[PATCH 4/4] tcg/optimize: optimize TSTNE using smask and zmask

[Paolo Bonzini]

Generalize the existing optimization of "TSTNE x,sign" and "TSTNE x,-1".

This can be useful in some cases when the i386 frontend creates opcodes
that test against 0xff or 0x80.

Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
 tcg/optimize.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/tcg/optimize.c b/tcg/optimize.c
index 752cc5c56b6..ab976a5bbe7 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -793,6 +793,7 @@ static int do_constant_folding_cond1(OptContext *ctx, TCGOp 
*op, TCGArg dest,
                                      TCGArg *p1, TCGArg *p2, TCGArg *pcond)
 {
     TCGCond cond;
+    TempOptInfo *i1;
     bool swap;
     int r;
 
@@ -810,19 +811,21 @@ static int do_constant_folding_cond1(OptContext *ctx, 
TCGOp *op, TCGArg dest,
         return -1;
     }
 
+    i1 = arg_info(*p1);
+
     /*
      * TSTNE x,x -> NE x,0
-     * TSTNE x,-1 -> NE x,0
+     * TSTNE x,i -> NE x,0 if i includes all nonzero bits of x
      */
-    if (args_are_copies(*p1, *p2) || arg_is_const_val(*p2, -1)) {
+    if (args_are_copies(*p1, *p2) ||
+        (arg_is_const(*p2) && (i1->z_mask & ~arg_info(*p2)->val) == 0)) {
         *p2 = arg_new_constant(ctx, 0);
         *pcond = tcg_tst_eqne_cond(cond);
         return -1;
     }
 
-    /* TSTNE x,sign -> LT x,0 */
-    if (arg_is_const_val(*p2, (ctx->type == TCG_TYPE_I32
-                               ? INT32_MIN : INT64_MIN))) {
+    /* TSTNE x,i -> LT x,0 if i only includes sign bit copies */
+    if (arg_is_const(*p2) && (arg_info(*p2)->val & ~i1->s_mask) == 0) {
         *p2 = arg_new_constant(ctx, 0);
         *pcond = tcg_tst_ltge_cond(cond);
         return -1;
-- 
2.43.2