Power10 pc-relative code doesn't use or preserve r2 as a TOC pointer.
That means calling between pc-relative and TOC using code can't be
done without intervening linker stubs, and a call from TOC code to
pc-relative code must have a nop after the bl in order to restore r2.
Now the PowerPC libffi assembly code doesn't use r2 except for the
implicit use when making calls back to C, ffi_closure_helper_LINUX64
and ffi_prep_args64. So changing the assembly to interoperate with
pc-relative code without stubs is easily done. Controlling that is a
new built-in macro.
Upstream libffi currently has a different patch applied to work around
the power10 build failure. I'll post a delta for upstream.
Bootstrapped and regression tested on power8, built for power10.
gcc/
* config/rs6000/rs6000-c.c (rs6000_target_modify_macros):
Conditionally define __PCREL__.
libffi/
* src/powerpc/linux64.S (ffi_call_LINUX64): Don't emit global
entry when __PCREL__. Call using @notoc.
(ffi_closure_LINUX64, ffi_go_closure_linux64): Likewise.
diff --git a/gcc/config/rs6000/rs6000-c.c b/gcc/config/rs6000/rs6000-c.c
index f5982907e90..cc1e997524e 100644
--- a/gcc/config/rs6000/rs6000-c.c
+++ b/gcc/config/rs6000/rs6000-c.c
@@ -597,6 +597,9 @@ rs6000_target_modify_macros (bool define_p, HOST_WIDE_INT
flags,
/* Tell the user if we support the MMA instructions. */
if ((flags & OPTION_MASK_MMA) != 0)
rs6000_define_or_undefine_macro (define_p, "__MMA__");
+ /* Whether pc-relative code is being generated. */
+ if ((flags & OPTION_MASK_PCREL) != 0)
+ rs6000_define_or_undefine_macro (define_p, "__PCREL__");
}
void
diff --git a/libffi/src/powerpc/linux64.S b/libffi/src/powerpc/linux64.S
index b2ae60ead6e..bfb4d2957ae 100644
--- a/libffi/src/powerpc/linux64.S
+++ b/libffi/src/powerpc/linux64.S
@@ -36,8 +36,10 @@
.cfi_startproc
# if _CALL_ELF == 2
ffi_call_LINUX64:
+# ifndef __PCREL__
addis %r2, %r12, .TOC.-ffi_call_LINUX64@ha
addi %r2, %r2, .TOC.-ffi_call_LINUX64@l
+# endif
.localentry ffi_call_LINUX64, . - ffi_call_LINUX64
# else
.section ".opd","aw"
@@ -89,7 +91,11 @@ ffi_call_LINUX64:
/* Call ffi_prep_args64. */
mr %r4, %r1
# if defined _CALL_LINUX || _CALL_ELF == 2
+# ifdef __PCREL__
+ bl ffi_prep_args64@notoc
+# else
bl ffi_prep_args64
+# endif
# else
bl .ffi_prep_args64
# endif
diff --git a/libffi/src/powerpc/linux64_closure.S
b/libffi/src/powerpc/linux64_closure.S
index 6487d2a2970..938e86034f1 100644
--- a/libffi/src/powerpc/linux64_closure.S
+++ b/libffi/src/powerpc/linux64_closure.S
@@ -37,8 +37,10 @@
.cfi_startproc
# if _CALL_ELF == 2
ffi_closure_LINUX64:
+# ifndef __PCREL__
addis %r2, %r12, .TOC.-ffi_closure_LINUX64@ha
addi %r2, %r2, .TOC.-ffi_closure_LINUX64@l
+# endif
.localentry ffi_closure_LINUX64, . - ffi_closure_LINUX64
# else
.section ".opd","aw"
@@ -155,7 +157,11 @@ ffi_closure_LINUX64:
# make the call
# if defined _CALL_LINUX || _CALL_ELF == 2
+# ifdef __PCREL__
+ bl ffi_closure_helper_LINUX64@notoc
+# else
bl ffi_closure_helper_LINUX64
+# endif
# else
bl .ffi_closure_helper_LINUX64
# endif
@@ -396,8 +402,10 @@ ffi_closure_LINUX64:
.cfi_startproc
# if _CALL_ELF == 2
ffi_go_closure_linux64:
+# ifndef __PCREL__
addis %r2, %r12, .TOC.-ffi_go_closure_linux64@ha
addi %r2, %r2, .TOC.-ffi_go_closure_linux64@l
+# endif
.localentry ffi_go_closure_linux64, . - ffi_go_closure_linux64
# else
.section ".opd","aw"
--
Alan Modra
Australia Development Lab, IBM
