The attached patch enables using r1 to r4 as the literal pool base pointer if
one of them is unused in a leaf function. The unpatched code supports only r5
and r13.
Ciao
Dominik ^_^ ^_^
--
Dominik Vogt
IBM Germany
gcc/ChangeLog
* config/s390/s390.c (s390_init_frame_layout): Allow to use r1, ..., r4
as base register for the literal pool too.
>From f2838924c4c02eeabfdf7d8b79bd7a7ce8228e06 Mon Sep 17 00:00:00 2001
From: Dominik Vogt <v...@linux.vnet.ibm.com>
Date: Fri, 11 Dec 2015 11:33:23 +0100
Subject: [PATCH] S/390: Allow to use r1 to r4 as literal pool base
pointer.
The old code only considered r5 and r13.
---
gcc/config/s390/s390.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/gcc/config/s390/s390.c b/gcc/config/s390/s390.c
index bc6f05b..b195ad3d 100644
--- a/gcc/config/s390/s390.c
+++ b/gcc/config/s390/s390.c
@@ -9543,10 +9543,17 @@ s390_init_frame_layout (void)
as base register to avoid save/restore overhead. */
if (!base_used)
cfun->machine->base_reg = NULL_RTX;
- else if (crtl->is_leaf && !df_regs_ever_live_p (5))
- cfun->machine->base_reg = gen_rtx_REG (Pmode, 5);
else
- cfun->machine->base_reg = gen_rtx_REG (Pmode, BASE_REGNUM);
+ {
+ int br = 0;
+
+ if (crtl->is_leaf)
+ /* Prefer r5 (most likely to be free). */
+ for (br = 5; br >= 1 && df_regs_ever_live_p (br); br--)
+ ;
+ cfun->machine->base_reg =
+ gen_rtx_REG (Pmode, (br > 0) ? br : BASE_REGNUM);
+ }
s390_register_info ();
s390_frame_info ();
--
2.3.0
