SafeMul: avoid UB on signed overflow

Bug: http://b/395138850
Test: atest art-run-test-530-checker-loops4
Change-Id: Id7fb236cc4cbc7982de1a8e79f94814f9daf2bd1

1 files changed, 3 insertions, 2 deletions

diff --git a/compiler/optimizing/induction_var_range.cc b/compiler/optimizing/induction_var_range.cc
index 2f5a22ec0e..1fa2724641 100644
--- a/compiler/optimizing/induction_var_range.cc
+++ b/compiler/optimizing/induction_var_range.cc
@@ -48,10 +48,11 @@ static bool IsSafeDiv(int32_t c1, int32_t c2) {
 
 /** Computes a * b for a,b > 0 (at least until first overflow happens). */
 static int64_t SafeMul(int64_t a, int64_t b, /*out*/ bool* overflow) {
-  if (a > 0 && b > 0 && a > (std::numeric_limits<int64_t>::max() / b)) {
+  int64_t result;
+  if (__builtin_mul_overflow(a, b, &result)) {
     *overflow = true;
   }
-  return a * b;
+  return result;
 }
 
 /** Returns b^e for b,e > 0. Sets overflow if arithmetic wrap-around occurred. */