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[external/binutils.git] / bfd / elf32-arm.c

diff --git a/bfd/elf32-arm.c b/bfd/elf32-arm.c
index f1895df..d1548d6 100644 (file)
--- a/bfd/elf32-arm.c
+++ b/bfd/elf32-arm.c
@@ -2329,6 +2329,11 @@ static const unsigned long dl_tlsdesc_lazy_trampoline [] =
   0x00000018, /* 4:   .word  _GLOBAL_OFFSET_TABLE_ - 2b - 8 */
 };
 
+/* NOTE: [Thumb nop sequence]
+   When adding code that transitions from Thumb to Arm the instruction that
+   should be used for the alignment padding should be 0xe7fd (b .-2) instead of
+   a nop for performance reasons.  */
+
 /* ARM FDPIC PLT entry.  */
 /* The last 5 words contain PLT lazy fragment code and data.  */
 static const bfd_vma elf32_arm_fdpic_plt_entry [] =
@@ -2446,8 +2451,8 @@ static const bfd_vma elf32_thumb2_plt_entry [] =
   0x0c00f240,          /* movw    ip, #0xNNNN    */
   0x0c00f2c0,          /* movt    ip, #0xNNNN    */
   0xf8dc44fc,          /* add     ip, pc         */
-  0xbf00f000           /* ldr.w   pc, [ip]       */
-                       /* nop                    */
+  0xe7fdf000           /* ldr.w   pc, [ip]       */
+                       /* b      .-2             */
 };
 
 /* The format of the first entry in the procedure linkage table
@@ -2487,7 +2492,7 @@ static const bfd_vma elf32_arm_vxworks_shared_plt_entry[] =
 static const bfd_vma elf32_arm_plt_thumb_stub [] =
 {
   0x4778,              /* bx pc */
-  0x46c0               /* nop   */
+  0xe7fd               /* b .-2 */
 };
 
 /* The entries in a PLT when using a DLL-based target with multiple
@@ -2574,6 +2579,8 @@ typedef struct
   int                 reloc_addend;
 }  insn_sequence;
 
+/* See note [Thumb nop sequence] when adding a veneer.  */
+
 /* Arm/Thumb -> Arm/Thumb long branch stub. On V5T and above, use blx
    to reach the stub if necessary.  */
 static const insn_sequence elf32_arm_stub_long_branch_any_any[] =
@@ -2624,7 +2631,7 @@ static const insn_sequence elf32_arm_stub_long_branch_thumb2_only_pure[] =
 static const insn_sequence elf32_arm_stub_long_branch_v4t_thumb_thumb[] =
 {
   THUMB16_INSN (0x4778),            /* bx   pc */
-  THUMB16_INSN (0x46c0),            /* nop */
+  THUMB16_INSN (0xe7fd),            /* b   .-2 */
   ARM_INSN (0xe59fc000),            /* ldr  ip, [pc, #0] */
   ARM_INSN (0xe12fff1c),            /* bx   ip */
   DATA_WORD (0, R_ARM_ABS32, 0),     /* dcd  R_ARM_ABS32(X) */
@@ -2635,7 +2642,7 @@ static const insn_sequence elf32_arm_stub_long_branch_v4t_thumb_thumb[] =
 static const insn_sequence elf32_arm_stub_long_branch_v4t_thumb_arm[] =
 {
   THUMB16_INSN (0x4778),            /* bx   pc */
-  THUMB16_INSN (0x46c0),            /* nop   */
+  THUMB16_INSN (0xe7fd),            /* b   .-2 */
   ARM_INSN (0xe51ff004),            /* ldr   pc, [pc, #-4] */
   DATA_WORD (0, R_ARM_ABS32, 0),     /* dcd   R_ARM_ABS32(X) */
 };
@@ -2645,7 +2652,7 @@ static const insn_sequence elf32_arm_stub_long_branch_v4t_thumb_arm[] =
 static const insn_sequence elf32_arm_stub_short_branch_v4t_thumb_arm[] =
 {
   THUMB16_INSN (0x4778),            /* bx   pc */
-  THUMB16_INSN (0x46c0),            /* nop   */
+  THUMB16_INSN (0xe7fd),            /* b   .-2 */
   ARM_REL_INSN (0xea000000, -8),     /* b    (X-8) */
 };
 
@@ -2683,7 +2690,7 @@ static const insn_sequence elf32_arm_stub_long_branch_v4t_arm_thumb_pic[] =
 static const insn_sequence elf32_arm_stub_long_branch_v4t_thumb_arm_pic[] =
 {
   THUMB16_INSN (0x4778),            /* bx   pc */
-  THUMB16_INSN (0x46c0),            /* nop  */
+  THUMB16_INSN (0xe7fd),            /* b   .-2 */
   ARM_INSN (0xe59fc000),            /* ldr  ip, [pc, #0] */
   ARM_INSN (0xe08cf00f),            /* add  pc, ip, pc */
   DATA_WORD (0, R_ARM_REL32, -4),     /* dcd  R_ARM_REL32(X) */
@@ -2707,7 +2714,7 @@ static const insn_sequence elf32_arm_stub_long_branch_thumb_only_pic[] =
 static const insn_sequence elf32_arm_stub_long_branch_v4t_thumb_thumb_pic[] =
 {
   THUMB16_INSN (0x4778),            /* bx   pc */
-  THUMB16_INSN (0x46c0),            /* nop */
+  THUMB16_INSN (0xe7fd),            /* b   .-2 */
   ARM_INSN (0xe59fc004),            /* ldr  ip, [pc, #4] */
   ARM_INSN (0xe08fc00c),            /* add   ip, pc, ip */
   ARM_INSN (0xe12fff1c),            /* bx   ip */
@@ -2728,7 +2735,7 @@ static const insn_sequence elf32_arm_stub_long_branch_any_tls_pic[] =
 static const insn_sequence elf32_arm_stub_long_branch_v4t_thumb_tls_pic[] =
 {
   THUMB16_INSN (0x4778),            /* bx   pc */
-  THUMB16_INSN (0x46c0),            /* nop */
+  THUMB16_INSN (0xe7fd),            /* b   .-2 */
   ARM_INSN (0xe59f1000),            /* ldr  r1, [pc, #0] */
   ARM_INSN (0xe081f00f),            /* add  pc, r1, pc */
   DATA_WORD (0, R_ARM_REL32, -4),    /* dcd  R_ARM_REL32(X) */