diff mbox series

xtensa: Make register A0 allocable for the CALL0 ABI

Message ID faee7f9c-aef5-33e7-5f22-a52464ee4c35@yahoo.co.jp
State New
Headers
Series xtensa: Make register A0 allocable for the CALL0 ABI |

Commit Message

Takayuki 'January June' Suwa Oct. 21, 2022, 2:58 a.m. UTC 
  This patch offers an additional allocable register by RA for the CALL0
ABI.

> Register a0 holds the return address upon entry to a function, but
> unlike the windowed register ABI, it is not reserved for this purpose
> and may hold other values after the return address has been saved.
  - Xtensa ISA Reference Manual,
                   8.1.2 "CALL0 Register Usage and Stack Layout" [p.589]

gcc/ChangeLog:

	* config/xtensa/xtensa.cc (xtensa_conditional_register_usage):
	Remove register A0 from FIXED_REGS if the CALL0 ABI.
---
 gcc/config/xtensa/xtensa.cc | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

Max Filippov Oct. 21, 2022, 5:49 a.m. UTC | #1 
Hi Suwa-san,

On Thu, Oct 20, 2022 at 7:58 PM Takayuki 'January June' Suwa
<jjsuwa_sys3175@yahoo.co.jp> wrote:
>
> This patch offers an additional allocable register by RA for the CALL0
> ABI.
>
> > Register a0 holds the return address upon entry to a function, but
> > unlike the windowed register ABI, it is not reserved for this purpose
> > and may hold other values after the return address has been saved.
>   - Xtensa ISA Reference Manual,
>                    8.1.2 "CALL0 Register Usage and Stack Layout" [p.589]
>
> gcc/ChangeLog:
>
>         * config/xtensa/xtensa.cc (xtensa_conditional_register_usage):
>         Remove register A0 from FIXED_REGS if the CALL0 ABI.
> ---
>  gcc/config/xtensa/xtensa.cc | 7 +++++++
>  1 file changed, 7 insertions(+)

This change results in the following new regressions:

FAIL: gcc.c-torture/execute/20040709-1.c   -O3 -fomit-frame-pointer
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution
test
FAIL: gcc.c-torture/execute/20040709-2.c   -O3 -fomit-frame-pointer
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution
test
FAIL: gcc.c-torture/execute/20190820-1.c   -O3 -fomit-frame-pointer
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution
test
FAIL: gcc.c-torture/execute/loop-15.c   -O3 -fomit-frame-pointer
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution
test
FAIL: gcc.dg/torture/pr101031.c   -O3 -fomit-frame-pointer
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution
test
FAIL: gcc.dg/torture/pr101972.c   -O3 -fomit-frame-pointer
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution
test
FAIL: gcc.dg/torture/pr99954.c   -O3 -fomit-frame-pointer
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution
test
FAIL: g++.dg/coroutines/torture/co-yield-04-complex-local-state.C
-O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer
-finline-functions  execution test
FAIL: g++.dg/coroutines/torture/local-var-05-awaitable.C   -O3
-fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer
-finline-functions  execution test
diff mbox series

Patch

diff --git a/gcc/config/xtensa/xtensa.cc b/gcc/config/xtensa/xtensa.cc
index 950eb5a59be..f30725113dc 100644
--- a/gcc/config/xtensa/xtensa.cc
+++ b/gcc/config/xtensa/xtensa.cc
@@ -4970,6 +4970,13 @@  xtensa_conditional_register_usage (void)
   /* Remove hard FP register from the preferred reload registers set.  */
   CLEAR_HARD_REG_BIT (reg_class_contents[(int)RL_REGS],
 		      HARD_FRAME_POINTER_REGNUM);
+
+  /* Register A0 holds the return address upon entry to a function
+     for the CALL0 ABI, but unlike the windowed register ABI, it is
+     not reserved for this purpose and may hold other values after
+     the return address has been saved.  */
+  if (!TARGET_WINDOWED_ABI)
+    fixed_regs[A0_REG] = 0;
 }
 
 /* Map hard register number to register class */