[PATCH] RISC-V: Allow ISA subsets to be disabled

[Palmer Dabbelt <palmer@dabbelt.com>]

Without this patch, passing "-march=rv64ic -march=rv64i" results in
you getting a "RV64IC" toolchain, which isn't expected.

gas/ChangeLog:

2017-03-30  Palmer Dabbelt  <palmer@dabbelt.com>

       * config/tc-riscv.c (riscv_clear_subsets): New function.
       (riscv_add_subset): Call riscv_clear_subsets and riscv_set_rvc to
       clear RVC when it's been previously set.
---
 gas/ChangeLog         |  6 ++++++
 gas/config/tc-riscv.c | 15 +++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/gas/ChangeLog b/gas/ChangeLog
index a5c1d08..6f419f7 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,9 @@
+2017-03-30  Palmer Dabbelt  <palmer@dabbelt.com>
+
+	* config/tc-riscv.c (riscv_clear_subsets): New function.
+	(riscv_add_subset): Call riscv_clear_subsets and riscv_set_rvc to
+	clear RVC when it's been previously set.
+
 2017-03-30  Pip Cet  <pipcet@gmail.com>
 
 	* config/tc-wasm32.h: New file: Add WebAssembly assembler target.
diff --git a/gas/config/tc-riscv.c b/gas/config/tc-riscv.c
index 68b28f7..2830ba1 100644
--- a/gas/config/tc-riscv.c
+++ b/gas/config/tc-riscv.c
@@ -121,6 +121,18 @@ riscv_subset_supports (const char *feature)
 }
 
 static void
+riscv_clear_subsets (void)
+{
+  while (riscv_subsets != NULL)
+    {
+      struct riscv_subset *next = riscv_subsets->next;
+      free (riscv_subsets->name);
+      free (riscv_subsets);
+      riscv_subsets = next;
+    }
+}
+
+static void
 riscv_add_subset (const char *subset)
 {
   struct riscv_subset *s = xmalloc (sizeof *s);
@@ -139,6 +151,8 @@ riscv_set_arch (const char *s)
   const char *extension = NULL;
   const char *p = s;
 
+  riscv_clear_subsets();
+
   if (strncmp (p, "rv32", 4) == 0)
     {
       xlen = 32;
@@ -1808,6 +1822,7 @@ riscv_after_parse_args (void)
     riscv_set_arch (xlen == 64 ? "rv64g" : "rv32g");
 
   /* Add the RVC extension, regardless of -march, to support .option rvc.  */
+  riscv_set_rvc (FALSE);
   if (riscv_subset_supports ("c"))
     riscv_set_rvc (TRUE);
   else
-- 
2.10.2