[Qemu-devel] [RFC PATCH v4 23/75] target/i386: introduce operands for decoding modrm fields

[Jan Bobek]

The old code uses bitshifts and bitwise-and all over the place for
decoding ModR/M fields. Avoid doing that by introducing proper
decoding operands.

Signed-off-by: Jan Bobek <address@hidden>
---
 target/i386/translate.c | 62 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/target/i386/translate.c b/target/i386/translate.c
index a0a9f64ff3..b3b316d389 100644
--- a/target/i386/translate.c
+++ b/target/i386/translate.c
@@ -4791,6 +4791,68 @@ INSNOP_FINALIZE(modrm)
 {
 }
 
+/*
+ * modrm_mod
+ *
+ * Operand whose value is the MOD field of the ModR/M byte.
+ */
+typedef int insnop_arg_t(modrm_mod);
+typedef struct {} insnop_ctxt_t(modrm_mod);
+
+INSNOP_INIT(modrm_mod)
+{
+    return true;
+}
+INSNOP_PREPARE(modrm_mod)
+{
+    return (modrm >> 6) & 3;
+}
+INSNOP_FINALIZE(modrm_mod)
+{
+}
+
+/*
+ * modrm_reg
+ *
+ * Operand whose value is the REG field of the ModR/M byte, extended
+ * with the REX.R bit if REX prefix is present.
+ */
+typedef int insnop_arg_t(modrm_reg);
+typedef struct {} insnop_ctxt_t(modrm_reg);
+
+INSNOP_INIT(modrm_reg)
+{
+    return true;
+}
+INSNOP_PREPARE(modrm_reg)
+{
+    return ((modrm >> 3) & 7) | REX_R(s);
+}
+INSNOP_FINALIZE(modrm_reg)
+{
+}
+
+/*
+ * modrm_rm
+ *
+ * Operand whose value is the RM field of the ModR/M byte, extended
+ * with the REX.B bit if REX prefix is present.
+ */
+typedef int insnop_arg_t(modrm_rm);
+typedef struct {} insnop_ctxt_t(modrm_rm);
+
+INSNOP_INIT(modrm_rm)
+{
+    return true;
+}
+INSNOP_PREPARE(modrm_rm)
+{
+    return (modrm & 7) | REX_B(s);
+}
+INSNOP_FINALIZE(modrm_rm)
+{
+}
+
 static void gen_sse_ng(CPUX86State *env, DisasContext *s, int b)
 {
     enum {
-- 
2.20.1