From: Richard Henderson <richard.henderson@linaro.org>

Cc: qemu-stable@nongnu.org
Fixes: b3e22b2318a ("target/i386: add core of new i386 decoder")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2495
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Link: https://lore.kernel.org/r/20240812025844.58956-2-richard.henderson@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 416f2b16c02c618c0f233372ebfe343f9ee667d4)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/target/i386/tcg/decode-new.c.inc b/target/i386/tcg/decode-new.c.inc
index ffd3a42688..852579eef5 100644
--- a/target/i386/tcg/decode-new.c.inc
+++ b/target/i386/tcg/decode-new.c.inc
@@ -1237,7 +1237,10 @@ static bool decode_op(DisasContext *s, CPUX86State *env, X86DecodedInsn *decode,
             op->unit = X86_OP_SSE;
         }
     get_reg:
-        op->n = ((get_modrm(s, env) >> 3) & 7) | REX_R(s);
+        op->n = ((get_modrm(s, env) >> 3) & 7);
+        if (op->unit != X86_OP_MMX) {
+            op->n |= REX_R(s);
+        }
         break;
 
     case X86_TYPE_E:  /* ALU modrm operand */
-- 
2.39.2