From cba8a572c208078c1c6eb9845b54f960526c53c0 Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <ian@gcc.gnu.org>
Date: Wed, 27 Feb 2019 22:35:10 +0000
Subject: re PR go/89172 (FAIL: runtime/pprof)

	PR go/89172
    internal/cpu, runtime, runtime/pprof: handle function descriptors

    When using PPC64 ELF ABI v1 a function address is not a PC, but is the
    address of a function descriptor.  The first field in the function
    descriptor is the actual PC (see
    http://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html#FUNC-DES).
    The libbacktrace library knows about this, and libgo uses actual PC
    values consistently except for the helper function funcPC that appears
    in both runtime and runtime/pprof.

    This patch fixes funcPC by recording, in the internal/cpu package,
    whether function descriptors are being used.  We have to check for
    function descriptors using a C compiler check, because GCC can be
    configured using --with-abi to select the ELF ABI to use.

    Fixes https://gcc.gnu.org/PR89172

    Reviewed-on: https://go-review.googlesource.com/c/162978

From-SVN: r269266
---
 libgo/configure | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

(limited to 'libgo/configure')

diff --git a/libgo/configure b/libgo/configure
index 0b8ebce..06b68b0 100755
--- a/libgo/configure
+++ b/libgo/configure
@@ -661,6 +661,7 @@ GO_SYSCALL_OS_ARCH_FILE
 GO_SYSCALL_OS_FILE
 GO_LIBCALL_OS_ARCH_FILE
 GO_LIBCALL_OS_FILE
+FUNCTION_DESCRIPTORS
 ALLGOARCHFAMILY
 ALLGOARCH
 GOARCH
@@ -11343,7 +11344,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11346 "configure"
+#line 11347 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11449,7 +11450,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11452 "configure"
+#line 11453 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -14088,6 +14089,27 @@ esac
 
 
 
+FUNCTION_DESCRIPTORS=false
+case ${host} in
+  rs6000*-*-* | powerpc*-*-*)
+    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#if _CALL_ELF == 1
+#error descriptors
+#endif
+
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  FUNCTION_DESCRIPTORS=false
+else
+  FUNCTION_DESCRIPTORS=true
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+    ;;
+esac
+
+
 GO_LIBCALL_OS_FILE=
 GO_LIBCALL_OS_ARCH_FILE=
 GO_SYSCALL_OS_FILE=
-- 
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