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[PATCH][ARM] PR target/69857 Remove bogus early return false; in gen_operands_ldrd_strd
- From: Kyrill Tkachov <kyrylo dot tkachov at foss dot arm dot com>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Cc: Ramana Radhakrishnan <ramana dot radhakrishnan at arm dot com>, Richard Earnshaw <Richard dot Earnshaw at arm dot com>
- Date: Tue, 24 May 2016 09:52:48 +0100
- Subject: [PATCH][ARM] PR target/69857 Remove bogus early return false; in gen_operands_ldrd_strd
- Authentication-results: sourceware.org; auth=none
Hi all,
As the PR says, the gen_operands_ldrd_strd function has a spurious return false in it.
It seems to have been there from the beginning when that code was added.
The code is trying to transform:
mov r0, 0
str r0, [r2]
mov r0, 1
str r0, [r2, #4]
into:
mov r0, 0
mov r1, 1
strd r0, r1, [r2]
but thanks to this return only works on Thumb2.
This means that the path it was not getting tested, and we weren't generating
as many STRD instructions as we could when compiling with -marm.
This patch removes the spurious return. It also re-indents the comment for this
transformation (replacing 8 spaces with tab) and adds a mention of the behaviour
for ARM state that was missing.
With it bootstrap and test in arm state on arm-none-linux-gnueabihf runs fine.
Across all of SPEC2006 this increased the number of STRD instructions used by 0.12%
(from 121375 -> 121530)
Ok for trunk?
Thanks,
Kyrill
2016-05-24 Kyrylo Tkachov <kyrylo.tkachov@arm.com>
PR target/69857
* config/arm/arm.c (gen_operands_ldrd_strd): Remove bogus early
return. Reindent transformation comment and mention the ARM state
behavior.
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 089d1483ac534cfd7693fdd309149aa5e8bf8191..fe1c37cda62fa76ef9438208e39b3a91e7161972 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -15985,14 +15985,17 @@ gen_operands_ldrd_strd (rtx *operands, bool load,
/* If the same input register is used in both stores
when storing different constants, try to find a free register.
For example, the code
- mov r0, 0
- str r0, [r2]
- mov r0, 1
- str r0, [r2, #4]
+ mov r0, 0
+ str r0, [r2]
+ mov r0, 1
+ str r0, [r2, #4]
can be transformed into
- mov r1, 0
- strd r1, r0, [r2]
- in Thumb mode assuming that r1 is free. */
+ mov r1, 0
+ mov r0, 1
+ strd r1, r0, [r2]
+ in Thumb mode assuming that r1 is free.
+ For ARM mode do the same but only if the starting register
+ can be made to be even. */
if (const_store
&& REGNO (operands[0]) == REGNO (operands[1])
&& INTVAL (operands[4]) != INTVAL (operands[5]))
@@ -16011,7 +16014,6 @@ gen_operands_ldrd_strd (rtx *operands, bool load,
}
else if (TARGET_ARM)
{
- return false;
int regno = REGNO (operands[0]);
if (!peep2_reg_dead_p (4, operands[0]))
{