From: Richard Henderson <rth@redhat.com>
To: gcc-patches@gcc.gnu.org
Cc: David Edelsohn <dje.gcc@gmail.com>
Subject: [PATCH 07/15] rs6000: Generalize left shift in constant generation
Date: Wed, 12 Aug 2015 01:12:00 -0000 [thread overview]
Message-ID: <1439341904-9345-8-git-send-email-rth@redhat.com> (raw)
In-Reply-To: <1439341904-9345-1-git-send-email-rth@redhat.com>
Rather than always shift by 32, shift by the total number of zeros required.
The improvement to also look to shift out ones comes from Kenner via alpha.
Cc: David Edelsohn <dje.gcc@gmail.com>
---
* config/rs6000/rs6000.c (genimm_ppc::exam_search): Use ctz to
compute the shift. Also attempt to shift out ones.
---
gcc/config/rs6000/rs6000.c | 21 +++++++++++++++++----
1 file changed, 17 insertions(+), 4 deletions(-)
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 59c5014..b27e476 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -8145,6 +8145,7 @@ genimm_ppc::exam_search (HOST_WIDE_INT c, int budget)
{
const int sub_budget = budget - 1;
HOST_WIDE_INT test;
+ int bits;
/* Simple arithmetic on the low 32-bits. */
test = c & 0xffff;
@@ -8181,11 +8182,23 @@ genimm_ppc::exam_search (HOST_WIDE_INT c, int budget)
}
/* Shift the constant left. */
- test = HOST_WIDE_INT_UC (0xffffffff00000000);
- if ((c & test) == c && exam_sub (c >> 32, sub_budget))
+ bits = ctz_hwi (c);
+ if (bits > 0)
{
- opN (ASHIFT, 32); /* SLDI */
- return true;
+ /* First try with zeros being shifted out. */
+ HOST_WIDE_INT sub_c = (unsigned HOST_WIDE_INT)c >> bits;
+ bool ok = exam_sub (sub_c, sub_budget);
+ if (!ok)
+ {
+ /* If that failed, try with ones being shifted out. */
+ sub_c |= ~(HOST_WIDE_INT_M1U >> bits);
+ ok = exam_sub (sub_c, sub_budget);
+ }
+ if (ok)
+ {
+ opN (ASHIFT, bits); /* SLDI */
+ return true;
+ }
}
return false;
--
2.4.3
next prev parent reply other threads:[~2015-08-12 1:11 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-12 1:11 [PATCH ppc64,aarch64,alpha 00/15] Improve backend " Richard Henderson
2015-08-12 1:11 ` [PATCH 01/15] rs6000: Split out rs6000_is_valid_and_mask_wide Richard Henderson
2015-08-12 13:24 ` Segher Boessenkool
2015-08-12 15:50 ` Richard Henderson
2015-08-13 2:29 ` Segher Boessenkool
2015-08-12 1:11 ` [PATCH 05/15] rs6000: Move constant via mask into build_set_const_data Richard Henderson
2015-08-12 1:12 ` [PATCH 12/15] aarch64: Test for duplicated 32-bit halves Richard Henderson
2015-08-12 1:12 ` [PATCH 15/15] alpha: Remove alpha_emit_set_long_const Richard Henderson
2015-08-12 1:12 ` [PATCH 13/15] alpha: Use hashing infrastructure for generating constants Richard Henderson
2015-08-12 1:12 ` [PATCH 02/15] rs6000: Make num_insns_constant_wide static Richard Henderson
2015-08-12 1:12 ` [PATCH 04/15] rs6000: Implement set_const_data infrastructure Richard Henderson
2015-08-12 13:53 ` Segher Boessenkool
2015-08-12 1:12 ` [PATCH 09/15] rs6000: Use xoris in constant construction Richard Henderson
2015-08-12 1:12 ` [PATCH 03/15] rs6000: Tidy num_insns_constant vs CONST_DOUBLE Richard Henderson
2015-08-12 1:12 ` [PATCH 11/15] aarch64: Use hashing infrastructure for generating constants Richard Henderson
2015-08-12 1:12 ` [PATCH 06/15] rs6000: Use rldiwi in constant construction Richard Henderson
2015-08-12 14:02 ` Segher Boessenkool
2015-08-12 15:55 ` Richard Henderson
2015-08-13 2:43 ` Segher Boessenkool
2015-08-13 19:01 ` Mike Stump
2015-08-13 20:30 ` Joseph Myers
2015-08-12 1:12 ` [PATCH 08/15] rs6000: Generalize masking in constant generation Richard Henderson
2015-08-12 1:12 ` [PATCH 10/15] rs6000: Use rotldi " Richard Henderson
2015-08-12 1:12 ` [PATCH 14/15] alpha: Split out alpha_cost_set_const Richard Henderson
2015-08-12 1:12 ` Richard Henderson [this message]
2015-08-12 8:32 ` [PATCH ppc64,aarch64,alpha 00/15] Improve backend constant generation Segher Boessenkool
2015-08-12 15:32 ` Richard Henderson
2015-08-13 3:07 ` Segher Boessenkool
2015-08-13 5:36 ` Segher Boessenkool
2015-08-13 3:10 ` Segher Boessenkool
2015-08-13 11:32 ` David Edelsohn
2015-08-12 8:32 ` Richard Earnshaw
2015-08-12 8:43 ` Richard Earnshaw
2015-08-12 9:02 ` Richard Earnshaw
2015-08-12 15:45 ` Richard Henderson
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