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combine.c (simplify_shift_const): Revert previous two changes.

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* combine.c (simplify_shift_const): Revert previous two
        changes.  If SHIFT_COUNT_TRUNCATED, crop the shift count
        before the main loop.

From-SVN: r35742
This commit is contained in:
Richard Henderson 2000-08-16 00:56:04 -07:00 • committed by Richard Henderson
parent cbd273a803
commit 853d88280a
2 changed files with 18 additions and 15 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2000-08-16 Richard Henderson <rth@cygnus.com>
* combine.c (simplify_shift_const): Revert previous two
changes. If SHIFT_COUNT_TRUNCATED, crop the shift count
before the main loop.
2000-08-15 Richard Henderson <rth@cygnus.com> 2000-08-15 Richard Henderson <rth@cygnus.com>
* combine.c (simplify_shift_const): Bound shift count when * combine.c (simplify_shift_const): Bound shift count when

27
gcc/combine.c
View file

@ -8851,6 +8851,14 @@ simplify_shift_const (x, code, result_mode, varop, input_count)
count = input_count; count = input_count;
/* Make sure and truncate the "natural" shift on the way in. We don't
want to do this inside the loop as it makes it more difficult to
combine shifts. */
#ifdef SHIFT_COUNT_TRUNCATED
if (SHIFT_COUNT_TRUNCATED)
count %= GET_MODE_BITSIZE (mode);
#endif
/* Unless one of the branches of the `if' in this loop does a `continue', /* Unless one of the branches of the `if' in this loop does a `continue',
we will `break' the loop after the `if'. */ we will `break' the loop after the `if'. */
@ -8879,11 +8887,10 @@ simplify_shift_const (x, code, result_mode, varop, input_count)
? result_mode : mode); ? result_mode : mode);
/* Handle cases where the count is greater than the size of the mode /* Handle cases where the count is greater than the size of the mode
minus 1. If SHIFT_COUNT_TRUNCATED, there aren't really any such minus 1. For ASHIFT, use the size minus one as the count (this can
cases. Otherwise, for ASHIFT, use the size minus one as the count occur when simplifying (lshiftrt (ashiftrt ..))). For rotates,
(this can occur when simplifying (lshiftrt (ashiftrt ..))). For take the count modulo the size. For other shifts, the result is
rotates, take the count modulo the size. For other shifts, the zero.
result is zero.
Since these shifts are being produced by the compiler by combining Since these shifts are being produced by the compiler by combining
multiple operations, each of which are defined, we know what the multiple operations, each of which are defined, we know what the
@ -8891,11 +8898,6 @@ simplify_shift_const (x, code, result_mode, varop, input_count)
if (count > GET_MODE_BITSIZE (shift_mode) - 1) if (count > GET_MODE_BITSIZE (shift_mode) - 1)
{ {
#ifdef SHIFT_COUNT_TRUNCATED
if (SHIFT_COUNT_TRUNCATED)
count %= GET_MODE_BITSIZE (shift_mode);
else
#endif
if (code == ASHIFTRT) if (code == ASHIFTRT)
count = GET_MODE_BITSIZE (shift_mode) - 1; count = GET_MODE_BITSIZE (shift_mode) - 1;
else if (code == ROTATE || code == ROTATERT) else if (code == ROTATE || code == ROTATERT)
@ -9149,8 +9151,6 @@ simplify_shift_const (x, code, result_mode, varop, input_count)
break; break;
count += first_count; count += first_count;
if (count >= GET_MODE_BITSIZE (shift_mode))
count = GET_MODE_BITSIZE (shift_mode) - 1;
varop = XEXP (varop, 0); varop = XEXP (varop, 0);
continue; continue;
} }
@ -9204,9 +9204,6 @@ simplify_shift_const (x, code, result_mode, varop, input_count)
else else
count = signed_count; count = signed_count;
if (count >= GET_MODE_BITSIZE (shift_mode))
count = GET_MODE_BITSIZE (shift_mode) - 1;
varop = XEXP (varop, 0); varop = XEXP (varop, 0);
continue; continue;
} }