[PATCH] riscv/disas: Fix disas output of upper immediates

[Christoph Muellner]

From: Christoph Müllner <christoph.muellner@vrull.eu>

The GNU assembler produces the following output for instructions
with upper immediates:
    00002597                auipc   a1,0x2
    000024b7                lui     s1,0x2
    6409                    lui     s0,0x2 # c.lui

The immediate operands of upper immediates are not shifted.

However, the QEMU disassembler prints them shifted:
    00002597          auipc                   a1,8192
    000024b7          lui                     s1,8192
    6409              lui                     s0,8192 # c.lui

The current implementation extracts the immediate bits and shifts the by 12,
so the internal representation of the immediate is the actual immediate.
However, the immediates are later printed using rv_fmt_rd_imm or
rv_fmt_rd_offset, which don't undo the shift.

Let's fix this by using specific output formats for instructions
with upper immediates, that take care of the shift.

Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>
---
 disas/riscv.c | 19 ++++++++++++++++---
 disas/riscv.h |  2 ++
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/disas/riscv.c b/disas/riscv.c
index cd7b6e86a7..3873a69157 100644
--- a/disas/riscv.c
+++ b/disas/riscv.c
@@ -1135,8 +1135,8 @@ static const rv_comp_data rvcp_fsgnjx_q[] = {
 
 const rv_opcode_data rvi_opcode_data[] = {
     { "illegal", rv_codec_illegal, rv_fmt_none, NULL, 0, 0, 0 },
-    { "lui", rv_codec_u, rv_fmt_rd_imm, NULL, 0, 0, 0 },
-    { "auipc", rv_codec_u, rv_fmt_rd_offset, NULL, 0, 0, 0 },
+    { "lui", rv_codec_u, rv_fmt_rd_uimm, NULL, 0, 0, 0 },
+    { "auipc", rv_codec_u, rv_fmt_rd_uoffset, NULL, 0, 0, 0 },
     { "jal", rv_codec_uj, rv_fmt_rd_offset, rvcp_jal, 0, 0, 0 },
     { "jalr", rv_codec_i, rv_fmt_rd_rs1_offset, rvcp_jalr, 0, 0, 0 },
     { "beq", rv_codec_sb, rv_fmt_rs1_rs2_offset, rvcp_beq, 0, 0, 0 },
@@ -1382,7 +1382,7 @@ const rv_opcode_data rvi_opcode_data[] = {
       rv_op_addi },
     { "c.addi16sp", rv_codec_ci_16sp, rv_fmt_rd_rs1_imm, NULL, rv_op_addi,
       rv_op_addi, rv_op_addi, rvcd_imm_nz },
-    { "c.lui", rv_codec_ci_lui, rv_fmt_rd_imm, NULL, rv_op_lui, rv_op_lui,
+    { "c.lui", rv_codec_ci_lui, rv_fmt_rd_uimm, NULL, rv_op_lui, rv_op_lui,
       rv_op_lui, rvcd_imm_nz },
     { "c.srli", rv_codec_cb_sh6, rv_fmt_rd_rs1_imm, NULL, rv_op_srli,
       rv_op_srli, rv_op_srli, rvcd_imm_nz },
@@ -4694,6 +4694,19 @@ static void format_inst(char *buf, size_t buflen, size_t 
tab, rv_decode *dec)
                 dec->pc + dec->imm);
             append(buf, tmp, buflen);
             break;
+        case 'U':
+            fmt++;
+            snprintf(tmp, sizeof(tmp), "%d", dec->imm >> 12);
+            append(buf, tmp, buflen);
+            if (*fmt == 'o') {
+                while (strlen(buf) < tab * 2) {
+                    append(buf, " ", buflen);
+                }
+                snprintf(tmp, sizeof(tmp), "# 0x%" PRIx64,
+                    dec->pc + dec->imm);
+                append(buf, tmp, buflen);
+            }
+            break;
         case 'c': {
             const char *name = csr_name(dec->imm & 0xfff);
             if (name) {
diff --git a/disas/riscv.h b/disas/riscv.h
index 9cf901fc1e..8abb578b51 100644
--- a/disas/riscv.h
+++ b/disas/riscv.h
@@ -227,7 +227,9 @@ enum {
 #define rv_fmt_pred_succ              "O\tp,s"
 #define rv_fmt_rs1_rs2                "O\t1,2"
 #define rv_fmt_rd_imm                 "O\t0,i"
+#define rv_fmt_rd_uimm                "O\t0,Ui"
 #define rv_fmt_rd_offset              "O\t0,o"
+#define rv_fmt_rd_uoffset             "O\t0,Uo"
 #define rv_fmt_rd_rs1_rs2             "O\t0,1,2"
 #define rv_fmt_frd_rs1                "O\t3,1"
 #define rv_fmt_frd_rs1_rs2            "O\t3,1,2"
-- 
2.41.0