Arm64: re-work PR gas/27217 fix

The original approach has resulted in anomalies when . is involved in an
operand of one of the affected insns. We cannot leave . unresolved, or
else it'll be resolved at the end of assembly, then pointing to the
address of a section rather than at the insn of interest. Undo part of
the original change and instead check whether a relocation cannot be
omitted in md_apply_fix().

By resolving the expressions again, equates (see the adjustment of the
respective testcase) will now be evaluated, and hence relocations
against absolute addresses be emitted. This ought to be okay as long as
the equates aren't global (and hence can't be overridden). If a need
for such arises, quite likely the only way to address this would be to
invent yet another expression evaluation mode, leaving everything
_except_ . un-evaluated.

There's a further anomaly in how transitive equates are handled. In

	.set x, 0x12345678
	.eqv bar, x
foo:
	adrp	x0, x
	add	x0, x0, :lo12:x

	adrp	x0, bar
	add	x0, x0, :lo12:bar

the first two relocations are now against *ABS*:0x12345678 (as said
above), whereas the latter two relocations would be against x. (Before
the change here, the first two relocations are against x and the latter
two against bar.) But this is an issue seen elsewhere as well, and would
likely require adjustments in the target-independent parts of the
assembler instead of trying to hack around this for every target.

2 files changed, 23 insertions, 46 deletions

diff --git a/gas/config/tc-aarch64.c b/gas/config/tc-aarch64.c
index 779db31828..e12b68ed2c 100644
--- a/gas/config/tc-aarch64.c
+++ b/gas/config/tc-aarch64.c
@@ -565,25 +565,18 @@ static bool in_aarch64_get_expression = false;
 #define ALLOW_ABSENT  false
 #define REJECT_ABSENT true
 
-/* Fifth argument to aarch64_get_expression.  */
-#define NORMAL_RESOLUTION false
-
 /* Return TRUE if the string pointed by *STR is successfully parsed
    as an valid expression; *EP will be filled with the information of
    such an expression.  Otherwise return FALSE.
 
    If ALLOW_IMMEDIATE_PREFIX is true then skip a '#' at the start.
-   If REJECT_ABSENT is true then trat missing expressions as an error.
-   If DEFER_RESOLUTION is true, then do not resolve expressions against
-   constant symbols.  Necessary if the expression is part of a fixup
-   that uses a reloc that must be emitted.  */
+   If REJECT_ABSENT is true then trat missing expressions as an error.  */
 
 static bool
 aarch64_get_expression (expressionS *  ep,
 			char **        str,
 			bool           allow_immediate_prefix,
-			bool           reject_absent,
-			bool           defer_resolution)
+			bool           reject_absent)
 {
   char *save_in;
   segT seg;
@@ -603,10 +596,7 @@ aarch64_get_expression (expressionS *  ep,
   save_in = input_line_pointer;
   input_line_pointer = *str;
   in_aarch64_get_expression = true;
-  if (defer_resolution)
-    seg = deferred_expression (ep);
-  else
-    seg = expression (ep);
+  seg = expression (ep);
   in_aarch64_get_expression = false;
 
   if (ep->X_op == O_illegal || (reject_absent && ep->X_op == O_absent))
@@ -1035,8 +1025,7 @@ parse_typed_reg (char **ccp, aarch64_reg_type type, aarch64_reg_type *rtype,
 
       atype.defined |= NTA_HASINDEX;
 
-      aarch64_get_expression (&exp, &str, GE_NO_PREFIX, REJECT_ABSENT,
-			      NORMAL_RESOLUTION);
+      aarch64_get_expression (&exp, &str, GE_NO_PREFIX, REJECT_ABSENT);
 
       if (exp.X_op != O_constant)
 	{
@@ -1239,8 +1228,7 @@ parse_vector_reg_list (char **ccp, aarch64_reg_type type,
 	{
 	  expressionS exp;
 
-	  aarch64_get_expression (&exp, &str, GE_NO_PREFIX, REJECT_ABSENT,
-				  NORMAL_RESOLUTION);
+	  aarch64_get_expression (&exp, &str, GE_NO_PREFIX, REJECT_ABSENT);
 	  if (exp.X_op != O_constant)
 	    {
 	      set_first_syntax_error (_("constant expression required."));
@@ -2187,8 +2175,7 @@ parse_immediate_expression (char **str, expressionS *exp,
       return false;
     }
 
-  aarch64_get_expression (exp, str, GE_OPT_PREFIX, REJECT_ABSENT,
-			  NORMAL_RESOLUTION);
+  aarch64_get_expression (exp, str, GE_OPT_PREFIX, REJECT_ABSENT);
 
   if (exp->X_op == O_absent)
     {
@@ -2422,8 +2409,7 @@ parse_big_immediate (char **str, int64_t *imm, aarch64_reg_type reg_type)
       return false;
     }
 
-  aarch64_get_expression (&inst.reloc.exp, &ptr, GE_OPT_PREFIX, REJECT_ABSENT,
-			  NORMAL_RESOLUTION);
+  aarch64_get_expression (&inst.reloc.exp, &ptr, GE_OPT_PREFIX, REJECT_ABSENT);
 
   if (inst.reloc.exp.X_op == O_constant)
     *imm = inst.reloc.exp.X_add_number;
@@ -3320,8 +3306,7 @@ parse_shift (char **str, aarch64_opnd_info *operand, enum parse_shift_mode mode)
 	  p++;
 	  exp_has_prefix = 1;
 	}
-      (void) aarch64_get_expression (&exp, &p, GE_NO_PREFIX, ALLOW_ABSENT,
-				     NORMAL_RESOLUTION);
+      aarch64_get_expression (&exp, &p, GE_NO_PREFIX, ALLOW_ABSENT);
     }
   if (kind == AARCH64_MOD_MUL_VL)
     /* For consistency, give MUL VL the same shift amount as an implicit
@@ -3385,7 +3370,7 @@ parse_shifter_operand_imm (char **str, aarch64_opnd_info *operand,
 
   /* Accept an immediate expression.  */
   if (! aarch64_get_expression (&inst.reloc.exp, &p, GE_OPT_PREFIX,
-				REJECT_ABSENT, NORMAL_RESOLUTION))
+				REJECT_ABSENT))
     return false;
 
   /* Accept optional LSL for arithmetic immediate values.  */
@@ -3509,8 +3494,7 @@ parse_shifter_operand_reloc (char **str, aarch64_opnd_info *operand,
 
       /* Next, we parse the expression.  */
       if (! aarch64_get_expression (&inst.reloc.exp, str, GE_NO_PREFIX,
-				    REJECT_ABSENT,
-				    aarch64_force_reloc (entry->add_type) == 1))
+				    REJECT_ABSENT))
 	return false;
       
       /* Record the relocation type (use the ADD variant here).  */
@@ -3656,8 +3640,7 @@ parse_address_main (char **str, aarch64_opnd_info *operand,
 	    }
 
 	  /* #:<reloc_op>:  */
-	  if (! aarch64_get_expression (exp, &p, GE_NO_PREFIX, REJECT_ABSENT,
-					aarch64_force_reloc (ty) == 1))
+	  if (! aarch64_get_expression (exp, &p, GE_NO_PREFIX, REJECT_ABSENT))
 	    {
 	      set_syntax_error (_("invalid relocation expression"));
 	      return false;
@@ -3673,8 +3656,7 @@ parse_address_main (char **str, aarch64_opnd_info *operand,
 	    /* =immediate; need to generate the literal in the literal pool. */
 	    inst.gen_lit_pool = 1;
 
-	  if (!aarch64_get_expression (exp, &p, GE_NO_PREFIX, REJECT_ABSENT,
-				       NORMAL_RESOLUTION))
+	  if (!aarch64_get_expression (exp, &p, GE_NO_PREFIX, REJECT_ABSENT))
 	    {
 	      set_syntax_error (_("invalid address"));
 	      return false;
@@ -3780,8 +3762,7 @@ parse_address_main (char **str, aarch64_opnd_info *operand,
 	      /* We now have the group relocation table entry corresponding to
 	         the name in the assembler source.  Next, we parse the
 	         expression.  */
-	      if (! aarch64_get_expression (exp, &p, GE_NO_PREFIX, REJECT_ABSENT,
-					    aarch64_force_reloc (entry->ldst_type) == 1))
+	      if (! aarch64_get_expression (exp, &p, GE_NO_PREFIX, REJECT_ABSENT))
 		{
 		  set_syntax_error (_("invalid relocation expression"));
 		  return false;
@@ -3794,8 +3775,7 @@ parse_address_main (char **str, aarch64_opnd_info *operand,
 	    }
 	  else
 	    {
-	      if (! aarch64_get_expression (exp, &p, GE_OPT_PREFIX, REJECT_ABSENT,
-					    NORMAL_RESOLUTION))
+	      if (! aarch64_get_expression (exp, &p, GE_OPT_PREFIX, REJECT_ABSENT))
 		{
 		  set_syntax_error (_("invalid expression in the address"));
 		  return false;
@@ -3851,8 +3831,7 @@ parse_address_main (char **str, aarch64_opnd_info *operand,
 	  operand->addr.offset.regno = reg->number;
 	  operand->addr.offset.is_reg = 1;
 	}
-      else if (! aarch64_get_expression (exp, &p, GE_OPT_PREFIX, REJECT_ABSENT,
-					 NORMAL_RESOLUTION))
+      else if (! aarch64_get_expression (exp, &p, GE_OPT_PREFIX, REJECT_ABSENT))
 	{
 	  /* [Xn],#expr */
 	  set_syntax_error (_("invalid expression in the address"));
@@ -3980,8 +3959,7 @@ parse_half (char **str, int *internal_fixup_p)
   else
     *internal_fixup_p = 1;
 
-  if (! aarch64_get_expression (&inst.reloc.exp, &p, GE_NO_PREFIX, REJECT_ABSENT,
-				aarch64_force_reloc (inst.reloc.type) == 1))
+  if (! aarch64_get_expression (&inst.reloc.exp, &p, GE_NO_PREFIX, REJECT_ABSENT))
     return false;
 
   *str = p;
@@ -4023,8 +4001,7 @@ parse_adrp (char **str)
     inst.reloc.type = BFD_RELOC_AARCH64_ADR_HI21_PCREL;
 
   inst.reloc.pc_rel = 1;
-  if (! aarch64_get_expression (&inst.reloc.exp, &p, GE_NO_PREFIX, REJECT_ABSENT,
-				aarch64_force_reloc (inst.reloc.type) == 1))
+  if (! aarch64_get_expression (&inst.reloc.exp, &p, GE_NO_PREFIX, REJECT_ABSENT))
     return false;
   *str = p;
   return true;
@@ -6706,8 +6683,7 @@ parse_operands (char *str, const aarch64_opcode *opcode)
 	      goto failure;
 	    str = saved;
 	    po_misc_or_fail (aarch64_get_expression (&inst.reloc.exp, &str,
-						     GE_OPT_PREFIX, REJECT_ABSENT,
-						     NORMAL_RESOLUTION));
+						     GE_OPT_PREFIX, REJECT_ABSENT));
 	    /* The MOV immediate alias will be fixed up by fix_mov_imm_insn
 	       later.  fix_mov_imm_insn will try to determine a machine
 	       instruction (MOVZ, MOVN or ORR) for it and will issue an error
@@ -8834,7 +8810,8 @@ md_apply_fix (fixS * fixP, valueT * valP, segT seg)
 
   /* Note whether this will delete the relocation.  */
 
-  if (fixP->fx_addsy == 0 && !fixP->fx_pcrel)
+  if (fixP->fx_addsy == 0 && !fixP->fx_pcrel
+      && aarch64_force_reloc (fixP->fx_r_type) <= 0)
     fixP->fx_done = 1;
 
   /* Process the relocations.  */
diff --git a/gas/testsuite/gas/aarch64/pr27217.d b/gas/testsuite/gas/aarch64/pr27217.d
index abbc48717b..3397dfa248 100644
--- a/gas/testsuite/gas/aarch64/pr27217.d
+++ b/gas/testsuite/gas/aarch64/pr27217.d
@@ -7,9 +7,9 @@
 Disassembly of section \.text:
 
 0+000 <.*>:
-[ 	]+0:[ 	]+90000000[ 	]+adrp[ 	]+x0, 12345678[ 	]+<bar>
-[ 	]+0:[ 	]+R_AARCH64(|_P32)_ADR_PREL_PG_HI21[ 	]+bar
+[ 	]+0:[ 	]+90000000[ 	]+adrp[ 	]+x0, [0-9]*[ 	]+<.*>
+[ 	]+0:[ 	]+R_AARCH64(|_P32)_ADR_PREL_PG_HI21[ 	]+\*ABS\*\+0x12345678
 [ 	]+4:[ 	]+91000000[ 	]+add[ 	]+x0, x0, #0x0
-[ 	]+4:[ 	]+R_AARCH64(|_P32)_ADD_ABS_LO12_NC[ 	]+bar
+[ 	]+4:[ 	]+R_AARCH64(|_P32)_ADD_ABS_LO12_NC[ 	]+\*ABS\*\+0x12345678
 [ 	]+8:[ 	]+d65f03c0[ 	]+ret
 #pass