[PULL 27/53] target/i386: validate SSE prefixes directly in the decoding table

[Paolo Bonzini]

Many SSE and AVX instructions are only valid with specific prefixes
(none, 66, F3, F2).  Introduce a direct way to encode this in the
decoding table to avoid using decode groups too much.

Reviewed-by: Richard Henderson <richard.hender...@linaro.org>
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
 target/i386/tcg/decode-new.c.inc | 37 ++++++++++++++++++++++++++++++++
 target/i386/tcg/decode-new.h     |  1 +
 2 files changed, 38 insertions(+)

diff --git a/target/i386/tcg/decode-new.c.inc b/target/i386/tcg/decode-new.c.inc
index a7af673df3..64bef76159 100644
--- a/target/i386/tcg/decode-new.c.inc
+++ b/target/i386/tcg/decode-new.c.inc
@@ -110,6 +110,22 @@
 
 #define avx2_256 .vex_special = X86_VEX_AVX2_256,
 
+#define P_00          1
+#define P_66          (1 << PREFIX_DATA)
+#define P_F3          (1 << PREFIX_REPZ)
+#define P_F2          (1 << PREFIX_REPNZ)
+
+#define p_00          .valid_prefix = P_00,
+#define p_66          .valid_prefix = P_66,
+#define p_f3          .valid_prefix = P_F3,
+#define p_f2          .valid_prefix = P_F2,
+#define p_00_66       .valid_prefix = P_00 | P_66,
+#define p_00_f3       .valid_prefix = P_00 | P_F3,
+#define p_66_f2       .valid_prefix = P_66 | P_F2,
+#define p_00_66_f3    .valid_prefix = P_00 | P_66 | P_F3,
+#define p_66_f3_f2    .valid_prefix = P_66 | P_F3 | P_F2,
+#define p_00_66_f3_f2 .valid_prefix = P_00 | P_66 | P_F3 | P_F2,
+
 static uint8_t get_modrm(DisasContext *s, CPUX86State *env)
 {
     if (!s->has_modrm) {
@@ -480,6 +496,23 @@ static bool decode_op(DisasContext *s, CPUX86State *env, 
X86DecodedInsn *decode,
     return true;
 }
 
+static bool validate_sse_prefix(DisasContext *s, X86OpEntry *e)
+{
+    uint16_t sse_prefixes;
+
+    if (!e->valid_prefix) {
+        return true;
+    }
+    if (s->prefix & (PREFIX_REPZ | PREFIX_REPNZ)) {
+        /* In SSE instructions, 0xF3 and 0xF2 cancel 0x66.  */
+        s->prefix &= ~PREFIX_DATA;
+    }
+
+    /* Now, either zero or one bit is set in sse_prefixes.  */
+    sse_prefixes = s->prefix & (PREFIX_REPZ | PREFIX_REPNZ | PREFIX_DATA);
+    return e->valid_prefix & (1 << sse_prefixes);
+}
+
 static bool decode_insn(DisasContext *s, CPUX86State *env, X86DecodeFunc 
decode_func,
                         X86DecodedInsn *decode)
 {
@@ -491,6 +524,10 @@ static bool decode_insn(DisasContext *s, CPUX86State *env, 
X86DecodeFunc decode_
         e->decode(s, env, e, &decode->b);
     }
 
+    if (!validate_sse_prefix(s, e)) {
+        return false;
+    }
+
     /* First compute size of operands in order to initialize s->rip_offset.  */
     if (e->op0 != X86_TYPE_None) {
         if (!decode_op_size(s, e, e->s0, &decode->op[0].ot)) {
diff --git a/target/i386/tcg/decode-new.h b/target/i386/tcg/decode-new.h
index 25e5400a8a..8456ae67ad 100644
--- a/target/i386/tcg/decode-new.h
+++ b/target/i386/tcg/decode-new.h
@@ -212,6 +212,7 @@ struct X86OpEntry {
     X86CPUIDFeature cpuid:8;
     unsigned     vex_class:8;
     X86VEXSpecial vex_special:8;
+    uint16_t     valid_prefix:16;
     bool         is_decode:1;
 };
 
-- 
2.37.3