Re: [42/77] Use scalar_int_mode in simplify_shift_const_1

[Jeff Law]

On 07/13/2017 02:53 AM, Richard Sandiford wrote:
> This patch makes simplify_shift_const_1 use scalar_int_modes
> for all code that is specific to scalars rather than vectors.
> This includes situations in which the new shift mode is different
> from the original one, since the function never changes the mode
> of vector shifts.  That in turn makes it more natural to test for
> equal modes in simplify_shift_const_1 rather than try_widen_shift_mode
> (which only applies to scalars).
> 
> 2017-07-13  Richard Sandiford  
>   Alan Hayward  
>   David Sherwood  
> 
> gcc/
>   * combine.c (try_widen_shift_mode): Move check for equal modes to...
>   (simplify_shift_const_1): ...here.  Use scalar_int_mode for
>   shift_unit_mode and for modes involved in scalar shifts.
OK.
Jeff

[42/77] Use scalar_int_mode in simplify_shift_const_1

[Richard Sandiford]

This patch makes simplify_shift_const_1 use scalar_int_modes
for all code that is specific to scalars rather than vectors.
This includes situations in which the new shift mode is different
from the original one, since the function never changes the mode
of vector shifts.  That in turn makes it more natural to test for
equal modes in simplify_shift_const_1 rather than try_widen_shift_mode
(which only applies to scalars).

2017-07-13  Richard Sandiford  
Alan Hayward  
David Sherwood  

gcc/
* combine.c (try_widen_shift_mode): Move check for equal modes to...
(simplify_shift_const_1): ...here.  Use scalar_int_mode for
shift_unit_mode and for modes involved in scalar shifts.

Index: gcc/combine.c
===
--- gcc/combine.c   2017-07-13 09:18:42.622481204 +0100
+++ gcc/combine.c   2017-07-13 09:18:43.037447143 +0100
@@ -10343,8 +10343,6 @@ try_widen_shift_mode (enum rtx_code code
  machine_mode orig_mode, machine_mode mode,
  enum rtx_code outer_code, HOST_WIDE_INT outer_const)
 {
-  if (orig_mode == mode)
-return mode;
   gcc_assert (GET_MODE_PRECISION (mode) > GET_MODE_PRECISION (orig_mode));
 
   /* In general we can't perform in wider mode for right shift and rotate.  */
@@ -10405,7 +10403,7 @@ simplify_shift_const_1 (enum rtx_code co
   int count;
   machine_mode mode = result_mode;
   machine_mode shift_mode;
-  scalar_int_mode tmode, inner_mode;
+  scalar_int_mode tmode, inner_mode, int_mode, int_varop_mode, int_result_mode;
   unsigned int mode_words
 = (GET_MODE_SIZE (mode) + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD;
   /* We form (outer_op (code varop count) (outer_const)).  */
@@ -10445,9 +10443,19 @@ simplify_shift_const_1 (enum rtx_code co
  count = bitsize - count;
}
 
-  shift_mode = try_widen_shift_mode (code, varop, count, result_mode,
-mode, outer_op, outer_const);
-  machine_mode shift_unit_mode = GET_MODE_INNER (shift_mode);
+  shift_mode = result_mode;
+  if (shift_mode != mode)
+   {
+ /* We only change the modes of scalar shifts.  */
+ int_mode = as_a  (mode);
+ int_result_mode = as_a  (result_mode);
+ shift_mode = try_widen_shift_mode (code, varop, count,
+int_result_mode, int_mode,
+outer_op, outer_const);
+   }
+
+  scalar_int_mode shift_unit_mode
+   = as_a  (GET_MODE_INNER (shift_mode));
 
   /* Handle cases where the count is greater than the size of the mode
 minus 1.  For ASHIFT, use the size minus one as the count (this can
@@ -10542,6 +10550,7 @@ simplify_shift_const_1 (enum rtx_code co
  /* The following rules apply only to scalars.  */
  if (shift_mode != shift_unit_mode)
break;
+ int_mode = as_a  (mode);
 
  /* If we have (xshiftrt (mem ...) C) and C is MODE_WIDTH
 minus the width of a smaller mode, we can do this with a
@@ -10550,15 +10559,15 @@ simplify_shift_const_1 (enum rtx_code co
  && ! mode_dependent_address_p (XEXP (varop, 0),
 MEM_ADDR_SPACE (varop))
  && ! MEM_VOLATILE_P (varop)
- && (int_mode_for_size (GET_MODE_BITSIZE (mode) - count, 1)
+ && (int_mode_for_size (GET_MODE_BITSIZE (int_mode) - count, 1)
  .exists ()))
{
  new_rtx = adjust_address_nv (varop, tmode,
-  BYTES_BIG_ENDIAN ? 0
-  : count / BITS_PER_UNIT);
+  BYTES_BIG_ENDIAN ? 0
+  : count / BITS_PER_UNIT);
 
  varop = gen_rtx_fmt_e (code == ASHIFTRT ? SIGN_EXTEND
-: ZERO_EXTEND, mode, new_rtx);
+: ZERO_EXTEND, int_mode, new_rtx);
  count = 0;
  continue;
}
@@ -10568,20 +10577,22 @@ simplify_shift_const_1 (enum rtx_code co
  /* The following rules apply only to scalars.  */
  if (shift_mode != shift_unit_mode)
break;
+ int_mode = as_a  (mode);
+ int_varop_mode = as_a  (GET_MODE (varop));
 
  /* If VAROP is a SUBREG, strip it as long as the inner operand has
 the same number of words as what we've seen so far.  Then store
 the widest mode in MODE.  */
  if (subreg_lowpart_p (varop)
  && is_int_mode (GET_MODE (SUBREG_REG (varop)), _mode)
- && GET_MODE_SIZE (inner_mode) > GET_MODE_SIZE (GET_MODE (varop))
+ && GET_MODE_SIZE (inner_mode) > GET_MODE_SIZE (int_varop_mode)
  &&