[PATCH v2 26/42] i386: Utility function for 128 bit AVX

[Paul Brook]

VEX encoded instructions that write to a (128 bit) xmm register clear the
rest (upper half) of the corresonding (256 bit) ymm register.
When legacy SSE encodings are used the rest of the ymm register is left
unchanged.

Add a utility fuction so that we don't have to keep duplicating this logic.

Signed-off-by: Paul Brook <paul@nowt.org>
---
 target/i386/tcg/translate.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c
index d148a2319d..278ed8ed1c 100644
--- a/target/i386/tcg/translate.c
+++ b/target/i386/tcg/translate.c
@@ -2780,6 +2780,18 @@ static inline void gen_op_movq_env_0(DisasContext *s, 
int d_offset)
 
 #define ZMM_OFFSET(reg) offsetof(CPUX86State, xmm_regs[reg])
 
+/*
+ * Clear the top half of the ymm register after a VEX.128 instruction
+ * This could be optimized by tracking this in env->hflags
+ */
+static void gen_clear_ymmh(DisasContext *s, int reg)
+{
+    if (s->prefix & PREFIX_VEX) {
+        gen_op_movq_env_0(s, offsetof(CPUX86State, xmm_regs[reg].ZMM_Q(2)));
+        gen_op_movq_env_0(s, offsetof(CPUX86State, xmm_regs[reg].ZMM_Q(3)));
+    }
+}
+
 typedef void (*SSEFunc_i_ep)(TCGv_i32 val, TCGv_ptr env, TCGv_ptr reg);
 typedef void (*SSEFunc_l_ep)(TCGv_i64 val, TCGv_ptr env, TCGv_ptr reg);
 typedef void (*SSEFunc_0_epi)(TCGv_ptr env, TCGv_ptr reg, TCGv_i32 val);
-- 
2.36.0