target/riscv: fix shifts shamt value for rv128c

For rv128c shifts, a shamt of 0 is a shamt of 64, while for rv32c/rv64c
it stays 0 and is a hint instruction that does not change processor state.
For rv128c right shifts, the 6-bit shamt is in addition sign extended to
7 bits.

Signed-off-by: Frédéric Pétrot <frederic.petrot@univ-grenoble-alpes.fr>
Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220710110451.245567-1-frederic.petrot@univ-grenoble-alpes.fr>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

disas/riscv.c

@@ -2402,10 +2402,25 @@ static int32_t operand_sbimm12(rv_inst inst)
         ((inst << 56) >> 63) << 11;
 }
 
-static uint32_t operand_cimmsh6(rv_inst inst)
+static uint32_t operand_cimmshl6(rv_inst inst, rv_isa isa)
 {
-    return ((inst << 51) >> 63) << 5 |
+    int imm = ((inst << 51) >> 63) << 5 |
         (inst << 57) >> 59;
+    if (isa == rv128) {
+        imm = imm ? imm : 64;
+    }
+    return imm;
+}
+
+static uint32_t operand_cimmshr6(rv_inst inst, rv_isa isa)
+{
+    int imm = ((inst << 51) >> 63) << 5 |
+        (inst << 57) >> 59;
+    if (isa == rv128) {
+        imm = imm | (imm & 32) << 1;
+        imm = imm ? imm : 64;
+    }
+    return imm;
 }
 
 static int32_t operand_cimmi(rv_inst inst)
@@ -2529,7 +2544,7 @@ static uint32_t operand_rnum(rv_inst inst)
 
 /* decode operands */
 
-static void decode_inst_operands(rv_decode *dec)
+static void decode_inst_operands(rv_decode *dec, rv_isa isa)
 {
     rv_inst inst = dec->inst;
     dec->codec = opcode_data[dec->op].codec;
@@ -2652,7 +2667,7 @@ static void decode_inst_operands(rv_decode *dec)
     case rv_codec_cb_sh6:
         dec->rd = dec->rs1 = operand_crs1rdq(inst) + 8;
         dec->rs2 = rv_ireg_zero;
-        dec->imm = operand_cimmsh6(inst);
+        dec->imm = operand_cimmshr6(inst, isa);
         break;
     case rv_codec_ci:
         dec->rd = dec->rs1 = operand_crs1rd(inst);
@@ -2667,7 +2682,7 @@ static void decode_inst_operands(rv_decode *dec)
     case rv_codec_ci_sh6:
         dec->rd = dec->rs1 = operand_crs1rd(inst);
         dec->rs2 = rv_ireg_zero;
-        dec->imm = operand_cimmsh6(inst);
+        dec->imm = operand_cimmshl6(inst, isa);
         break;
     case rv_codec_ci_16sp:
         dec->rd = rv_ireg_sp;
@@ -3193,7 +3208,7 @@ disasm_inst(char *buf, size_t buflen, rv_isa isa, uint64_t pc, rv_inst inst)
     dec.pc = pc;
     dec.inst = inst;
     decode_inst_opcode(&dec, isa);
-    decode_inst_operands(&dec);
+    decode_inst_operands(&dec, isa);
     decode_inst_decompress(&dec, isa);
     decode_inst_lift_pseudo(&dec);
     format_inst(buf, buflen, 16, &dec);

target/riscv/insn16.decode

@@ -31,7 +31,8 @@
 %imm_cb        12:s1 5:2 2:1 10:2 3:2 !function=ex_shift_1
 %imm_cj        12:s1 8:1 9:2 6:1 7:1 2:1 11:1 3:3 !function=ex_shift_1
 
-%shimm_6bit   12:1 2:5               !function=ex_rvc_shifti
+%shlimm_6bit  12:1 2:5               !function=ex_rvc_shiftli
+%shrimm_6bit  12:1 2:5               !function=ex_rvc_shiftri
 %uimm_6bit_lq 2:4 12:1 6:1           !function=ex_shift_4
 %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
@@ -82,9 +83,9 @@
 @c_addi16sp     ... .  ..... ..... .. &i imm=%imm_addi16sp rs1=2 rd=2
 
 @c_shift        ... . .. ... ..... .. \
-                &shift rd=%rs1_3 rs1=%rs1_3 shamt=%shimm_6bit
+                &shift rd=%rs1_3 rs1=%rs1_3 shamt=%shrimm_6bit
 @c_shift2       ... . .. ... ..... .. \
-                &shift rd=%rd rs1=%rd shamt=%shimm_6bit
+                &shift rd=%rd rs1=%rd shamt=%shlimm_6bit
 
 @c_andi         ... . .. ... ..... .. &i imm=%imm_ci rs1=%rs1_3 rd=%rs1_3
 

target/riscv/translate.c

@@ -705,10 +705,26 @@ static int ex_rvc_register(DisasContext *ctx, int reg)
     return 8 + reg;
 }
 
-static int ex_rvc_shifti(DisasContext *ctx, int imm)
+static int ex_rvc_shiftli(DisasContext *ctx, int imm)
 {
     /* For RV128 a shamt of 0 means a shift by 64. */
-    return imm ? imm : 64;
+    if (get_ol(ctx) == MXL_RV128) {
+        imm = imm ? imm : 64;
+    }
+    return imm;
+}
+
+static int ex_rvc_shiftri(DisasContext *ctx, int imm)
+{
+    /*
+     * For RV128 a shamt of 0 means a shift by 64, furthermore, for right
+     * shifts, the shamt is sign-extended.
+     */
+    if (get_ol(ctx) == MXL_RV128) {
+        imm = imm | (imm & 32) << 1;
+        imm = imm ? imm : 64;
+    }
+    return imm;
 }
 
 /* Include the auto-generated decoder for 32 bit insn */