Maciej W. Rozycki macro@codesourcery.com
Fri Oct 29 14:40:00 GMT 2010

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---

Hi,

 There are several cases where ELF symbol attributes are not correctly set 
for symbols leading to all kinds of odd side effects for MIPS16 code (and 
with the upcoming change also for microMIPS code).

 For example this program:

	.text
foo:
	xor	$16, $17
	.set	fnord, . + 2
	addu	$2, $3, $4
	xor	$5, $6
bar:
	subu	$7, $16

assembles to this:

Disassembly of section .text:

00000000 <foo>:
   0:	e82e     	xor	s0,s1
   2:	e389     	addu	v0,v1,a0

00000004 <fnord>:
   4:	edcee71f 	swc3	$14,-6369(t6)

00000006 <bar>:
   6:	e71f     	subu	a3,s0

Notice how fnord's ELF attributes have not been set to indicate a MIPS16 
symbol and the resulting confusion (this symbol, of course, if used as a 
jump target will not set the ISA bit correctly).  Similar symptoms are 
seen with equated symbols (defined with .eqv) although the attributes are 
lost at a different stage of assembly.

 Here's a fix for these problems and a test case covering hopefully most 
of them as well as those fixed by patches submitted previously in this series.

 There are two new functions defined:

- mips_elf_copy_symbol_attributes() -- used for symbols defined with .set.  
  These, if calculated from a label that has been defined for the current 
  location (the "dot" special symbol being a prominent example, but any 
  label will actually do) will not have their ELF attributes set, because 
  the original label will only get them set once an instruction has been 
  emitted.  A solution is to place the newly defined symbol on the list of 
  labels too.

- mips_elf_propagate_symbol_attributes() -- used for symbols defined with 
  .eqv.  They are processed late and currently attributes are copied only 
  for exact copies of other symbols, i.e.:

	.eqv	foo, bar

  but not:

	.eqv	foo, bar + 2

  In the case of MIPS16 (and microMIPS) ELF attribute we want it to be 
  propagated even for offsetted symbols, hence the new hook in 
  resolve_symbol_value().

 Finally I realised the uniqueness of the -mmips:16 option to `objdump' 
that causes all the disassembled to be treated as MIPS16 code, regardless 
of symbol annotations found.  This actually covers the bugs addressed 
here, hence I'm removing it.  The implication is all MIPS16 tests need to 
have a label at the beginning to set the ISA mode of the disassembler 
correctly.

 Perhaps the behaviour of the -mmips:16 option should be changed instead 
so that it respects symbol annotations.  I think it would make sense -- 
the option should normally only be needed for binary objects with no 
sufficient symbol information.  OTOH, the current behaviour is good in 
case `objdump' gets confused because of a bug or a broken binary, hence I 
have no strong preference actually towards making the change.

 If we agree to make it after all, then the option can be added back.  I 
believe -mmips:micromips behaves the same.  Additionally odd text symbols 
with no ELF annotation are unconditionally treated as MIPS16 code.  This 
should probably be changed.

 Compared to the original version, this change has only been trivially 
updated to take the new treatment of symbols equated to an expression 
involving "." into account.  The update is limited to the test case 
according to the comment I'll just repeat here: "Move the location counter 
away from the end of code to avoid the final values of symbols equated to 
expressions involving the counter interfering with disassembly."  Without 
this change MIPS16 code would be disassembled incorrectly as the equated 
symbols have the MIPS16 attribute clear (quite correctly, because the 
final value of "." does not point to MIPS16 code).  Dumps have been 
adjusted accordingly.

2010-10-29  Maciej W. Rozycki  <macro@codesourcery.com>

 	gas/
	* config/tc-mips.c (insn_label_recording): New variable.
	(md_begin): Set insn_label_recording.
	(md_mips_end): Clear insn_label_recording.
	(mips_elf_copy_symbol_attributes): New function.
	(mips_elf_propagate_symbol_attributes): New function.
	* config/tc-mips.h (TC_COPY_SYMBOL_ATTRIBUTES): New macro.
	(TC_PROPAGATE_SYMBOL_ATTRIBUTES): Likewise.
	(mips_elf_copy_symbol_attributes): New prototype.
	(mips_elf_propagate_symbol_attributes): Likewise.
	* symbols.c (resolve_symbol_value): Call 
	TC_PROPAGATE_SYMBOL_ATTRIBUTES for symbols that are not exact
	copies of originals.

	gas/testsuite/
	* gas/mips/branch-self.d: New test for various definitions of 
	labels.
	* gas/mips/branch-self.s: Source for the new test.
	* gas/mips/mips.exp: Run the new test.  Remove -mmips:16 from
	"mips16" architecture.

 OK to apply?

  Maciej

binutils-gas-propagate-attrs.diff
Index: binutils-fsf-trunk-quilt/gas/config/tc-mips.c
===================================================================
--- binutils-fsf-trunk-quilt.orig/gas/config/tc-mips.c	2010-10-29 09:07:10.000000000 +0100
+++ binutils-fsf-trunk-quilt/gas/config/tc-mips.c	2010-10-29 09:07:11.000000000 +0100
@@ -1256,6 +1256,8 @@ struct insn_label_list
 static struct insn_label_list *free_insn_labels;
 #define label_list tc_segment_info_data.labels
 
+static int insn_label_recording;
+
 static void mips_clear_insn_labels (void);
 
 static inline void
@@ -2095,11 +2097,15 @@ md_begin (void)
 
   if (mips_fix_vr4120)
     init_vr4120_conflicts ();
+
+  insn_label_recording = 1;
 }
 
 void
 md_mips_end (void)
 {
+  insn_label_recording = 0;
+
   if (! ECOFF_DEBUGGING)
     md_obj_end ();
 }
@@ -14726,9 +14732,38 @@ mips_symbol_new_hook (symbolS *sym)
       && S_GET_VALUE (sym) == frag_now_fix ())
     mips_record_label (sym);
 }
-
+
 #if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
 
+/* Record copies of instruction labels made, for later MIPS16 symbol
+   annotation.  */
+
+void
+mips_elf_copy_symbol_attributes (symbolS *dest, symbolS *src ATTRIBUTE_UNUSED)
+{
+  if (!IS_ELF || !insn_label_recording)
+    return;
+
+  if (S_GET_SEGMENT (src) == now_seg
+      && symbol_get_frag (src) == frag_now
+      && symbol_constant_p (src)
+      && S_GET_VALUE (src) == frag_now_fix ()
+      && symbol_constant_p (dest))
+    mips_record_label (dest);
+}
+
+/* Propagate MIPS16 symbol annotation.  */
+
+void
+mips_elf_propagate_symbol_attributes (symbolS *dest, symbolS *src)
+{
+  if (!IS_ELF)
+    return;
+
+  if (ELF_ST_IS_MIPS16 (S_GET_OTHER (src)))
+    S_SET_OTHER (dest, ELF_ST_SET_MIPS16 (S_GET_OTHER (dest)));
+}
+
 /* Some special processing for a MIPS ELF file.  */
 
 void
Index: binutils-fsf-trunk-quilt/gas/config/tc-mips.h
===================================================================
--- binutils-fsf-trunk-quilt.orig/gas/config/tc-mips.h	2010-10-29 09:07:10.000000000 +0100
+++ binutils-fsf-trunk-quilt/gas/config/tc-mips.h	2010-10-29 09:07:11.000000000 +0100
@@ -121,6 +121,14 @@ extern void mips_frob_file (void);
 #if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
 #define tc_frob_file_after_relocs mips_frob_file_after_relocs
 extern void mips_frob_file_after_relocs (void);
+
+#define TC_COPY_SYMBOL_ATTRIBUTES(dest, src) \
+  mips_elf_copy_symbol_attributes (dest, src)
+extern void mips_elf_copy_symbol_attributes (symbolS *, symbolS *);
+
+#define TC_PROPAGATE_SYMBOL_ATTRIBUTES(dest, src) \
+  mips_elf_propagate_symbol_attributes (dest, src)
+extern void mips_elf_propagate_symbol_attributes (symbolS *, symbolS *);
 #endif
 
 #define tc_fix_adjustable(fixp) mips_fix_adjustable (fixp)
Index: binutils-fsf-trunk-quilt/gas/symbols.c
===================================================================
--- binutils-fsf-trunk-quilt.orig/gas/symbols.c	2010-10-29 09:07:10.000000000 +0100
+++ binutils-fsf-trunk-quilt/gas/symbols.c	2010-10-29 09:07:11.000000000 +0100
@@ -1176,12 +1176,19 @@ resolve_symbol_value (symbolS *symp)
 	      break;
 	    }
 
-	  if (finalize_syms && final_val == 0)
+	  if (finalize_syms)
 	    {
-	      if (LOCAL_SYMBOL_CHECK (add_symbol))
-		add_symbol = local_symbol_convert ((struct local_symbol *)
-						   add_symbol);
-	      copy_symbol_attributes (symp, add_symbol);
+	      if (final_val == 0)
+		{
+		  if (LOCAL_SYMBOL_CHECK (add_symbol))
+		    add_symbol = local_symbol_convert ((struct local_symbol *)
+						       add_symbol);
+		  copy_symbol_attributes (symp, add_symbol);
+		}
+#ifdef TC_PROPAGATE_SYMBOL_ATTRIBUTES
+	      else
+		TC_PROPAGATE_SYMBOL_ATTRIBUTES (symp, add_symbol);
+#endif
 	    }
 
 	  /* If we have equated this symbol to an undefined or common
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/branch-self.d
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/branch-self.d	2010-10-29 09:07:11.000000000 +0100
@@ -0,0 +1,30 @@
+#objdump: -dr --prefix-addresses --show-raw-insn
+#name: MIPS branches to self
+#as: -32
+#source: branch-self.s
+
+# Test various ways to request a branch to self.
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+([0-9a-f]+) <[^>]*> ac620000 	sw	v0,0\(v1\)
+([0-9a-f]+) <[^>]*> 1000ffff 	b	\1 <.*>
+([0-9a-f]+) <[^>]*> 00000000 	nop
+([0-9a-f]+) <[^>]*> ac620000 	sw	v0,0\(v1\)
+([0-9a-f]+) <[^>]*> 1000ffff 	b	\1 <.*>
+([0-9a-f]+) <[^>]*> 00000000 	nop
+([0-9a-f]+) <[^>]*> ac620000 	sw	v0,0\(v1\)
+([0-9a-f]+) <[^>]*> 1000ffff 	b	\1 <.*>
+([0-9a-f]+) <[^>]*> 00000000 	nop
+([0-9a-f]+) <[^>]*> ac620000 	sw	v0,0\(v1\)
+([0-9a-f]+) <[^>]*> 1000ffff 	b	\1 <.*>
+([0-9a-f]+) <[^>]*> 00000000 	nop
+([0-9a-f]+) <[^>]*> ac620000 	sw	v0,0\(v1\)
+([0-9a-f]+) <[^>]*> 1000ffff 	b	\1 <.*>
+([0-9a-f]+) <[^>]*> 00000000 	nop
+([0-9a-f]+) <[^>]*> ac620000 	sw	v0,0\(v1\)
+([0-9a-f]+) <[^>]*> 1000ffff 	b	\1 <.*>
+([0-9a-f]+) <[^>]*> 00000000 	nop
+	\.\.\.
+	\.\.\.
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/branch-self.s
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/branch-self.s	2010-10-29 09:07:11.000000000 +0100
@@ -0,0 +1,35 @@
+# Source file used to test branches to self.
+	.text
+foo:
+	sw	$2, ($3)
+	b	.
+
+	sw	$2, ($3)
+0:
+	b	0b
+
+	sw	$2, ($3)
+bar:
+	b	bar
+
+	sw	$2, ($3)
+	.set	frob, .
+	b	frob
+
+	.eqv	fnord, .
+	sw	$2, ($3)
+	b	fnord
+
+	.eqv	foobar, fnord + 4
+	.eqv	foobaz, foobar - 16
+	sw	$2, ($3)
+	b	foobaz + 12
+
+# Move the location counter away from the end of code to avoid the final
+# values of symbols equated to expressions involving the counter interfering
+# with disassembly.
+	.space	16
+
+# Force at least 8 (non-delay-slot) zero bytes, to make 'objdump' print ...
+	.align	2
+	.space	8
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/mips.exp
===================================================================
--- binutils-fsf-trunk-quilt.orig/gas/testsuite/gas/mips/mips.exp	2010-10-29 09:07:06.000000000 +0100
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/mips.exp	2010-10-29 09:07:11.000000000 +0100
@@ -390,7 +390,7 @@ mips_arch_create mips64r2 64	mips64	{ mi
 			{ -mmips:isa64r2 } \
 			{ mipsisa64r2-*-* mipsisa64r2el-*-* }
 mips_arch_create mips16	32	{}	{} \
-			{ -march=mips1 -mips16 } { -mmips:16 }
+			{ -march=mips1 -mips16 } {}
 mips_arch_create r3000 	32	mips1	{} \
 			{ -march=r3000 -mtune=r3000 } { -mmips:3000 }
 mips_arch_create r3900 	32	mips1	{ gpr_ilocks } \
@@ -466,6 +466,7 @@ if { [istarget mips*-*-vxworks*] } {
     run_dump_test_arches "branch-misc-2pic-64" [mips_arch_list_matching mips3]
     run_dump_test "branch-misc-3"
     run_dump_test "branch-swap"
+    run_dump_test_arches "branch-self"	[mips_arch_list_all]
     run_dump_test "div"
 
     if { !$addr32 } {
Index: binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/mips16@branch-self.d
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/gas/testsuite/gas/mips/mips16@branch-self.d	2010-10-29 09:07:11.000000000 +0100
@@ -0,0 +1,24 @@
+#objdump: -dr --prefix-addresses --show-raw-insn
+#name: MIPS branches to self
+#as: -32
+#source: branch-self.s
+
+# Test various ways to request a branch to self (MIPS16).
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+([0-9a-f]+) <[^>]*> db40      	sw	v0,0\(v1\)
+([0-9a-f]+) <[^>]*> 17ff      	b	\1 <.*>
+([0-9a-f]+) <[^>]*> db40      	sw	v0,0\(v1\)
+([0-9a-f]+) <[^>]*> 17ff      	b	\1 <.*>
+([0-9a-f]+) <[^>]*> db40      	sw	v0,0\(v1\)
+([0-9a-f]+) <[^>]*> 17ff      	b	\1 <.*>
+([0-9a-f]+) <[^>]*> db40      	sw	v0,0\(v1\)
+([0-9a-f]+) <[^>]*> 17ff      	b	\1 <.*>
+([0-9a-f]+) <[^>]*> db40      	sw	v0,0\(v1\)
+([0-9a-f]+) <[^>]*> 17ff      	b	\1 <.*>
+([0-9a-f]+) <[^>]*> db40      	sw	v0,0\(v1\)
+([0-9a-f]+) <[^>]*> 17ff      	b	\1 <.*>
+	\.\.\.
+	\.\.\.

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• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

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