[PATCH 4/4] s390: Use pc-relative insns in 31-bit mode

[Richard Henderson <rth@twiddle.net>]

From: Richard Henderson <rth@redhat.com>

It's silly to stick to esa/390 features when the compiler won't.
Detect when brasl and larl are used by the compiler and then use
them in the assembly.
---
 configure.ac    | 17 +++++++++++++++++
 src/s390/sysv.S | 19 +++++++++++++++++--
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index d5414f9..2941cd7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -183,6 +183,23 @@ if test x$TARGET = xX86 || test x$TARGET = xX86_WIN32 || test x$TARGET = xX86_64
     fi
 fi
 
+if test x$TARGET = xS390; then
+    AC_CACHE_CHECK([compiler uses zarch features],
+	libffi_cv_as_s390_zarch, [
+	libffi_cv_as_s390_zarch=no
+	echo 'void foo(void) { bar(); bar(); }' > conftest.c
+	if $CC $CFLAGS -S conftest.c > /dev/null 2>&1; then
+	    if grep -q brasl conftest.s; then
+	        libffi_cv_as_s390_zarch=yes
+	    fi
+	fi
+	])
+    if test "x$libffi_cv_as_s390_zarch" = xyes; then
+	AC_DEFINE(HAVE_AS_S390_ZARCH, 1,
+		  [Define if the compiler uses zarch features.])
+    fi
+fi
+
 # On PaX enable kernels that have MPROTECT enable we can't use PROT_EXEC.
 AC_ARG_ENABLE(pax_emutramp,
   [  --enable-pax_emutramp       enable pax emulated trampolines, for we can't use PROT_EXEC],
diff --git a/src/s390/sysv.S b/src/s390/sysv.S
index df9083e..1869269 100644
--- a/src/s390/sysv.S
+++ b/src/s390/sysv.S
@@ -55,13 +55,21 @@ ffi_call_SYSV:
 	.cfi_rel_offset r14, 56
 	.cfi_def_cfa_register r13
 	l	%r15,60(%r2)			# Set up outgoing stack
+#ifdef HAVE_AS_S390_ZARCH
+	larl	%r14,.Ltable
+#else
 	basr	%r14,0				# Set up base register
 .Lbase:
+#endif
 	sla	%r3,3				# ret_type *= 8
 	lr	%r12,%r4			# Save ret_addr
 	lr	%r1,%r5				# Save fun
 	lr	%r0,%r6				# Install static chain
+#ifdef HAVE_AS_S390_ZARCH
+	la	%r14,0(%r14,%r3)		# Set return address
+#else
 	la	%r14,.Ltable-.Lbase(%r14,%r3)	# Set return address
+#endif
 	lm	%r2,%r6,8(%r13)			# Load arguments
 	ld	%f0,64(%r13)
 	ld	%f2,72(%r13)
@@ -141,10 +149,12 @@ ffi_closure_SYSV:
 	.cfi_rel_offset r13, 52
 	.cfi_rel_offset r14, 56
 	.cfi_rel_offset r15, 60
+#ifndef HAVE_AS_S390_ZARCH
 	basr	%r13,0				# Set up base register
 .Lcbase:
-	ahi	%r15,-96-8			# Set up stack frame
 	l	%r1,.Lchelper-.Lcbase(%r13)	# Get helper function
+#endif
+	ahi	%r15,-96-8			# Set up stack frame
 	st	%r12,0(%r15)			# Set up back chain
 
 	std	%f0,64(%r12)			# Save fp arguments
@@ -154,7 +164,11 @@ ffi_closure_SYSV:
 	st	%r5,96(%r15)
 	la	%r6,64(%r12)			# FPRs
 	la	%r5,8(%r12)			# GPRs
+#ifdef HAVE_AS_S390_ZARCH
+	brasl	%r14,ffi_closure_helper_SYSV
+#else
 	bas	%r14,0(%r1,%r13)		# Call helper
+#endif
 
 	lr	%r15,%r12
 	.cfi_def_cfa_register r15
@@ -165,10 +179,11 @@ ffi_closure_SYSV:
 	br	%r14
 	.cfi_endproc
 
+#ifndef HAVE_AS_S390_ZARCH
 	.align 4
 .Lchelper:
 	.long	ffi_closure_helper_SYSV-.Lcbase
-
+#endif
 
 	.size	 ffi_closure_SYSV,.-ffi_closure_SYSV
 
-- 
2.1.0