[PATCH 1/2] RISC-V: Stop generating mapping symbol $x, replace with $x<isa>.

[Nelson Chu]

The psABI defined $x to the architecture which is same as the file elf
attribute.  But GNU defined it to that is same as the previous $x<isa>,
and always generated $x<isa> at the begining of each section.  That is
because considering two objects have different architecture in their elf
attributes, then $x will always be wrong after linking since the merged
arch string will be changed.  For example, object A with rv32ic and object
B with rv32ia, $x from A is rv32ic and $x from B is rv32ia, but the final
output is rv32ica, so $x from A and B need to be updated to rv32ic and
rv32ia by linker respectively.  I think let linker to do this is not good,
so in order to follow the psABI, we will stop generating the $x for now.
Instead, all $x will be replaced with the corresponding $x<isa>.  The
dis-assembler will also treat $x like what psABI defined.
---
 gas/config/tc-riscv.c                     | 41 ++++++++++++++---------
 gas/testsuite/gas/riscv/mapping-symbols.d |  7 ++--
 2 files changed, 28 insertions(+), 20 deletions(-)

diff --git a/gas/config/tc-riscv.c b/gas/config/tc-riscv.c
index 493c393f5b2..ee3980f43f1 100644
--- a/gas/config/tc-riscv.c
+++ b/gas/config/tc-riscv.c
@@ -539,7 +539,12 @@ make_mapping_symbol (enum riscv_seg_mstate state,
 	  name = buff;
 	}
       else
-	name = "$x";
+	{
+	  /* The $x without isa shouldn't be generated since it will put more
+	     burden on the linker when linking objects with different isa.  */
+	  name = "$x";
+	  as_warn (_("The mapping symbol $x shouldn't be generated"));
+	}
       break;
     default:
       abort ();
@@ -585,11 +590,20 @@ make_mapping_symbol (enum riscv_seg_mstate state,
 
   if (odd_data_padding)
     {
-      /* If the removed mapping symbol is $x+arch, then add it back to
-	 the next $x.  */
-      const char *str = removed != NULL
-			&& strncmp (S_GET_NAME (removed), "$xrv", 4) == 0
-			? S_GET_NAME (removed) + 2 : NULL;
+      /* Search and find the previous $x+isa which in the same frag.  */
+      const char *str = NULL;
+      symbolS *p = symbol_previous (symbol);
+      for (; p != NULL; p = symbol_previous (p))
+	{
+	  if (symbol_get_frag (p) == frag
+	      && S_GET_NAME (p)
+	      && strncmp (S_GET_NAME (p), "$xrv", 4) == 0
+	      && S_GET_VALUE (p) <= S_GET_VALUE (symbol))
+	    {
+	      str = S_GET_NAME (p) + 2;
+	      break;
+	    }
+	}
       make_mapping_symbol (MAP_INSN, frag->fr_fix + 1, frag, str,
 			   false/* odd_data_padding */);
     }
@@ -607,7 +621,6 @@ riscv_mapping_state (enum riscv_seg_mstate to_state,
 {
   enum riscv_seg_mstate from_state =
 	seg_info (now_seg)->tc_segment_info_data.map_state;
-  bool reset_seg_arch_str = false;
 
   if (!SEG_NORMAL (now_seg)
       /* For now we only add the mapping symbols to text sections.
@@ -622,26 +635,22 @@ riscv_mapping_state (enum riscv_seg_mstate to_state,
   symbolS *seg_arch_symbol =
 	seg_info (now_seg)->tc_segment_info_data.arch_map_symbol;
   if (to_state == MAP_INSN && seg_arch_symbol == 0)
-    {
-      /* Always add $x+arch at the first instruction of section.  */
-      reset_seg_arch_str = true;
-    }
+    /* The first instruction of section.  */
+    ;
   else if (seg_arch_symbol != 0
 	   && to_state == MAP_INSN
 	   && !fr_align_code
 	   && strcmp (riscv_rps_as.subset_list->arch_str,
 		      S_GET_NAME (seg_arch_symbol) + 2) != 0)
-    {
-      reset_seg_arch_str = true;
-    }
+    /* Different architecture string.  */
+    ;
   else if (from_state == to_state)
     return;
 
   valueT value = (valueT) (frag_now_fix () - max_chars);
   seg_info (now_seg)->tc_segment_info_data.map_state = to_state;
   seg_info (now_seg)->tc_segment_info_data.last_insn16 = false;
-  const char *arch_str = reset_seg_arch_str
-			 ? riscv_rps_as.subset_list->arch_str : NULL;
+  const char *arch_str = riscv_rps_as.subset_list->arch_str;
   make_mapping_symbol (to_state, value, frag_now, arch_str,
 		       false/* odd_data_padding */);
 }
diff --git a/gas/testsuite/gas/riscv/mapping-symbols.d b/gas/testsuite/gas/riscv/mapping-symbols.d
index 057454bf991..ab1d4700e5f 100644
--- a/gas/testsuite/gas/riscv/mapping-symbols.d
+++ b/gas/testsuite/gas/riscv/mapping-symbols.d
@@ -20,14 +20,13 @@ SYMBOL TABLE:
 0+00 l    d  .text.odd.align.start.insn	0+00 .text.odd.align.start.insn
 0+00 l       .text.odd.align.start.insn	0+00 \$xrv32i2p1_c2p0
 0+02 l       .text.odd.align.start.insn	0+00 \$d
-0+08 l       .text.odd.align.start.insn	0+00 \$xrv32i2p1
 0+00 l    d  .text.odd.align.start.data	0+00 .text.odd.align.start.data
 0+00 l       .text.odd.align.start.data	0+00 \$d
 0+00 l    d  .text.zero.fill.first	0+00 .text.zero.fill.first
 0+00 l       .text.zero.fill.first	0+00 \$xrv32i2p1_c2p0
 0+00 l    d  .text.zero.fill.last	0+00 .text.zero.fill.last
 0+00 l       .text.zero.fill.last	0+00 \$xrv32i2p1_c2p0
-0+02 l       .text.zero.fill.last	0+00 \$x
+0+02 l       .text.zero.fill.last	0+00 \$xrv32i2p1_c2p0
 0+00 l    d  .text.zero.fill.align.A	0+00 .text.zero.fill.align.A
 0+00 l       .text.zero.fill.align.A	0+00 \$xrv32i2p1_c2p0
 0+00 l    d  .text.zero.fill.align.B	0+00 .text.zero.fill.align.B
@@ -42,9 +41,9 @@ SYMBOL TABLE:
 0+00 l    d  .text.relax.align	0+00 .text.relax.align
 0+00 l       .text.relax.align	0+00 \$xrv32i2p1_c2p0
 0+08 l       .text.relax.align	0+00 \$xrv32i2p1
-0+0a l       .text.section.padding	0+00 \$x
+0+0a l       .text.section.padding	0+00 \$xrv32i2p1_c2p0
 0+03 l       .text.odd.align.start.insn	0+00 \$d
-0+04 l       .text.odd.align.start.insn	0+00 \$x
+0+04 l       .text.odd.align.start.insn	0+00 \$xrv32i2p1
 0+01 l       .text.odd.align.start.data	0+00 \$d
 0+02 l       .text.odd.align.start.data	0+00 \$xrv32i2p1_c2p0
 0+00 l    d  .riscv.attributes	0+00 .riscv.attributes
-- 
2.39.3 (Apple Git-146)