Use dwarf assembler in gdb.dwarf2/implptr-64bit.exp

This patch adds a DW_OP_implicit_value in dwarf assembler, and uses
dwarf assembler in implptr-64bit.exp.  Using dwarf assembler in
implptr-64bit.exp exposes some limitations in dwarf assembler,

 - some variables are not evaluated in the caller's context, so we
   can not pass variable to assembler, like this

       Dwarf::assemble $asm_file {

	cu {
	    version $dwarf_version
	    addr_size $addr_size
	    is_64 $is_64
	} {
	}

	and

	{DW_AT_type :$struct_label "DW_FORM_ref$ref_addr_size"}

   this limitation is fixed by adding "uplevel" and "subst".

 - dwarf assembler doesn't emit DW_FORM_ref_addr for label referencing.
   this limitation is fixed by adding a new character "%",

	{ type %$int_label }

   this means we want to emit DW_FORM_ref_addr for label referencing.

 - we can't set the form of label referencing offset in dwarf assembler.
   Nowadays, dwarf assembler guesses the form of labels, which is
   DW_FORM_ref4.  However, in implptr-64bit.exp, both DW_FORM_ref4
   and DW_FORM_ref8 is used (see REF_ADDR in implptr-64bit.S).  This
   patch adds the flexibility of setting the form of label reference.
   Both of them below are valid,

	{DW_AT_type :$struct_label}
	{DW_AT_type :$struct_label DW_FORM_ref8}

   the former form is the default DW_FORM_ref4.

I compared the .debug_info of objects without and with this patch
applied.  There is no changes except abbrev numbers.

gdb/testsuite:

2017-01-25  Andreas Arnez  <arnez@linux.vnet.ibm.com>
	    Yao Qi  <yao.qi@linaro.org>

	* gdb.dwarf2/implptr-64bit.exp: Use dwarf assembler.
	* gdb.dwarf2/implptr-64bit.S: Remove.
	* lib/dwarf.exp (Dwarf): Handle character "%".  Evaluate some
	variables in caller's context.  Add DW_OP_implicit_value.

1 files changed, 109 insertions, 9 deletions

diff --git a/gdb/testsuite/gdb.dwarf2/implptr-64bit.exp b/gdb/testsuite/gdb.dwarf2/implptr-64bit.exp
index b4dcbdeb802..963cdc68ef2 100644
--- a/gdb/testsuite/gdb.dwarf2/implptr-64bit.exp
+++ b/gdb/testsuite/gdb.dwarf2/implptr-64bit.exp
@@ -19,21 +19,121 @@ if {![dwarf2_support]} {
     return 0  
 }
 
-standard_testfile .S
-set mainfile main.c
+standard_testfile main.c
 
 proc test { dwarf_version offset_size addr_size ref_addr_size two_cu } {
-    global testfile srcfile mainfile
+    global testfile srcfile
 
-    # 32-bit targets do not support any of the testcases; keep quiet there.
-    set opts {quiet}
-    foreach n { dwarf_version offset_size addr_size ref_addr_size two_cu } {
-	lappend opts "additional_flags=-D[string toupper $n]=[expr "\$$n"]"
+    set name "d${dwarf_version}o${offset_size}a${addr_size}r${ref_addr_size}t${two_cu}"
+
+    # Make some DWARF for the test.
+    set asm_file [standard_output_file ${testfile}-${name}.S]
+    Dwarf::assemble $asm_file {
+	upvar dwarf_version dwarf_version
+	upvar addr_size addr_size
+	upvar offset_size offset_size
+	upvar ref_addr_size ref_addr_size
+	upvar two_cu two_cu
+
+	set is_64 [expr { $offset_size == 4 ? 0 : 1 }]
+
+	cu {
+	    version $dwarf_version
+	    addr_size $addr_size
+	    is_64 $is_64
+	} {
+	    compile_unit {
+		{ producer "GNU C 4.4.3" }
+		{ language @DW_LANG_C89 }
+		{ name 1.c }
+	    } {
+		declare_labels struct_label variable_label int_label pointer_label
+
+		int_label: base_type {
+		    { byte_size 4 DW_FORM_sdata }
+		    { DW_AT_encoding @DW_ATE_signed }
+		    { name int }
+		}
+
+		struct_label: structure_type {
+		    { name s }
+		    { byte_size 4 sdata }
+		} {
+		    member {
+			{ name f }
+			{ type :$int_label }
+			{ data_member_location 0 data1 }
+		    }
+		}
+
+		pointer_label: pointer_type {
+		    { byte_size $Dwarf::_cu_addr_size sdata }
+		    { type  :$struct_label }
+		}
+
+		variable_label: DW_TAG_variable {
+		    { name v }
+		    { location {
+			DW_OP_implicit_value 0x1 0x1 0x1 0x1
+		    } SPECIAL_expr}
+		    { type :$struct_label "DW_FORM_ref$ref_addr_size" }
+		}
+
+		if { !$two_cu } {
+		    subprogram {
+			{ name main }
+			{ low_pc main addr }
+			{ high_pc "main+0x100" addr }
+			{ type %$int_label }
+			{ external 1 flag }
+		    } {
+			DW_TAG_variable {
+			    { name p }
+			    { location {
+				GNU_implicit_pointer $variable_label 0
+			    } SPECIAL_expr }
+			    { type :$pointer_label "DW_FORM_ref$ref_addr_size" }
+			}
+		    }
+		}
+	    }
+	}
+
+	if { $two_cu } {
+	    cu {
+		version $dwarf_version
+		addr_size $addr_size
+		is_64 $is_64
+	    } {
+		compile_unit {
+		    { producer "GNU C 4.4.3" }
+		    { language @DW_LANG_C89 }
+		    { name 1.c }
+		} {
+		    subprogram {
+			{ name main }
+			{ low_pc main addr }
+			{ high_pc "main+0x100" addr }
+			{ type %$int_label }
+			{ external 1 flag }
+		    } {
+			DW_TAG_variable {
+			    { name p }
+			    { location {
+				GNU_implicit_pointer $variable_label 0
+			    } SPECIAL_expr }
+			    { type %$pointer_label }
+			}
+		    }
+		}
+	    }
+	}
     }
 
-    set name "d${dwarf_version}o${offset_size}a${addr_size}r${ref_addr_size}t${two_cu}"
+    # 32-bit targets do not support any of the testcases; keep quiet there.
+    set opts {quiet}
     set executable ${testfile}-${name}
-    if [prepare_for_testing "failed to prepare" $executable "${srcfile} ${mainfile}" $opts] {
+    if [prepare_for_testing "failed to prepare" $executable "${asm_file} ${srcfile}" $opts] {
 	return -1
     }