tcg/optimize: only read val after const check

valgrind pointed out that arg_info()->val can be undefined which will
be the case if the arguments are not constant. The ordering of the
checks will have ensured we never relied on an undefined value but for
the sake of completeness re-order the code to be clear.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220209112142.3367525-1-alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

diff --git a/tcg/optimize.c b/tcg/optimize.c
index e57300095102c27cfe7889455c5d2ba0d065db97..06213fd4344105ce64bbe4c944968298e13b3409 100644 (file)
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -552,10 +552,10 @@ static bool do_constant_folding_cond_eq(TCGCond c)
 static int do_constant_folding_cond(TCGType type, TCGArg x,
                                     TCGArg y, TCGCond c)
 {
-    uint64_t xv = arg_info(x)->val;
-    uint64_t yv = arg_info(y)->val;
-
     if (arg_is_const(x) && arg_is_const(y)) {
+        uint64_t xv = arg_info(x)->val;
+        uint64_t yv = arg_info(y)->val;
+
         switch (type) {
         case TCG_TYPE_I32:
             return do_constant_folding_cond_32(xv, yv, c);
@@ -567,7 +567,7 @@ static int do_constant_folding_cond(TCGType type, TCGArg x,
         }
     } else if (args_are_copies(x, y)) {
         return do_constant_folding_cond_eq(c);
-    } else if (arg_is_const(y) && yv == 0) {
+    } else if (arg_is_const(y) && arg_info(y)->val == 0) {
         switch (c) {
         case TCG_COND_LTU:
             return 0;