From 8572c15973e34f0c05dee4a81ec37bbc4bd826b5 Mon Sep 17 00:00:00 2001
From: Alexis Engelke <alexis.engelke@googlemail.com>
Date: Mon, 10 Feb 2020 20:33:00 +0100
Subject: [PATCH] Handle RVMR encodings correctly in 32-bit mode

The most significant bit in the immediate is ingored in 32-bit mode.
---
 decode.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/decode.c b/decode.c
index 6a21d9d..1f2e15f 100644
--- a/decode.c
+++ b/decode.c
@@ -536,9 +536,24 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
 #endif
         off += addr_size;
     }
+    else if (UNLIKELY(imm_control == 5))
+    {
+        FdOp* operand = &instr->operands[DESC_IMM_IDX(desc)];
+        operand->type = FD_OT_REG;
+
+        if (UNLIKELY(off + 1 > len))
+            return FD_ERR_PARTIAL;
+        uint8_t reg = (uint8_t) LOAD_LE_1(&buffer[off]);
+        off += 1;
+
+        if (mode == DECODE_32)
+            reg &= 0x7f;
+        operand->reg = reg >> 4;
+    }
     else if (imm_control != 0)
     {
         FdOp* operand = &instr->operands[DESC_IMM_IDX(desc)];
+        operand->type = FD_OT_IMM;
 
         uint8_t imm_size;
         if (DESC_IMM_BYTE(desc))
@@ -588,16 +603,6 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
                 operand->size = 8;
 #endif
         }
-
-        if (UNLIKELY(imm_control == 5))
-        {
-            operand->type = FD_OT_REG;
-            operand->reg = (instr->imm & 0xf0) >> 4;
-        }
-        else
-        {
-            operand->type = FD_OT_IMM;
-        }
     }
 
     if ((prefixes & PREFIX_LOCK) && !desc->lock)