From: HAO CHEN GUI <guihaoc@linux.ibm.com>
To: gcc-patches <gcc-patches@gcc.gnu.org>
Cc: Segher Boessenkool <segher@kernel.crashing.org>,
David <dje.gcc@gmail.com>, "Kewen.Lin" <linkw@linux.ibm.com>,
Peter Bergner <bergner@linux.ibm.com>
Subject: [rs6000, patch] Enable have_cbranchcc4 on rs6000
Date: Wed, 16 Nov 2022 10:32:42 +0800 [thread overview]
Message-ID: <153badc6-8afc-0695-32b2-ab5a9e0a161d@linux.ibm.com> (raw)
Hi,
The patch enables have_cbrnachcc4 which is a flag in ifcvt.cc to
indicate if branch by CC bits is invalid or not. As rs6000 already has
"*cbranch" insn which does branching according to CC bits, the flag
should be enabled and relevant branches can be optimized out. The test
case illustrates the optimization.
"*cbranch" is an anonymous insn which can't be generated directly.
So changing "const_int 0" to the third operand predicated by
"zero_constant" won't cause ICEs as orginal patterns still can be matched.
Bootstrapped and tested on powerpc64-linux BE and LE with no regressions.
Is this okay for trunk? Any recommendations? Thanks a lot.
ChangeLog
2022-11-16 Haochen Gui <guihaoc@linux.ibm.com>
gcc/
* config/rs6000/rs6000.md (*cbranch): Rename to...
(cbranchcc4): ...this, and set const_int 0 to the third operand.
gcc/testsuite/
* gcc.target/powerpc/cbranchcc4.c: New.
patch.diff
diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index e9e5cd1e54d..ee171f21f6a 100644
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -13067,11 +13067,11 @@ (define_insn_and_split "*<code><mode>_cc"
;; Conditional branches.
;; These either are a single bc insn, or a bc around a b.
-(define_insn "*cbranch"
+(define_insn "cbranchcc4"
[(set (pc)
(if_then_else (match_operator 1 "branch_comparison_operator"
[(match_operand 2 "cc_reg_operand" "y")
- (const_int 0)])
+ (match_operand 3 "zero_constant")])
(label_ref (match_operand 0))
(pc)))]
""
diff --git a/gcc/testsuite/gcc.target/powerpc/cbranchcc4.c b/gcc/testsuite/gcc.target/powerpc/cbranchcc4.c
new file mode 100644
index 00000000000..1751d274bbf
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/cbranchcc4.c
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-rtl-ce1" } */
+/* { dg-final {scan-rtl-dump "noce_try_store_flag_constants" "ce1" } } */
+
+int test (unsigned int a, unsigned int b)
+{
+ return (a < b ? 0 : (a > b ? 2 : 1));
+}
next reply other threads:[~2022-11-16 2:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-16 2:32 HAO CHEN GUI [this message]
2022-11-16 3:04 ` David Edelsohn
2022-11-16 5:55 ` HAO CHEN GUI
2022-11-16 12:59 ` David Edelsohn
2022-11-16 12:06 ` Segher Boessenkool
2022-11-16 12:13 ` Segher Boessenkool
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