[ARM] Fix expansion of ldr pseudo instructionusers/ARM/embedded-binutils-2_28-branch-2017q2

The LDR rX, =cst pseudo-instruction suffers from two issues for loading
integer constants in Thumb mode:

- movs is used if the constant and register can be encoded using that
  instruction which leads to unexpected behavior due to its flag-setting
  behavior
- mov.w, movw and mvn are used for r13 (sp) and r15 (pc) but these
  encoding are marked as UNPREDICTABLE

This patch fixes those issues and update testing accordingly.

2017-06-20  Thomas Preud'homme  <thomas.preudhomme@arm.com>

	Backport from mainline
	2017-04-24  Thomas Preud'homme  <thomas.preudhomme@arm.com>

gas/
	* config/tc-arm.c (move_or_literal_pool): Remove code generating MOVS.
	Forbid MOV.W and MOVW if destination is SP or PC.
	* testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.s: Explain
	expectation of LDR not generating a MOVS for low registers and small
	constants.  Add tests of MOVW generation.
	* testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.d: Update
	expected disassembly.

4 files changed, 43 insertions, 24 deletions

diff --git a/gas/ChangeLog b/gas/ChangeLog
index e752375..93f7c63 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,6 +1,19 @@
 2017-06-20  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
 	Backport from mainline
+	2017-04-24  Thomas Preud'homme  <thomas.preudhomme@arm.com>
+
+	* config/tc-arm.c (move_or_literal_pool): Remove code generating MOVS.
+	Forbid MOV.W and MOVW if destination is SP or PC.
+	* testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.s: Explain
+	expectation of LDR not generating a MOVS for low registers and small
+	constants.  Add tests of MOVW generation.
+	* testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.d: Update
+	expected disassembly.
+
+2017-06-20  Thomas Preud'homme  <thomas.preudhomme@arm.com>
+
+	Backport from mainline
 	2017-05-08  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
 	* testsuite/ld-arm/arm-elf.exp
diff --git a/gas/config/tc-arm.c b/gas/config/tc-arm.c
index 60bda51..0820b96 100644
--- a/gas/config/tc-arm.c
+++ b/gas/config/tc-arm.c
@@ -7955,17 +7955,13 @@ move_or_literal_pool (int i, enum lit_type t, bfd_boolean mode_3)
 	{
 	  if (thumb_p)
 	    {
-	      /* This can be encoded only for a low register.  */
-	      if ((v & ~0xFF) == 0 && (inst.operands[i].reg < 8))
-		{
-		  /* This can be done with a mov(1) instruction.  */
-		  inst.instruction = T_OPCODE_MOV_I8 | (inst.operands[i].reg << 8);
-		  inst.instruction |= v;
-		  return TRUE;
-		}
+	      /* LDR should not use lead in a flag-setting instruction being
+		 chosen so we do not check whether movs can be used.  */
 
-	      if (ARM_CPU_HAS_FEATURE (cpu_variant, arm_ext_v6t2)
+	      if ((ARM_CPU_HAS_FEATURE (cpu_variant, arm_ext_v6t2)
 		  || ARM_CPU_HAS_FEATURE (cpu_variant, arm_ext_v6t2_v8m))
+		  && inst.operands[i].reg != 13
+		  && inst.operands[i].reg != 15)
 		{
 		  /* Check if on thumb2 it can be done with a mov.w, mvn or
 		     movw instruction.  */
diff --git a/gas/testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.d b/gas/testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.d
index 55b5f17..7afc135 100644
--- a/gas/testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.d
+++ b/gas/testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.d
@@ -6,19 +6,23 @@
 .*: +file format .*arm.*
 
 Disassembly of section \.text:
-0[0-9a-f]+ <[^>]+> 2000[[:space:]]+movs[[:space:]]+r0, #0.*
-0[0-9a-f]+ <[^>]+> 2108[[:space:]]+movs[[:space:]]+r1, #8.*
-0[0-9a-f]+ <[^>]+> 2251[[:space:]]+movs[[:space:]]+r2, #81.*
-0[0-9a-f]+ <[^>]+> 231f[[:space:]]+movs[[:space:]]+r3, #31.*
-0[0-9a-f]+ <[^>]+> 242f[[:space:]]+movs[[:space:]]+r4, #47.*
-0[0-9a-f]+ <[^>]+> 253f[[:space:]]+movs[[:space:]]+r5, #63.*
-0[0-9a-f]+ <[^>]+> 2680[[:space:]]+movs[[:space:]]+r6, #128.*
-0[0-9a-f]+ <[^>]+> 27ff[[:space:]]+movs[[:space:]]+r7, #255.*
+0[0-9a-f]+ <[^>]+> f04f 0000[[:space:]]+mov\.w[[:space:]]+r0, #0.*
+0[0-9a-f]+ <[^>]+> f04f 0108[[:space:]]+mov\.w[[:space:]]+r1, #8.*
+0[0-9a-f]+ <[^>]+> f04f 0251[[:space:]]+mov\.w[[:space:]]+r2, #81.*
+0[0-9a-f]+ <[^>]+> f04f 031f[[:space:]]+mov\.w[[:space:]]+r3, #31.*
+0[0-9a-f]+ <[^>]+> f04f 042f[[:space:]]+mov\.w[[:space:]]+r4, #47.*
+0[0-9a-f]+ <[^>]+> f04f 053f[[:space:]]+mov\.w[[:space:]]+r5, #63.*
+0[0-9a-f]+ <[^>]+> f04f 0680[[:space:]]+mov\.w[[:space:]]+r6, #128.*
+0[0-9a-f]+ <[^>]+> f04f 07ff[[:space:]]+mov\.w[[:space:]]+r7, #255.*
 0[0-9a-f]+ <[^>]+> f04f 0800[[:space:]]+mov\.w[[:space:]]+r8, #0.*
 0[0-9a-f]+ <[^>]+> f04f 0908[[:space:]]+mov\.w[[:space:]]+r9, #8.*
 0[0-9a-f]+ <[^>]+> f04f 0a51[[:space:]]+mov\.w[[:space:]]+sl, #81.*
 0[0-9a-f]+ <[^>]+> f04f 0b1f[[:space:]]+mov\.w[[:space:]]+fp, #31.*
 0[0-9a-f]+ <[^>]+> f04f 0c2f[[:space:]]+mov\.w[[:space:]]+ip, #47.*
-0[0-9a-f]+ <[^>]+> f04f 0d3f[[:space:]]+mov\.w[[:space:]]+sp, #63.*
 0[0-9a-f]+ <[^>]+> f04f 0e80[[:space:]]+mov\.w[[:space:]]+lr, #128.*
-0[0-9a-f]+ <[^>]+> f04f 0fff[[:space:]]+mov\.w[[:space:]]+pc, #255.*
+0[0-9a-f]+ <[^>]+> f64f 78ff[[:space:]]+movw[[:space:]]+r8, #65535.*
+0[0-9a-f]+ <[^>]+> f24f 09f0[[:space:]]+movw[[:space:]]+r9, #61680.*
+0[0-9a-f]+ <[^>]+> f8df d004[[:space:]]+ldr\.w[[:space:]]+sp, \[pc, #4\].*
+0[0-9a-f]+ <[^>]+> f8df f004[[:space:]]+ldr\.w[[:space:]]+pc, \[pc, #4\].*
+0[0-9a-f]+ <[^>]+> 0000003f[[:space:]]+.word[[:space:]]+0x0000003f.*
+0[0-9a-f]+ <[^>]+> 000000ff[[:space:]]+.word[[:space:]]+0x000000ff.*
diff --git a/gas/testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.s b/gas/testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.s
index d225410..b473857 100644
--- a/gas/testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.s
+++ b/gas/testsuite/gas/arm/thumb2_ldr_immediate_highregs_armv6t2.s
@@ -2,8 +2,8 @@
 	.syntax unified
 	.thumb_func
 thumb2_ldr:
-	# These can be encoded into movs since constant is small
-	# And register can be encoded in 3 bits
+	# These must be encoded into mov.w despite constant and register being
+	# small enough as ldr should not generate a flag-setting instruction.
 	ldr r0,=0x00
 	ldr r1,=0x08
 	ldr r2,=0x51
@@ -12,13 +12,19 @@ thumb2_ldr:
 	ldr r5,=0x3F
 	ldr r6,=0x80
 	ldr r7,=0xFF
-	# These shall be encoded into mov.w
-	# Since register cannot be encoded in 3 bits
+	# These shall be encoded into mov.w since register cannot be encoded in
+	# 3 bits
 	ldr r8,=0x00
 	ldr r9,=0x08
 	ldr r10,=0x51
 	ldr r11,=0x1F
 	ldr r12,=0x2F
-	ldr r13,=0x3F
 	ldr r14,=0x80
+	# These shall be encoded into movw since immediate cannot be encoded
+	# with mov.w
+	ldr r8,=0xFFFF
+	ldr r9,=0xF0F0
+	# These should be encoded as ldr since mov immediate is unpredictable
+	# for sp and pc
+	ldr r13,=0x3F
 	ldr r15,=0xFF