[turbofan] Add support for overflow add/sub to the MachineOperatorReducer.

src/base/bits.h

Index: src/base/bits.h
diff --git a/src/base/bits.h b/src/base/bits.h
index f271df9067d736e8ac512a9d13b15b04840291d3..e6a733a45dbb24ce4c95a30a817b2de2b4ee2354 100644
--- a/src/base/bits.h
+++ b/src/base/bits.h
@@ -6,6 +6,7 @@
 #define V8_BASE_BITS_H_
 
 #include "include/v8stdint.h"
+#include "src/base/macros.h"
 #if V8_CC_MSVC
 #include <intrin.h>
 #endif
@@ -114,6 +115,34 @@ inline uint64_t RotateRight64(uint64_t value, uint64_t shift) {
   return (value >> shift) | (value << (64 - shift));
 }
 
+
+// SignedAddOverflow32(lhs,rhs,val) performs a signed summation of |lhs| and
+// |rhs| and stores the result into the variable pointed to by |val| and
+// returns true if the signed summation resulted in an overflow.
+inline bool SignedAddOverflow32(int32_t lhs, int32_t rhs, int32_t* val) {
+#if V8_HAS_BUILTIN_SADD_OVERFLOW
+  return __builtin_sadd_overflow(lhs, rhs, val);
+#else
+  uint32_t res = static_cast<uint32_t>(lhs) + static_cast<uint32_t>(rhs);
+  *val = bit_cast<int32_t>(res);
+  return ((res ^ lhs) & (res ^ rhs) & (1U << 31)) != 0;
+#endif
+}
+
+
+// SignedSubOverflow32(lhs,rhs,val) performs a signed subtraction of |lhs| and
+// |rhs| and stores the result into the variable pointed to by |val| and
+// returns true if the signed subtraction resulted in an overflow.
+inline bool SignedSubOverflow32(int32_t lhs, int32_t rhs, int32_t* val) {
+#if V8_HAS_BUILTIN_SSUB_OVERFLOW
+  return __builtin_ssub_overflow(lhs, rhs, val);
+#else
+  uint32_t res = static_cast<uint32_t>(lhs) - static_cast<uint32_t>(rhs);
+  *val = bit_cast<int32_t>(res);
+  return ((res ^ lhs) & (res ^ ~rhs) & (1U << 31)) != 0;
+#endif
+}
+
 }  // namespace bits
 }  // namespace base
 }  // namespace v8