Change the ARM assembler's ADR and ADRl pseudo-ops so that they will only set the bottom bit of imported thumb function symbols if the -mthumb-interwork option is active.

For more information see the email thread starting here:
https://www.sourceware.org/ml/binutils/2018-05/msg00348.html

	PR 21458
	* tc-arm.c (do_adr): Only set the bottom bit of an imported thumb
	function symbol address if -mthumb-interwork is active.
	(do_adrl): Likewise.
	* doc/c-arm.texi: Update descriptions of the -mthumb-interwork
	option and the ADR and ADRL pseudo-ops.
	* NEWS: Mention the new behaviour of the ADR and ADRL pseudo-ops.
	* testsuite/gas/arm/pr21458.d: Add -mthumb-interwork option to
	assembler command line.
	* testsuite/gas/arm/adr.d: Likewise.
	* testsuite/gas/arm/adrl.d: Likewise.

7 files changed, 44 insertions, 6 deletions

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 33ba540..d22dd1f 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,17 @@
+2018-06-20  Nick Clifton  <nickc@redhat.com>
+
+	PR 21458
+	* tc-arm.c (do_adr): Only set the bottom bit of an imported thumb
+	function symbol address if -mthumb-interwork is active.
+	(do_adrl): Likewise.
+	* doc/c-arm.texi: Update descriptions of the -mthumb-interwork
+	option and the ADR and ADRL pseudo-ops.
+	* NEWS: Mention the new behaviour of the ADR and ADRL pseudo-ops.
+	* testsuite/gas/arm/pr21458.d: Add -mthumb-interwork option to
+	assembler command line.
+	* testsuite/gas/arm/adr.d: Likewise.
+	* testsuite/gas/arm/adrl.d: Likewise.
+
 2018-06-20  Sebastian Huber  <sebastian.huber@embedded-brains.de>
 
 	PR gas/23305
diff --git a/gas/NEWS b/gas/NEWS
index 9dfc845..474ff42 100644
--- a/gas/NEWS
+++ b/gas/NEWS
@@ -1,5 +1,9 @@
 -*- text -*-
 
+* The ADR and ADRL pseudo-instructions supported by the ARM assembler
+  now only set the bottom bit of the address of thumb function symbols
+  if the -mthumb-interwork command line option is active.
+
 * Add support for the MIPS Global INValidate (GINV) ASE.
 
 * Add support for the MIPS Cyclic Redudancy Check (CRC) ASE.
diff --git a/gas/config/tc-arm.c b/gas/config/tc-arm.c
index 2529d2a..6a9a655 100644
--- a/gas/config/tc-arm.c
+++ b/gas/config/tc-arm.c
@@ -8419,11 +8419,12 @@ do_adr (void)
   inst.reloc.pc_rel = 1;
   inst.reloc.exp.X_add_number -= 8;
 
-  if (inst.reloc.exp.X_op == O_symbol
+  if (support_interwork
+      && inst.reloc.exp.X_op == O_symbol
       && inst.reloc.exp.X_add_symbol != NULL
       && S_IS_DEFINED (inst.reloc.exp.X_add_symbol)
       && THUMB_IS_FUNC (inst.reloc.exp.X_add_symbol))
-    inst.reloc.exp.X_add_number += 1;
+    inst.reloc.exp.X_add_number |= 1;
 }
 
 /* This is a pseudo-op of the form "adrl rd, label" to be converted
@@ -8443,11 +8444,12 @@ do_adrl (void)
   inst.size		       = INSN_SIZE * 2;
   inst.reloc.exp.X_add_number -= 8;
 
-  if (inst.reloc.exp.X_op == O_symbol
+  if (support_interwork
+      && inst.reloc.exp.X_op == O_symbol
       && inst.reloc.exp.X_add_symbol != NULL
       && S_IS_DEFINED (inst.reloc.exp.X_add_symbol)
       && THUMB_IS_FUNC (inst.reloc.exp.X_add_symbol))
-    inst.reloc.exp.X_add_number += 1;
+    inst.reloc.exp.X_add_number |= 1;
 }
 
 static void
diff --git a/gas/doc/c-arm.texi b/gas/doc/c-arm.texi
index cd533ca..4683b8a 100644
--- a/gas/doc/c-arm.texi
+++ b/gas/doc/c-arm.texi
@@ -318,7 +318,8 @@ instructions; that is, it should behave as though the file starts with a
 @cindex @code{-mthumb-interwork} command line option, ARM
 @item -mthumb-interwork
 This option specifies that the output generated by the assembler should
-be marked as supporting interworking.
+be marked as supporting interworking.  It also affects the behaviour
+of the @code{ADR} and @code{ADRL} pseudo opcodes.
 
 @cindex @code{-mimplicit-it} command line option, ARM
 @item -mimplicit-it=never
@@ -1061,6 +1062,16 @@ out of range, or if it is not defined in the same file (and section) as
 the ADR instruction, then an error will be generated.  This instruction
 will not make use of the literal pool.
 
+If @var{label} is a thumb function symbol, and thumb interworking has
+been enabled via the @option{-mthumb-interwork} option then the bottom
+bit of the value stored into @var{register} will be set.  This allows
+the following sequence to work as expected:
+
+@smallexample
+  adr     r0, thumb_function
+  blx     r0
+@end smallexample
+
 @cindex @code{ADRL reg,<label>} pseudo op, ARM
 @item ADRL
 @smallexample
@@ -1077,6 +1088,10 @@ If the label is out of range, or if it is not defined in the same file
 (and section) as the ADRL instruction, then an error will be generated.
 This instruction will not make use of the literal pool.
 
+If @var{label} is a thumb function symbol, and thumb interworking has
+been enabled via the @option{-mthumb-interwork} option then the bottom
+bit of the value stored into @var{register} will be set.
+
 @end table
 
 For information on the ARM or Thumb instruction sets, see @cite{ARM
diff --git a/gas/testsuite/gas/arm/adr.d b/gas/testsuite/gas/arm/adr.d
index ee74154..13722cd 100644
--- a/gas/testsuite/gas/arm/adr.d
+++ b/gas/testsuite/gas/arm/adr.d
@@ -1,3 +1,4 @@
+#as: -mthumb-interwork
 #objdump: -dr --prefix-addresses --show-raw-insn
 #name: ADR
 
diff --git a/gas/testsuite/gas/arm/adrl.d b/gas/testsuite/gas/arm/adrl.d
index 6276e8d..b6011f1 100644
--- a/gas/testsuite/gas/arm/adrl.d
+++ b/gas/testsuite/gas/arm/adrl.d
@@ -1,3 +1,4 @@
+#as: -mthumb-interwork
 #objdump: -dr --prefix-addresses --show-raw-insn
 #name: ADRL
 
diff --git a/gas/testsuite/gas/arm/pr21458.d b/gas/testsuite/gas/arm/pr21458.d
index 5410e7a..b567d84 100644
--- a/gas/testsuite/gas/arm/pr21458.d
+++ b/gas/testsuite/gas/arm/pr21458.d
@@ -1,8 +1,9 @@
+#as: -mthumb-interwork
 #objdump: -d --prefix-addresses --show-raw-insn
 #name: ADR(L) for Thumb functions
 #skip: *-*-pe *-wince-* *-*-vxworks
 
-# Test that using ADR(L) on thumb function symbols sets the T bit.
+# Test that using ADR(L) on thumb function symbols sets the T bit when -mthumb-interwork is active.
 
 .*: +file format .*arm.*