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Re: [PATCH 2/2] Enable elimination of zext/sext


On Wed, Aug 27, 2014 at 12:07 PM, Richard Biener
<richard.guenther@gmail.com> wrote:
>> 2014-08-07  Kugan Vivekanandarajah  <kuganv@linaro.org>
>>>
>>> * calls.c (precompute_arguments): Check
>>> promoted_for_signed_and_unsigned_p and set the promoted mode.
>>> (promoted_for_signed_and_unsigned_p): New function.
>>> (expand_expr_real_1): Check promoted_for_signed_and_unsigned_p
>>> and set the promoted mode.
>>> * expr.h (promoted_for_signed_and_unsigned_p): New function definition.
>>> * cfgexpand.c (expand_gimple_stmt_1): Call emit_move_insn if
>>> SUBREG is promoted with SRP_SIGNED_AND_UNSIGNED.
>>
>> This patch regresses:
>>
>> Running target unix
>> FAIL: libgomp.fortran/simd7.f90   -O2  execution test
>> FAIL: libgomp.fortran/simd7.f90   -Os  execution test
>>
>> on alphaev6-linux-gnu.
>>
>> So, the code assumes that it is possible to copy (reg:DI 540) directly
>> to (reg:DI 154). However, this is not the case, since we still have
>> garbage in the top 32bits.
>>
>> Reverting the part above fixes the runtime failure, since (insn 599) is now:
>>
>> (insn 599 598 0 (set (reg:DI 145 [ D.1694 ])
>>         (zero_extend:DI (subreg:SI (reg:DI 540) 0))) -1
>>      (nil))
>>
>> It looks to me that we have also to check the temp with SUBREG_PROMOTED_*.
>
> Yeah, that makes sense.

Something like following (untested) patch that also fixes the testcase perhaps?

-- cut here--
Index: cfgexpand.c
===================================================================
--- cfgexpand.c (revision 214445)
+++ cfgexpand.c (working copy)
@@ -3322,6 +3322,7 @@ expand_gimple_stmt_1 (gimple stmt)

                if ((SUBREG_PROMOTED_GET (target) == SRP_SIGNED_AND_UNSIGNED)
                    && (GET_CODE (temp) == SUBREG)
+                   && SUBREG_PROMOTED_VAR_P (temp)
                    && (GET_MODE (target) == GET_MODE (temp))
                    && (GET_MODE (SUBREG_REG (target)) == GET_MODE
(SUBREG_REG (temp))))
                  emit_move_insn (SUBREG_REG (target), SUBREG_REG (temp));
-- cut here

Uros.


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