[PATCH 2/8] Make aarch64_decode_adrp handle both ADR and ADRP instructions

[Yao Qi <qiyaoltc@gmail.com>]

From: Pierre Langlois <pierre.langlois@arm.com>

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.
---
 gdb/aarch64-tdep.c      |  4 +++-
 gdb/arch/aarch64-insn.c | 29 ++++++++++++++++++++++++-----
 gdb/arch/aarch64-insn.h |  3 ++-
 3 files changed, 29 insertions(+), 7 deletions(-)

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);
-- 
1.9.1