Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
---
 target/riscv/insn16-32.decode | 24 ++++++++++++++++++++++++
 target/riscv/insn16-64.decode | 31 +++++++++++++++++++++++++++++++
 target/riscv/translate.c      | 18 +++++++++++++++++-
 target/riscv/meson.build      |  7 +++++--
 4 files changed, 77 insertions(+), 3 deletions(-)

diff --git a/target/riscv/insn16-32.decode b/target/riscv/insn16-32.decode
index 0819b17028..f83f43e955 100644
--- a/target/riscv/insn16-32.decode
+++ b/target/riscv/insn16-32.decode
@@ -16,6 +16,30 @@
 # You should have received a copy of the GNU General Public License along with
 # this program.  If not, see <http://www.gnu.org/licenses/>.
 
+# Fields imported from insn16.decode:
+%rd        7:5
+%rs1_3     7:3                !function=ex_rvc_register
+%rs2_3     2:3                !function=ex_rvc_register
+%rs2_5     2:5
+
+# Immediates imported from insn16.decode:
+%uimm_cl_w     5:1 10:3 6:1       !function=ex_shift_2
+%uimm_6bit_lw 2:2 12:1 4:3           !function=ex_shift_2
+%uimm_6bit_sw 7:2 9:4                !function=ex_shift_2
+%imm_cj        12:s1 8:1 9:2 6:1 7:1 2:1 11:1 3:3 !function=ex_shift_1
+
+# Argument sets imported from insn16.decode:
+&j         imm rd       !extern
+&i         imm rs1 rd   !extern
+&s         imm rs1 rs2  !extern
+
+# Formats 16 imported from insn16.decode:
+@cl_w      ... ... ... .. ... .. &i      imm=%uimm_cl_w   rs1=%rs1_3  rd=%rs2_3
+@cj        ...    ........... .. &j      imm=%imm_cj
+@c_lwsp    ... . .....  ..... .. &i      imm=%uimm_6bit_lw rs1=2 %rd
+@c_swsp    ... . .....  ..... .. &s      imm=%uimm_6bit_sw rs1=2 rs2=%rs2_5
+@cs_w      ... ... ... .. ... .. &s      imm=%uimm_cl_w   rs1=%rs1_3  rs2=%rs2_3
+
 # *** RV32C Standard Extension (Quadrant 0) ***
 flw               011  ... ... .. ... 00 @cl_w
 fsw               111  ... ... .. ... 00 @cs_w
diff --git a/target/riscv/insn16-64.decode b/target/riscv/insn16-64.decode
index 672e1e916f..dbef1e5365 100644
--- a/target/riscv/insn16-64.decode
+++ b/target/riscv/insn16-64.decode
@@ -16,6 +16,37 @@
 # You should have received a copy of the GNU General Public License along with
 # this program.  If not, see <http://www.gnu.org/licenses/>.
 
+# Fields imported from insn16.decode:
+%rd        7:5
+%rs1_3     7:3                !function=ex_rvc_register
+%rs2_3     2:3                !function=ex_rvc_register
+%rs2_5     2:5
+
+# Immediates imported from insn16.decode:
+%imm_ci        12:s1 2:5
+%uimm_cl_d     5:2 10:3           !function=ex_shift_3
+%uimm_6bit_ld 2:3 12:1 5:2           !function=ex_shift_3
+%uimm_6bit_lw 2:2 12:1 4:3           !function=ex_shift_2
+%uimm_6bit_sd 7:3 10:3               !function=ex_shift_3
+
+# Argument sets imported from insn16.decode:
+&empty                  !extern
+&r         rd rs1 rs2   !extern
+&i         imm rs1 rd   !extern
+&s         imm rs1 rs2  !extern
+&j         imm rd       !extern
+&b         imm rs2 rs1  !extern
+&u         imm rd       !extern
+&shift     shamt rs1 rd !extern
+
+# Formats 16 imported from insn16.decode:
+@ci        ... . ..... .....  .. &i      imm=%imm_ci      rs1=%rd     %rd
+@cl_d      ... ... ... .. ... .. &i      imm=%uimm_cl_d   rs1=%rs1_3  rd=%rs2_3
+@cs_d      ... ... ... .. ... .. &s      imm=%uimm_cl_d   rs1=%rs1_3  rs2=%rs2_3
+@cs_2      ... ... ... .. ... .. &r      rs2=%rs2_3       rs1=%rs1_3  rd=%rs1_3
+@c_ldsp    ... . .....  ..... .. &i      imm=%uimm_6bit_ld rs1=2 %rd
+@c_sdsp    ... . .....  ..... .. &s      imm=%uimm_6bit_sd rs1=2 rs2=%rs2_5
+
 # *** RV64C Standard Extension (Quadrant 0) ***
 ld                011  ... ... .. ... 00 @cl_d
 sd                111  ... ... .. ... 00 @cs_d
diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index 4af55deaea..9a93c77fd6 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -602,6 +602,10 @@ static uint32_t opcode_at(DisasContextBase *dcbase, target_ulong pc)
 
 /* Include the auto-generated decoder for 16 bit insn */
 #include "decode-insn16.c.inc"
+#include "decode-insn16-32.c.inc"
+#ifdef TARGET_RISCV64
+# include "decode-insn16-64.c.inc"
+#endif
 
 static void decode_opc(CPURISCVState *env, DisasContext *ctx, uint16_t opcode)
 {
@@ -612,7 +616,19 @@ static void decode_opc(CPURISCVState *env, DisasContext *ctx, uint16_t opcode)
         } else {
             ctx->pc_succ_insn = ctx->base.pc_next + 2;
             if (!decode_insn16(ctx, opcode)) {
-                gen_exception_illegal(ctx);
+                if (riscv_cpu_is_32bit(env)) {
+                    if (!decode_insn16_32(ctx, opcode)) {
+                        gen_exception_illegal(ctx);
+                    }
+                } else {
+#ifdef TARGET_RISCV64
+                    if (!decode_insn16_64(ctx, opcode)) {
+                        gen_exception_illegal(ctx);
+                    }
+#else
+                    gen_exception_illegal(ctx);
+#endif
+                }
             }
         }
     } else {
diff --git a/target/riscv/meson.build b/target/riscv/meson.build
index 88ab850682..d17b478120 100644
--- a/target/riscv/meson.build
+++ b/target/riscv/meson.build
@@ -1,12 +1,15 @@
 # FIXME extra_args should accept files()
 dir = meson.current_source_dir()
 gen32 = [
-  decodetree.process('insn16.decode', extra_args: [dir / 'insn16-32.decode', '--static-decode=decode_insn16', '--insnwidth=16']),
+  decodetree.process('insn16.decode', extra_args: ['--static-decode=decode_insn16', '--insnwidth=16']),
+  decodetree.process('insn16-32.decode', extra_args: ['--static-decode=decode_insn16_32', '--insnwidth=16']),
   decodetree.process('insn32.decode', extra_args: '--static-decode=decode_insn32'),
 ]
 
 gen64 = [
-  decodetree.process('insn16.decode', extra_args: [dir / 'insn16-64.decode', '--static-decode=decode_insn16', '--insnwidth=16']),
+  decodetree.process('insn16.decode', extra_args: ['--static-decode=decode_insn16', '--insnwidth=16']),
+  decodetree.process('insn16-32.decode', extra_args: ['--static-decode=decode_insn16_32', '--insnwidth=16']),
+  decodetree.process('insn16-64.decode', extra_args: ['--static-decode=decode_insn16_64', '--insnwidth=16']),
   decodetree.process('insn32.decode', extra_args: [dir / 'insn32-64.decode', '--static-decode=decode_insn32']),
 ]
 
-- 
2.31.0

On 4/2/21 1:03 PM, Alistair Francis wrote:
> Signed-off-by: Alistair Francis<alistair.francis@wdc.com>
> ---
>   target/riscv/insn16-32.decode | 24 ++++++++++++++++++++++++
>   target/riscv/insn16-64.decode | 31 +++++++++++++++++++++++++++++++
>   target/riscv/translate.c      | 18 +++++++++++++++++-
>   target/riscv/meson.build      |  7 +++++--
>   4 files changed, 77 insertions(+), 3 deletions(-)

Having these split out from the main decode file was a cool trick when we were 
sure that we never needed to support both.  Now, I think it would be better to 
merge the patterns back in to the main insn16.decode file.

You'd begin by adding a REQUIRE_64BIT(ctx) macro, much like the other REQUIRE 
macros in translate.c, using the translate-local is_32bit() function as 
discussed earlier.

You add this to all of the trans_* functions that are currently #ifdef 
TARGET_RISCV64, and merge the insn32-64.decode bits in first.

There may well be an issue of missing helper functions, particularly when it 
comes to RVF/RVD/RVV.  There's a suggestion that I made for Claudio for i386 
that may help here:

https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg08595.html

where you add stubs that allow the gen_helper_foo() function to be declared, 
insist that it be optimized away, and reduce to an abort with -O0.

Only after insn32.decode is complete, do insn16.decode.  That's because many of 
the insns here will need the REQUIRE_64BIT in place for correctness.

E.g.

{
   ld          011  ... ... .. ... 00 @cl_d
   flw         011  ... ... .. ... 00 @cl_w
}

Since ld already has REQUIRE_64BIT, for is_32bit it returns false, and we fall 
into the flw code.

There will be one extra helper required, when the 64-bit RVC insn has a set of 
illegal operands:

static bool trans_c64_illegal(DisasContext *ctx, arg_empty *a)
{
     REQUIRE_64BIT(ctx);
     return trans_illegal(ctx, a);
}

for use with quadrant 1:

{
   c64_illegal 001 -  00000  ----- 01 # c.addiw, RES rd=0
   addiw       001 .  .....  ..... 01 @ci
   jal         001     ........... 01 @cj    rd=1  # C.JAL

}

and quadrant 2:

{
   c64_illegal 011 -  00000  ----- 10 # c.ldsp, RES rd=0
   ld          011 .  .....  ..... 10 @c_ldsp
   flw         011 .  .....  ..... 10 @c_lwsp
}


r~