tcg/optimize: optimize "op r, a, a => movi r, 0"
Now that it's possible to detect copies, we can optimize the case
the "op r, a, a => movi r, 0". This helps in the computation of
overflow flags when one of the two args is 0.
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
diff --git a/tcg/optimize.c b/tcg/optimize.c
index b9a7da9..ceea644 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -540,6 +540,22 @@
break;
}
+ /* Simplify expression for "op r, a, a => movi r, 0" cases */
+ switch (op) {
+ CASE_OP_32_64(sub):
+ CASE_OP_32_64(xor):
+ if (temps_are_copies(args[1], args[2])) {
+ gen_opc_buf[op_index] = op_to_movi(op);
+ tcg_opt_gen_movi(gen_args, args[0], 0);
+ gen_args += 2;
+ args += 3;
+ continue;
+ }
+ break;
+ default:
+ break;
+ }
+
/* Propagate constants through copy operations and do constant
folding. Constants will be substituted to arguments by register
allocator where needed and possible. Also detect copies. */