RISC-V: Fix .option arch compatibility with zc*

This fixes an issue whereby .option arch with the zc extensions can
result in gas refusing to accept otherwise valid instructions because
the base C extension is not enabled.

gas/config/tc-riscv.c

@@ -5126,6 +5126,8 @@ s_riscv_option (int x ATTRIBUTE_UNUSED)
       riscv_update_subset (&riscv_rps_as, "-c");
       riscv_reset_subsets_list_arch_str ();
       riscv_set_rvc (false);
+      if (riscv_subset_supports (&riscv_rps_as, "zca"))
+	riscv_set_rvc (true);
     }
   else if (strcmp (name, "pic") == 0)
     riscv_opts.pic = true;

gas/testsuite/gas/riscv/zc-zca-option-march.d

@@ -0,0 +1,12 @@
+#as: -march=rv32i
+#source: zc-zca-option-march.s
+#objdump: -d -Mno-aliases
+
+.*:[ 	]+file format .*
+
+
+Disassembly of section .text:
+
+0+000 <testcase>:
+[ 	]+0:[ 	]+0001[ 	]+c.addi[ 	]+zero,0
+#...

gas/testsuite/gas/riscv/zc-zca-option-march.s

@@ -0,0 +1,6 @@
+	.attribute 5, "rv32i"
+    .option rvc
+	.option arch, +zca
+    .option norvc
+testcase:
+	c.nop

gas/testsuite/gas/riscv/zc-zcmt-emit-jal-relax.s

@@ -0,0 +1,46 @@
+.macro PADDIING_32_BYTES
+	.option push
+	.option arch, -zcmt
+	.option arch, -zca
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	.option pop
+.endm
+
+.macro PADDIING_256_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+.endm
+
+.macro PADDIING_2048_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+.endm
+
+.option relax
+target:
+	c.bnez s0, target
+	jal Far
+	c.bnez s0, Far
+	PADDIING_2048_BYTES
+	PADDIING_2048_BYTES
+Far:
+	ret

gas/testsuite/gas/riscv/zc-zcmt-relax-c-branch.s

@@ -0,0 +1,50 @@
+.macro PADDIING_32_BYTES
+	.option push
+	.option arch, -zcmt
+	.option arch, -zca
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	.option pop
+.endm
+
+.macro PADDIING_256_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+	PADDIING_32_BYTES
+.endm
+
+.macro PADDIING_2048_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+	PADDIING_256_BYTES
+.endm
+
+.option norelax
+target:
+	c.beqz s0, C_BRANCH_RANGE
+C_BRANCH_RANGE:
+	c.bnez s0, EXPAND_TO_BRANCH
+	PADDIING_256_BYTES
+EXPAND_TO_BRANCH:
+	c.bnez s0, FLIP_C_BRANCH_AND_JUMP
+	PADDIING_2048_BYTES
+	PADDIING_2048_BYTES
+FLIP_C_BRANCH_AND_JUMP:
+	c.beqz s0, -4
+	ret