Make aarch64_decode_adrp handle both ADR and ADRP instructions

We will need to decode both ADR and ADRP instructions in GDBserver.
This patch makes common code handle both cases, even if GDB only needs
to decode the ADRP instruction.

gdb/ChangeLog:

	* aarch64-tdep.c (aarch64_analyze_prologue): New is_adrp
	variable.  Call aarch64_decode_adr instead of
	aarch64_decode_adrp.
	* arch/aarch64-insn.h (aarch64_decode_adrp): Delete.
	(aarch64_decode_adr): New function declaration.
	* arch/aarch64-insn.c (aarch64_decode_adrp): Delete.
	(aarch64_decode_adr): New function, factored out from
	aarch64_decode_adrp to decode both adr and adrp instructions.

4 files changed, 40 insertions, 7 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 7d8feeb..935daf1 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,16 @@
 2015-09-21  Pierre Langlois  <pierre.langlois@arm.com>
 
+	* aarch64-tdep.c (aarch64_analyze_prologue): New is_adrp
+	variable.  Call aarch64_decode_adr instead of
+	aarch64_decode_adrp.
+	* arch/aarch64-insn.h (aarch64_decode_adrp): Delete.
+	(aarch64_decode_adr): New function declaration.
+	* arch/aarch64-insn.c (aarch64_decode_adrp): Delete.
+	(aarch64_decode_adr): New function, factored out from
+	aarch64_decode_adrp to decode both adr and adrp instructions.
+
+2015-09-21  Pierre Langlois  <pierre.langlois@arm.com>
+
 	* Makefile.in (ALL_64_TARGET_OBS): Add aarch64-insn.o.
 	(HFILES_NO_SRCDIR): Add arch/aarch64-insn.h.
 	(aarch64-insn.o): New rule.
diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 92e2404..da61e54 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -551,13 +551,15 @@ aarch64_analyze_prologue (struct gdbarch *gdbarch,
       int is_cbnz;
       int is_tbnz;
       unsigned bit;
+      int is_adrp;
       int32_t offset;
 
       insn = read_memory_unsigned_integer (start, 4, byte_order_for_code);
 
       if (aarch64_decode_add_sub_imm (start, insn, &rd, &rn, &imm))
 	regs[rd] = pv_add_constant (regs[rn], imm);
-      else if (aarch64_decode_adrp (start, insn, &rd))
+      else if (aarch64_decode_adr (start, insn, &is_adrp, &rd, &offset)
+	       && is_adrp)
 	regs[rd] = pv_unknown ();
       else if (aarch64_decode_b (start, insn, &is_link, &offset))
 	{
diff --git a/gdb/arch/aarch64-insn.c b/gdb/arch/aarch64-insn.c
index 3a289a2..13d0013 100644
--- a/gdb/arch/aarch64-insn.c
+++ b/gdb/arch/aarch64-insn.c
@@ -55,25 +55,44 @@ decode_masked_match (uint32_t insn, uint32_t mask, uint32_t pattern)
   return (insn & mask) == pattern;
 }
 
-/* Decode an opcode if it represents an ADRP instruction.
+/* Decode an opcode if it represents an ADR or ADRP instruction.
 
    ADDR specifies the address of the opcode.
    INSN specifies the opcode to test.
+   IS_ADRP receives the 'op' field from the decoded instruction.
    RD receives the 'rd' field from the decoded instruction.
+   OFFSET receives the 'immhi:immlo' field from the decoded instruction.
 
    Return 1 if the opcodes matches and is decoded, otherwise 0.  */
 
 int
-aarch64_decode_adrp (CORE_ADDR addr, uint32_t insn, unsigned *rd)
+aarch64_decode_adr (CORE_ADDR addr, uint32_t insn, int *is_adrp,
+		    unsigned *rd, int32_t *offset)
 {
-  if (decode_masked_match (insn, 0x9f000000, 0x90000000))
+  /* adr  0ii1 0000 iiii iiii iiii iiii iiir rrrr */
+  /* adrp 1ii1 0000 iiii iiii iiii iiii iiir rrrr */
+  if (decode_masked_match (insn, 0x1f000000, 0x10000000))
     {
+      uint32_t immlo = (insn >> 29) & 0x3;
+      int32_t immhi = extract_signed_bitfield (insn, 19, 5) << 2;
+
+      *is_adrp = (insn >> 31) & 0x1;
       *rd = (insn >> 0) & 0x1f;
 
+      if (*is_adrp)
+	{
+	  /* The ADRP instruction has an offset with a -/+ 4GB range,
+	     encoded as (immhi:immlo * 4096).  */
+	  *offset = (immhi | immlo) * 4096;
+	}
+      else
+	*offset = (immhi | immlo);
+
       if (aarch64_debug)
 	{
-	  debug_printf ("decode: 0x%s 0x%x adrp x%u, #?\n",
-			core_addr_to_string_nz (addr), insn, *rd);
+	  debug_printf ("decode: 0x%s 0x%x %s x%u, #?\n",
+			core_addr_to_string_nz (addr), insn,
+			*is_adrp ?  "adrp" : "adr", *rd);
 	}
       return 1;
     }
diff --git a/gdb/arch/aarch64-insn.h b/gdb/arch/aarch64-insn.h
index 7775a34..2facb44 100644
--- a/gdb/arch/aarch64-insn.h
+++ b/gdb/arch/aarch64-insn.h
@@ -21,7 +21,8 @@
 
 extern int aarch64_debug;
 
-int aarch64_decode_adrp (CORE_ADDR addr, uint32_t insn, unsigned *rd);
+int aarch64_decode_adr (CORE_ADDR addr, uint32_t insn, int *is_adrp,
+			unsigned *rd, int32_t *offset);
 
 int aarch64_decode_b (CORE_ADDR addr, uint32_t insn, int *is_bl,
 		      int32_t *offset);