc/combine.c	2017-05-24 09:25:25.170351268 +0100
>> @@ -9634,7 +9634,7 @@ make_field_assignment (rtx x)
>>  						     other, pos),
>>  			       dest);
>>    src = force_to_mode (src, mode,
>> -		       GET_MODE_PRECISION (mode) >= HOST_BITS_PER_WIDE_INT
>> +		       len >= HOST_BITS_PER_WIDE_INT
>>  		       ? HOST_WIDE_INT_M1U
>>  		       : (HOST_WIDE_INT_1U << len) - 1,
>>  		       0);

Re: Fix pessimistic DImode handling in combine.c:make_field_assignment

[Eric Botcazou]

> 2017-05-24  Richard Sandiford  <richard.sandiford@linaro.org>
> 
> gcc/
> 	* combine.c (make_field_assignment): Check len rather than the mode
> 	precision when calling force_to_mode.

OK for mainline.

-- 
Eric Botcazou