MIPS/BFD: Discard ineligible JALR relocations right away

Discard R_MIPS_JALR and R_MICROMIPS_JALR relocations associated with
jumps that cannot be converted to an equivalent branch right away in
`mips_elf_calculate_relocation' rather than letting them through to
`mips_elf_perform_relocation'.  This includes cross-mode jumps which
need to flip the ISA bit or jumps to a misaligned location that cannot
be encoded with a branch, in addition to preemptible symbol references
already handled.

Cross-mode jumps are actually already rejected as the conversion is made
in `mips_elf_perform_relocation', so in this case this change only saves
some processing.  Jumps to a misaligned location are however converted,
with bits causing misalignment lost, making resulting code functionally
different even if the lone effect is avoiding an address error exception
with an instruction fetch at the jump destination requested.

Add test cases suitable, also including GAS verification to confirm that
the JALR relocations explicitly requested have indeed been output in the
intermediate objects used.

	bfd/
	* elfxx-mips.c (mips_elf_calculate_relocation) <R_MIPS_JALR>
	<R_MICROMIPS_JALR>: Discard relocation if `cross_mode_jump_p'
	or misaligned.

	gas/
	* testsuite/gas/mips/jalr4.d: New test.
	* testsuite/gas/mips/jalr4-n32.d: New test.
	* testsuite/gas/mips/jalr4-n64.d: New test.
	* testsuite/gas/mips/jalr4.s: New test source.
	* testsuite/gas/mips/mips.exp: Run the new tests.

	ld/
	* testsuite/ld-mips-elf/jalr4.dd: New test.
	* testsuite/ld-mips-elf/mips-elf.exp: Run the new test.

6 files changed, 156 insertions, 0 deletions

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 415237c..0f46787 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,11 @@
+2017-02-23  Maciej W. Rozycki  <macro@imgtec.com>
+
+	* testsuite/gas/mips/jalr4.d: New test.
+	* testsuite/gas/mips/jalr4-n32.d: New test.
+	* testsuite/gas/mips/jalr4-n64.d: New test.
+	* testsuite/gas/mips/jalr4.s: New test source.
+	* testsuite/gas/mips/mips.exp: Run the new tests.
+
 2017-02-23  Sheldon Lobo <sheldon.lobo@oracle.com>
 
 	Add support for associating SPARC ASIs with an architecture level.
diff --git a/gas/testsuite/gas/mips/jalr4-n32.d b/gas/testsuite/gas/mips/jalr4-n32.d
new file mode 100644
index 0000000..fde29f5
--- /dev/null
+++ b/gas/testsuite/gas/mips/jalr4-n32.d
@@ -0,0 +1,5 @@
+#objdump: -dr --prefix-addresses --show-raw-insn
+#name: MIPS JALR reloc unaligned/cross-mode (n32)
+#as: -n32
+#source: jalr4.s
+#dump: jalr4.d
diff --git a/gas/testsuite/gas/mips/jalr4-n64.d b/gas/testsuite/gas/mips/jalr4-n64.d
new file mode 100644
index 0000000..b61fc23
--- /dev/null
+++ b/gas/testsuite/gas/mips/jalr4-n64.d
@@ -0,0 +1,42 @@
+#objdump: -dr --prefix-addresses --show-raw-insn
+#name: MIPS JALR reloc unaligned/cross-mode (n64)
+#as: -64
+#source: jalr4.s
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> 0320f809 	jalr	t9
+[ 	]*[0-9a-f]+: R_MIPS_JALR	bar0
+[ 	]*[0-9a-f]+: R_MIPS_NONE	\*ABS\*
+[ 	]*[0-9a-f]+: R_MIPS_NONE	\*ABS\*
+[0-9a-f]+ <[^>]*> 00000000 	nop
+[0-9a-f]+ <[^>]*> 0320000[89] 	jr	t9
+[ 	]*[0-9a-f]+: R_MIPS_JALR	bar0
+[ 	]*[0-9a-f]+: R_MIPS_NONE	\*ABS\*
+[ 	]*[0-9a-f]+: R_MIPS_NONE	\*ABS\*
+[0-9a-f]+ <[^>]*> 00000000 	nop
+[0-9a-f]+ <[^>]*> 0320f809 	jalr	t9
+[ 	]*[0-9a-f]+: R_MIPS_JALR	bar1
+[ 	]*[0-9a-f]+: R_MIPS_NONE	\*ABS\*
+[ 	]*[0-9a-f]+: R_MIPS_NONE	\*ABS\*
+[0-9a-f]+ <[^>]*> 00000000 	nop
+[0-9a-f]+ <[^>]*> 0320000[89] 	jr	t9
+[ 	]*[0-9a-f]+: R_MIPS_JALR	bar1
+[ 	]*[0-9a-f]+: R_MIPS_NONE	\*ABS\*
+[ 	]*[0-9a-f]+: R_MIPS_NONE	\*ABS\*
+[0-9a-f]+ <[^>]*> 00000000 	nop
+[0-9a-f]+ <[^>]*> 0320f809 	jalr	t9
+[ 	]*[0-9a-f]+: R_MIPS_JALR	bar2
+[ 	]*[0-9a-f]+: R_MIPS_NONE	\*ABS\*
+[ 	]*[0-9a-f]+: R_MIPS_NONE	\*ABS\*
+[0-9a-f]+ <[^>]*> 00000000 	nop
+[0-9a-f]+ <[^>]*> 0320000[89] 	jr	t9
+[ 	]*[0-9a-f]+: R_MIPS_JALR	bar2
+[ 	]*[0-9a-f]+: R_MIPS_NONE	\*ABS\*
+[ 	]*[0-9a-f]+: R_MIPS_NONE	\*ABS\*
+[0-9a-f]+ <[^>]*> 00000000 	nop
+	\.\.\.
+	\.\.\.
+	\.\.\.
+	\.\.\.
diff --git a/gas/testsuite/gas/mips/jalr4.d b/gas/testsuite/gas/mips/jalr4.d
new file mode 100644
index 0000000..1a1afdd
--- /dev/null
+++ b/gas/testsuite/gas/mips/jalr4.d
@@ -0,0 +1,30 @@
+#objdump: -dr --prefix-addresses --show-raw-insn
+#name: MIPS JALR reloc unaligned/cross-mode (o32)
+#as: -32
+#source: jalr4.s
+
+.*: +file format .*mips.*
+
+Disassembly of section \.text:
+[0-9a-f]+ <[^>]*> 0320f809 	jalr	t9
+[ 	]*[0-9a-f]+: R_MIPS_JALR	bar0
+[0-9a-f]+ <[^>]*> 00000000 	nop
+[0-9a-f]+ <[^>]*> 0320000[89] 	jr	t9
+[ 	]*[0-9a-f]+: R_MIPS_JALR	bar0
+[0-9a-f]+ <[^>]*> 00000000 	nop
+[0-9a-f]+ <[^>]*> 0320f809 	jalr	t9
+[ 	]*[0-9a-f]+: R_MIPS_JALR	bar1
+[0-9a-f]+ <[^>]*> 00000000 	nop
+[0-9a-f]+ <[^>]*> 0320000[89] 	jr	t9
+[ 	]*[0-9a-f]+: R_MIPS_JALR	bar1
+[0-9a-f]+ <[^>]*> 00000000 	nop
+[0-9a-f]+ <[^>]*> 0320f809 	jalr	t9
+[ 	]*[0-9a-f]+: R_MIPS_JALR	bar2
+[0-9a-f]+ <[^>]*> 00000000 	nop
+[0-9a-f]+ <[^>]*> 0320000[89] 	jr	t9
+[ 	]*[0-9a-f]+: R_MIPS_JALR	bar2
+[0-9a-f]+ <[^>]*> 00000000 	nop
+	\.\.\.
+	\.\.\.
+	\.\.\.
+	\.\.\.
diff --git a/gas/testsuite/gas/mips/jalr4.s b/gas/testsuite/gas/mips/jalr4.s
new file mode 100644
index 0000000..4ad6f26
--- /dev/null
+++ b/gas/testsuite/gas/mips/jalr4.s
@@ -0,0 +1,63 @@
+	.abicalls
+	.text
+
+	.align	2
+	.globl	foo
+	.ent	foo
+foo:
+	.reloc	1f, R_MIPS_JALR, bar0
+1:	jalr	$25
+	.reloc	1f, R_MIPS_JALR, bar0
+1:	jr	$25
+	.reloc	1f, R_MIPS_JALR, bar1
+1:	jalr	$25
+	.reloc	1f, R_MIPS_JALR, bar1
+1:	jr	$25
+	.reloc	1f, R_MIPS_JALR, bar2
+1:	jalr	$25
+	.reloc	1f, R_MIPS_JALR, bar2
+1:	jr	$25
+	.end	foo
+
+# Force some (non-delay-slot) zero bytes, to make 'objdump' print ...
+	.align	4, 0
+	.space	16
+
+	.align	2
+	.globl	bar0
+	.ent	bar0
+bar0:
+	.insn
+	.end	bar0
+
+# Force some (non-delay-slot) zero bytes, to make 'objdump' print ...
+	.align	4, 0
+	.space	16
+
+	.align	2
+	.globl	bar1
+	.ent	bar1
+	.space	2
+bar1:
+	.insn
+	.end	bar1
+
+# Force some (non-delay-slot) zero bytes, to make 'objdump' print ...
+	.align	4, 0
+	.space	16
+
+	.set	mips64r2
+	.set	mips16
+	.align	2
+	.globl	bar2
+	.ent	bar2
+	.byte	0
+bar2:
+	.insn
+	.end	bar2
+	.set	nomips16
+	.set	mips0
+
+# 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 bef7106..591af50 100644
--- a/gas/testsuite/gas/mips/mips.exp
+++ b/gas/testsuite/gas/mips/mips.exp
@@ -1182,13 +1182,21 @@ if { [istarget mips*-*-vxworks*] } {
     run_dump_test "jalr2"
     run_dump_test_arches "jalr3"	[mips_arch_list_matching mips1 \
 					    !micromips]
+    run_dump_test_arches "jalr4"	[mips_arch_list_matching mips1 \
+					    !micromips]
     if $has_newabi {
 	run_dump_test_arches "jalr3-n32" \
 					[mips_arch_list_matching mips3 \
 					    !micromips]
+	run_dump_test_arches "jalr4-n32" \
+					[mips_arch_list_matching mips3 \
+					    !micromips]
 	run_dump_test_arches "jalr3-n64" \
 					[mips_arch_list_matching mips3 \
 					    !micromips]
+	run_dump_test_arches "jalr4-n64" \
+					[mips_arch_list_matching mips3 \
+					    !micromips]
     }
 
     run_dump_test_arches "aent"		[mips_arch_list_matching mips1]