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[PATCH] combine: Don't create (set (reg:CC) (compare (reg:CC) (const0)))
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: gcc-patches at gcc dot gnu dot org
- Cc: rth at redhat dot com, Segher Boessenkool <segher at kernel dot crashing dot org>
- Date: Mon, 11 May 2015 06:13:40 -0700
- Subject: [PATCH] combine: Don't create (set (reg:CC) (compare (reg:CC) (const0)))
- Authentication-results: sourceware.org; auth=none
There already was code to just use the original reg:CC, but it was
positioned incorrectly: if the original code (that this RTL is
simplified from) did not already start with a COMPARE (or not in
the right mode), it didn't trigger. But it is valid in that case
as well.
This then allows merging the other two arms of this conditional;
do so.
Bootstrapped and regression tested on powerpc64-linux and x86_64-linux;
no regressions. Also built toolchains and Linux kernels for every
arch where that works; no new failures on that.
Any objections?
Segher
2015-05-11 Segher Boessenkool <segher@kernel.crashing.org>
* combine.c (simplify_set): When generating a CC set, if the
source already is in the correct mode, do not wrap it in a
compare. Simplify the rest of that code.
---
gcc/combine.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)
diff --git a/gcc/combine.c b/gcc/combine.c
index 896d9d2..51f78a5 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -6675,20 +6675,16 @@ simplify_set (rtx x)
if (other_changed)
undobuf.other_insn = other_insn;
- /* Otherwise, if we didn't previously have a COMPARE in the
- correct mode, we need one. */
- if (GET_CODE (src) != COMPARE || GET_MODE (src) != compare_mode)
- {
- SUBST (SET_SRC (x), gen_rtx_COMPARE (compare_mode, op0, op1));
- src = SET_SRC (x);
- }
- else if (GET_MODE (op0) == compare_mode && op1 == const0_rtx)
+ /* Don't generate a compare of a CC with 0, just use that CC. */
+ if (GET_MODE (op0) == compare_mode && op1 == const0_rtx)
{
SUBST (SET_SRC (x), op0);
src = SET_SRC (x);
}
- /* Otherwise, update the COMPARE if needed. */
- else if (XEXP (src, 0) != op0 || XEXP (src, 1) != op1)
+ /* Otherwise, if we didn't previously have the same COMPARE we
+ want, create it from scratch. */
+ else if (GET_CODE (src) != COMPARE || GET_MODE (src) != compare_mode
+ || XEXP (src, 0) != op0 || XEXP (src, 1) != op1)
{
SUBST (SET_SRC (x), gen_rtx_COMPARE (compare_mode, op0, op1));
src = SET_SRC (x);
--
1.8.1.4