From: Alex Bennée <alex.bennee@linaro.org>
Date: Wed, 9 Feb 2022 11:21:42 +0000 (+0000)
Subject: tcg/optimize: only read val after const check
X-Git-Tag: v7.0.0-rc0~26^2~20
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=9becc36f0285da206150bc4f0c774f3298aaa439;p=thirdparty%2Fqemu.git

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 e5730009510..06213fd4344 100644
--- 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;