Patchwork [mips] Change the definition of macro SHIFT_COUNT_TRUNCATED

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Submitter Mingjie Xing
Date Sept. 3, 2010, 2:17 a.m.
Message ID <AANLkTim2mkV03TyZaPo62mUuGfzW_4NHzqYb9Ge_Wgu8@mail.gmail.com>
Download mbox | patch
Permalink /patch/63592/
State New
Headers show

Comments

Mingjie Xing - Sept. 3, 2010, 2:17 a.m.
2010/9/3 Richard Sandiford <rdsandiford@googlemail.com>:
> Mingjie Xing <mingjie.xing@gmail.com> writes:
>>         * config/mips/mips.h (SHIFT_COUNT_TRUNCATED): Change the definition.
>>         * config/mips/mips.c (mips_shift_truncation_mask): Implement
>>           TARGET_SHIFT_TRUNCATION_MASK.
>
> I think a more canonical version would be:
>
>        * config/mips/mips.h (SHIFT_COUNT_TRUNCATED): Change the definition.
>        * config/mips/mips.c (mips_shift_truncation_mask): New function.
>        (TARGET_SHIFT_TRUNCATION_MASK): Define.
>
>> Index: config/mips/mips.c
>> ===================================================================
>> --- config/mips/mips.c        (revision 163495)
>> +++ config/mips/mips.c        (working copy)
>> @@ -16335,6 +16335,20 @@ void mips_function_profiler (FILE *file)
>>      fprintf (file, "\tmove\t%s,%s\n", reg_names[STATIC_CHAIN_REGNUM],
>>            reg_names[2]);
>>  }
>> +
>> +/* Implement TARGET_SHIFT_TRUNCATION_MASK. We want to keep the current
>> +   behaviour of TARGET_SHIFT_TRUNCATION_MASK for non-vector modes even
>> +   when TARGET_LOONGSON_2EF is true. */
>
> s/current/default/, since we're writing this for future readers.
> Coding style says there should be two spaces after each sentence, so:
>
> /* Implement TARGET_SHIFT_TRUNCATION_MASK.  We want to keep the default
>   behaviour of TARGET_SHIFT_TRUNCATION_MASK for non-vector modes even
>   when TARGET_LOONGSON_2EF is true.  */
>
>>  /* Define this to be nonzero if shift instructions ignore all but the low-order
>>     few bits.  */
>> -#define SHIFT_COUNT_TRUNCATED 1
>> +#define SHIFT_COUNT_TRUNCATED (TARGET_LOONGSON_2EF ? 0 : 1)
>
> (!TARGET_LOONGSON_2EF)
>
> Please also document why we're doing this.  Let's do that by removing
> the current "Define this..." comment -- it's useless boilerplate --
> and replacing it with:
>
> /* Standard MIPS integer shifts truncate the shift amount to the
>   width of the shifted operand.  However, Loongson vector shifts
>   do not truncate the shift amount at all.  */
>
> OK with those changes, thanks.
>
> Richard
>

Oops, I remember my English teacher told me that there is one space
between two sentences. :-)

See the updated patch.

gcc/ChangeLog

       * config/mips/mips.h (SHIFT_COUNT_TRUNCATED): Change the definition.
       * config/mips/mips.c (mips_shift_truncation_mask): New function.
       (TARGET_SHIFT_TRUNCATION_MASK): Define.

gcc/testsuite/ChangeLog

       * gcc.target/mips/loongson-shift-count-truncated-1.c: New.

Best regards,
Mingjie
Richard Sandiford - Sept. 3, 2010, 8:08 a.m.
> gcc/ChangeLog
>
>       * config/mips/mips.h (SHIFT_COUNT_TRUNCATED): Change the definition.
>       * config/mips/mips.c (mips_shift_truncation_mask): New function.
>       (TARGET_SHIFT_TRUNCATION_MASK): Define.
>
> gcc/testsuite/ChangeLog
>
>       * gcc.target/mips/loongson-shift-count-truncated-1.c: New.

OK, thanks.

Richard
Mingjie Xing - Sept. 3, 2010, 9:33 a.m.
2010/9/3 Richard Sandiford <rdsandiford@googlemail.com>:
>> gcc/ChangeLog
>>
>>       * config/mips/mips.h (SHIFT_COUNT_TRUNCATED): Change the definition.
>>       * config/mips/mips.c (mips_shift_truncation_mask): New function.
>>       (TARGET_SHIFT_TRUNCATION_MASK): Define.
>>
>> gcc/testsuite/ChangeLog
>>
>>       * gcc.target/mips/loongson-shift-count-truncated-1.c: New.
>
> OK, thanks.
>
> Richard
>

Committed  revision 163799. Thanks a lot.

Mingjie

Patch

Index: testsuite/gcc.target/mips/loongson-shift-count-truncated-1.c
===================================================================
--- testsuite/gcc.target/mips/loongson-shift-count-truncated-1.c	(revision 0)
+++ testsuite/gcc.target/mips/loongson-shift-count-truncated-1.c	(revision 0)
@@ -0,0 +1,35 @@ 
+/* Test case for SHIFT_COUNT_TRUNCATED on Loongson.  */
+
+/* { dg-do run } */
+/* loongson.h does not handle or check for MIPS16ness.  There doesn't
+   seem any good reason for it to, given that the Loongson processors
+   do not support MIPS16.  */
+/* { dg-options "isa=loongson -mhard-float -mno-mips16 -O1" } */
+
+#include "loongson.h"
+#include <assert.h>
+
+typedef union { int32x2_t v; int32_t a[2]; } int32x2_encap_t;
+
+void
+main1 (int shift)
+{
+  int32x2_encap_t s;
+  int32x2_encap_t r;
+
+  s.a[0] = 0xffffffff;
+  s.a[1] = 0xffffffff;
+  /* Loongson SIMD use low-order 7 bits to specify the shift amount.
+     Thus V2SI << 0x40 == 0.  The below expression 'shift & 0x3f' will be
+     mis-optimized as 'shift', if SHIFT_COUNT_TRUNCATED is nonzero.  */
+  r.v = psllw_s (s.v, (shift & 0x3f));
+  assert (r.a[0] == 0xffffffff);
+  assert (r.a[1] == 0xffffffff);
+}
+
+int
+main (void)
+{
+  main1 (0x40);
+  return 0;
+}
Index: config/mips/mips.c
===================================================================
--- config/mips/mips.c	(revision 163495)
+++ config/mips/mips.c	(working copy)
@@ -16335,6 +16335,20 @@  void mips_function_profiler (FILE *file)
     fprintf (file, "\tmove\t%s,%s\n", reg_names[STATIC_CHAIN_REGNUM],
 	     reg_names[2]);
 }
+
+/* Implement TARGET_SHIFT_TRUNCATION_MASK.  We want to keep the default
+   behaviour of TARGET_SHIFT_TRUNCATION_MASK for non-vector modes even
+   when TARGET_LOONGSON_2EF is true.  */
+
+static unsigned HOST_WIDE_INT
+mips_shift_truncation_mask (enum machine_mode mode)
+{
+  if (TARGET_LOONGSON_2EF && VECTOR_MODE_P (mode))
+    return 0;
+
+  return GET_MODE_BITSIZE (mode) - 1;
+}
+
 
 /* Initialize the GCC target structure.  */
 #undef TARGET_ASM_ALIGNED_HI_OP
@@ -16539,6 +16553,9 @@  void mips_function_profiler (FILE *file)
 #undef TARGET_ASM_OUTPUT_SOURCE_FILENAME
 #define TARGET_ASM_OUTPUT_SOURCE_FILENAME mips_output_filename
 
+#undef TARGET_SHIFT_TRUNCATION_MASK
+#define TARGET_SHIFT_TRUNCATION_MASK mips_shift_truncation_mask
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 #include "gt-mips.h"
Index: config/mips/mips.h
===================================================================
--- config/mips/mips.h	(revision 163495)
+++ config/mips/mips.h	(working copy)
@@ -2444,9 +2444,10 @@  typedef struct mips_args {
    (often extended) would be needed for byte accesses.  */
 #define SLOW_BYTE_ACCESS (!TARGET_MIPS16)
 
-/* Define this to be nonzero if shift instructions ignore all but the low-order
-   few bits.  */
-#define SHIFT_COUNT_TRUNCATED 1
+/* Standard MIPS integer shifts truncate the shift amount to the
+   width of the shifted operand.  However, Loongson vector shifts
+   do not truncate the shift amount at all.  */
+#define SHIFT_COUNT_TRUNCATED (!TARGET_LOONGSON_2EF)
 
 /* Value is 1 if truncating an integer of INPREC bits to OUTPREC bits
    is done just by pretending it is already truncated.  */