MIPS/GAS: Correct branch relaxation for weak symbols

Weak symbols can be preempted at link time so always choose the longer
sequence in branch relaxation, according to the relaxation level chosen,
so that any symbol finally used as the branch target is reachable.

2016-04-13  Maciej W. Rozycki  <macro@imgtec.com>
            Andrew Bennett  <andrew.bennett@imgtec.com>

	gas/
	* config/tc-mips.c (relaxed_branch_length): Use the long
	sequence where the target is a weak symbol.
	(relaxed_micromips_32bit_branch_length): Likewise.
	(relaxed_micromips_16bit_branch_length): Likewise.
	* testsuite/gas/mips/branch-weak-1.d: New test.
	* testsuite/gas/mips/branch-weak-2.d: New test.
	* testsuite/gas/mips/branch-weak-3.d: New test.
	* testsuite/gas/mips/branch-weak-4.d: New test.
	* testsuite/gas/mips/branch-weak-5.d: New test.
	* testsuite/gas/mips/branch-weak.l: New stderr output.
	* testsuite/gas/mips/branch-weak.s: New test source.
	* testsuite/gas/mips/mips.exp: Run the new tests.

10 files changed, 122 insertions, 0 deletions

diff --git a/gas/ChangeLog b/gas/ChangeLog
index b5548b3..46605f9 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,4 +1,20 @@
 2016-04-13  Maciej W. Rozycki  <macro@imgtec.com>
+	    Andrew Bennett  <andrew.bennett@imgtec.com>
+
+	* config/tc-mips.c (relaxed_branch_length): Use the long
+	sequence where the target is a weak symbol.
+	(relaxed_micromips_32bit_branch_length): Likewise.
+	(relaxed_micromips_16bit_branch_length): Likewise.
+	* testsuite/gas/mips/branch-weak-1.d: New test.
+	* testsuite/gas/mips/branch-weak-2.d: New test.
+	* testsuite/gas/mips/branch-weak-3.d: New test.
+	* testsuite/gas/mips/branch-weak-4.d: New test.
+	* testsuite/gas/mips/branch-weak-5.d: New test.
+	* testsuite/gas/mips/branch-weak.l: New stderr output.
+	* testsuite/gas/mips/branch-weak.s: New test source.
+	* testsuite/gas/mips/mips.exp: Run the new tests.
+
+2016-04-13  Maciej W. Rozycki  <macro@imgtec.com>
 
 	* config/tc-mips.c (relaxed_branch_length): Use the long
 	sequence where the distance cannot be determined.
diff --git a/gas/config/tc-mips.c b/gas/config/tc-mips.c
index dba147a..118b91d 100644
--- a/gas/config/tc-mips.c
+++ b/gas/config/tc-mips.c
@@ -16798,6 +16798,7 @@ relaxed_branch_length (fragS *fragp, asection *sec, int update)
 
   if (fragp
       && S_IS_DEFINED (fragp->fr_symbol)
+      && !S_IS_WEAK (fragp->fr_symbol)
       && sec == S_GET_SEGMENT (fragp->fr_symbol))
     {
       addressT addr;
@@ -16861,6 +16862,7 @@ relaxed_micromips_32bit_branch_length (fragS *fragp, asection *sec, int update)
 
   if (fragp
       && S_IS_DEFINED (fragp->fr_symbol)
+      && !S_IS_WEAK (fragp->fr_symbol)
       && sec == S_GET_SEGMENT (fragp->fr_symbol))
     {
       addressT addr;
@@ -16952,6 +16954,7 @@ relaxed_micromips_16bit_branch_length (fragS *fragp, asection *sec, int update)
 
   if (fragp
       && S_IS_DEFINED (fragp->fr_symbol)
+      && !S_IS_WEAK (fragp->fr_symbol)
       && sec == S_GET_SEGMENT (fragp->fr_symbol))
     {
       addressT addr;
diff --git a/gas/testsuite/gas/mips/branch-weak-1.d b/gas/testsuite/gas/mips/branch-weak-1.d
new file mode 100644
index 0000000..859a2ca
--- /dev/null
+++ b/gas/testsuite/gas/mips/branch-weak-1.d
@@ -0,0 +1,15 @@
+#objdump: -dr --prefix-addresses --show-raw-insn
+#name: MIPS branch to a weak symbol
+#as: -32 --defsym align=12
+#source: branch-weak.s
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> 1000ffff 	b	00000000 <foo>
+[ 	]*[0-9a-f]+: R_MIPS_PC16	bar
+[0-9a-f]+ <[^>]*> 00000000 	nop
+	\.\.\.
+[0-9a-f]+ <[^>]*> 03e00008 	jr	ra
+[0-9a-f]+ <[^>]*> 00000000 	nop
+	\.\.\.
diff --git a/gas/testsuite/gas/mips/branch-weak-2.d b/gas/testsuite/gas/mips/branch-weak-2.d
new file mode 100644
index 0000000..d97bace
--- /dev/null
+++ b/gas/testsuite/gas/mips/branch-weak-2.d
@@ -0,0 +1,15 @@
+#objdump: -dr --prefix-addresses --show-raw-insn
+#name: microMIPS branch to a weak symbol
+#as: -32 -mmicromips --defsym align=12
+#source: branch-weak.s
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> 9400 fffe 	b	00000000 <foo>
+[ 	]*[0-9a-f]+: R_MICROMIPS_PC16_S1	bar
+[0-9a-f]+ <[^>]*> 0c00      	nop
+	\.\.\.
+[0-9a-f]+ <[^>]*> 459f      	jr	ra
+[0-9a-f]+ <[^>]*> 0c00      	nop
+	\.\.\.
diff --git a/gas/testsuite/gas/mips/branch-weak-3.d b/gas/testsuite/gas/mips/branch-weak-3.d
new file mode 100644
index 0000000..93e06f5
--- /dev/null
+++ b/gas/testsuite/gas/mips/branch-weak-3.d
@@ -0,0 +1,16 @@
+#objdump: -dr --prefix-addresses --show-raw-insn
+#name: MIPS relaxed branch to a weak symbol
+#as: -32 --relax-branch --defsym align=12
+#source: branch-weak.s
+#stderr: branch-weak.l
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> 08000000 	j	00000000 <foo>
+[ 	]*[0-9a-f]+: R_MIPS_26	bar
+[0-9a-f]+ <[^>]*> 00000000 	nop
+	\.\.\.
+[0-9a-f]+ <[^>]*> 03e00008 	jr	ra
+[0-9a-f]+ <[^>]*> 00000000 	nop
+	\.\.\.
diff --git a/gas/testsuite/gas/mips/branch-weak-4.d b/gas/testsuite/gas/mips/branch-weak-4.d
new file mode 100644
index 0000000..c8a2a4b
--- /dev/null
+++ b/gas/testsuite/gas/mips/branch-weak-4.d
@@ -0,0 +1,16 @@
+#objdump: -dr --prefix-addresses --show-raw-insn
+#name: microMIPS relaxed branch to a weak symbol
+#as: -32 -mmicromips --relax-branch --defsym align=12
+#source: branch-weak.s
+#stderr: branch-weak.l
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> d400 0000 	j	00000000 <foo>
+[ 	]*[0-9a-f]+: R_MICROMIPS_26_S1	bar
+[0-9a-f]+ <[^>]*> 0c00      	nop
+	\.\.\.
+[0-9a-f]+ <[^>]*> 459f      	jr	ra
+[0-9a-f]+ <[^>]*> 0c00      	nop
+	\.\.\.
diff --git a/gas/testsuite/gas/mips/branch-weak-5.d b/gas/testsuite/gas/mips/branch-weak-5.d
new file mode 100644
index 0000000..caeee97
--- /dev/null
+++ b/gas/testsuite/gas/mips/branch-weak-5.d
@@ -0,0 +1,15 @@
+#objdump: -dr --prefix-addresses --show-raw-insn
+#name: microMIPS short branch to a weak symbol
+#as: -32 -mmicromips --defsym align=4
+#source: branch-weak.s
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> 9400 fffe 	b	00000000 <foo>
+[ 	]*[0-9a-f]+: R_MICROMIPS_PC16_S1	bar
+[0-9a-f]+ <[^>]*> 0c00      	nop
+	\.\.\.
+[0-9a-f]+ <[^>]*> 459f      	jr	ra
+[0-9a-f]+ <[^>]*> 0c00      	nop
+	\.\.\.
diff --git a/gas/testsuite/gas/mips/branch-weak.l b/gas/testsuite/gas/mips/branch-weak.l
new file mode 100644
index 0000000..b0c248a
--- /dev/null
+++ b/gas/testsuite/gas/mips/branch-weak.l
@@ -0,0 +1,2 @@
+.*: Assembler messages:
+.*:6: Warning: relaxed out-of-range branch into a jump
diff --git a/gas/testsuite/gas/mips/branch-weak.s b/gas/testsuite/gas/mips/branch-weak.s
new file mode 100644
index 0000000..eedef7a
--- /dev/null
+++ b/gas/testsuite/gas/mips/branch-weak.s
@@ -0,0 +1,19 @@
+	.text
+	.align	4, 0
+	.globl	foo
+	.ent	foo
+foo:
+	b	bar
+	.end	foo
+
+	.align	align, 0
+	.globl	bar
+	.weak	bar
+	.ent	bar
+bar:
+	jr	$ra
+	.end	bar
+
+# Force some (non-delay-slot) zero bytes, to make 'objdump' print ...
+	.align  4, 0
+	.space  16
diff --git a/gas/testsuite/gas/mips/mips.exp b/gas/testsuite/gas/mips/mips.exp
index ad3cdfe..078fde2 100644
--- a/gas/testsuite/gas/mips/mips.exp
+++ b/gas/testsuite/gas/mips/mips.exp
@@ -583,6 +583,11 @@ if { [istarget mips*-*-vxworks*] } {
     run_dump_test "branch-extern-2"
     run_dump_test "branch-extern-3"
     run_dump_test "branch-extern-4"
+    run_dump_test "branch-weak-1"
+    run_dump_test "branch-weak-2"
+    run_dump_test "branch-weak-3"
+    run_dump_test "branch-weak-4"
+    run_dump_test "branch-weak-5"
 
     run_dump_test "compact-eh-eb-1"
     run_dump_test "compact-eh-eb-2"