Get start and end address of main in dwz.exp

On arm-none-eabi target thumb mode, I see the following fail,

p the_int^M
$2 = 99^M
(gdb) FAIL: gdb.dwarf2/dwz.exp: p the_int

and on powerpc64 target, we even can't get function main from object
file,

disassemble main^M
No function contains specified address.^M
(gdb) FAIL: gdb.dwarf2/dwz.exp: disassemble main

This patch is to use MACRO_AT_func attribute to get the main's start
address and end address correctly, and also remove some code dwz.exp
getting main's length.  This patch fixes fails on both thumb mode and
powerpc64 target.

PASS: gdb.dwarf2/dwz.exp: p other_int
PASS: gdb.dwarf2/dwz.exp: p the_int

gdb/testsuite:

2014-11-14  Yao Qi  <yao@codesourcery.com>

	* gdb.dwarf2/dwz.exp: Remove the code to compile main.c to
	object and get function length.
	(Dwarf::assemble): Replace name, low_pc and high_pc attributes
	with MACRO_AT_func.
	(top-level): Replace gdb_compile and clean_restart with
	prepare_for_testing.
	* gdb.dwarf2/main.c (main): Add label main_label.

3 files changed, 14 insertions, 57 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 59fd16e..5e9b9df 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,15 @@
 2014-11-14  Yao Qi  <yao@codesourcery.com>
 
+	* gdb.dwarf2/dwz.exp: Remove the code to compile main.c to
+	object and get function length.
+	(Dwarf::assemble): Replace name, low_pc and high_pc attributes
+	with MACRO_AT_func.
+	(top-level): Replace gdb_compile and clean_restart with
+	prepare_for_testing.
+	* gdb.dwarf2/main.c (main): Add label main_label.
+
+2014-11-14  Yao Qi  <yao@codesourcery.com>
+
 	* lib/dwarf.exp (function_range): New procedure.
 	(Dwarf::_handle_macro_at_func): New procedure.
 	(Dwarf::_handle_macro_at_range): New procedure.
diff --git a/gdb/testsuite/gdb.dwarf2/dwz.exp b/gdb/testsuite/gdb.dwarf2/dwz.exp
index 9175f9e..c7ecc2b 100644
--- a/gdb/testsuite/gdb.dwarf2/dwz.exp
+++ b/gdb/testsuite/gdb.dwarf2/dwz.exp
@@ -22,65 +22,18 @@ if {![dwarf2_support]} {
 
 standard_testfile main.c dwz.S
 
-if  {[gdb_compile ${srcdir}/${subdir}/${srcfile} ${binfile}1.o \
-	  object {nodebug}] != ""} {
-    return -1
-}
-
-# Start GDB and load object file, compute the function length which is
-# needed in the Dwarf Assembler below.
-clean_restart ${testfile}1.o
-
-set main_length ""
-set test "disassemble main"
-gdb_test_multiple $test $test {
-    -re ".*$hex <\\+($decimal)>:\[^\r\n\]+\r\nEnd of assembler dump\.\r\n$gdb_prompt $" {
-	set main_length $expect_out(1,string)
-	pass $test
-    }
-}
-
-if { $main_length == "" } {
-    # Bail out here, because we can't do the following tests if
-    # $main_length is unknown.
-    return -1
-}
-
-# Compute the size of the last instruction.
-
-set test "x/2i main+$main_length"
-gdb_test_multiple $test $test {
-    -re ".*($hex) <main\\+$main_length>:\[^\r\n\]+\r\n\[ \]+($hex).*\.\r\n$gdb_prompt $" {
-	set start $expect_out(1,string)
-	set end $expect_out(2,string)
-
-	set main_length [expr $main_length + $end - $start]
-	pass $test
-    }
-}
-
-if { $main_length == "" } {
-    # Bail out here, because we can't do the following tests if
-    # $main_length is unknown.
-    return -1
-}
-
-gdb_exit
-
 # Create the DWARF.
 set asm_file [standard_output_file $srcfile2]
 Dwarf::assemble $asm_file {
     declare_labels partial_label int_label int_label2
-    global main_length
+    global srcdir subdir srcfile
 
     extern main
 
     cu {} {
 	partial_label: partial_unit {} {
 	    subprogram {
-		{name main}
-		{low_pc main addr}
-		{high_pc "main + $main_length" addr}
+ 		{MACRO_AT_func { main ${srcdir}/${subdir}/${srcfile} }}
 	    }
 	}
     }
@@ -128,17 +81,10 @@ Dwarf::assemble $asm_file {
     }
 }
 
-if  {[gdb_compile $asm_file ${binfile}2.o object {nodebug}] != ""} {
+if [prepare_for_testing ${testfile}.exp $testfile "${asm_file} ${srcfile}" {}] {
     return -1
 }
 
-if  {[gdb_compile [list ${binfile}1.o ${binfile}2.o] \
-	  "${binfile}" executable {}] != ""} {
-    return -1
-}
-
-clean_restart ${testfile}
-
 if ![runto_main] {
     return -1
 }
diff --git a/gdb/testsuite/gdb.dwarf2/main.c b/gdb/testsuite/gdb.dwarf2/main.c
index 3ddd194..e6d4715 100644
--- a/gdb/testsuite/gdb.dwarf2/main.c
+++ b/gdb/testsuite/gdb.dwarf2/main.c
@@ -20,5 +20,6 @@
 int
 main()
 {
+  asm ("main_label: .globl main_label");
   return 0;
 }