More simple math opts (#1414)

* optimize more simple math operations: mul of 0, or of 0, and of 0, mul of 1, mul of a power of 2, urem of a power of 2

* fix asm2wasm callImport parsing: the optimizer may get rid of the added offset to a function table

* update js builds

2 files changed, 10 insertions, 5 deletions

diff --git a/src/support/bits.h b/src/support/bits.h
index 1fba58bf1..73d71e804 100644
--- a/src/support/bits.h
+++ b/src/support/bits.h
@@ -29,6 +29,9 @@
  *
  * We instead use portable and reasonably-fast implementations, while
  * avoiding implementations with large lookup tables.
+ *
+ * TODO: The convention here should be changed PopCount => popCount,
+ *       initial lowercase, to match the rest of the codebase.
  */
 
 namespace wasm {
@@ -65,6 +68,10 @@ template <typename T>
 int CountLeadingZeroes(T v) {
   return CountLeadingZeroes(typename std::make_unsigned<T>::type(v));
 }
+template <typename T>
+bool IsPowerOf2(T v) {
+  return v != 0 && PopCount(v) == 1;
+}
 
 template <typename T, typename U>
 inline static T RotateLeft(T val, U count) {
diff --git a/src/support/utilities.h b/src/support/utilities.h
index 66e7ed797..a2fff7f0a 100644
--- a/src/support/utilities.h
+++ b/src/support/utilities.h
@@ -26,6 +26,8 @@
 #include <iostream>
 #include <type_traits>
 
+#include "support/bits.h"
+
 namespace wasm {
 
 // Type punning needs to be done through this function to avoid undefined
@@ -41,12 +43,8 @@ inline Destination bit_cast(const Source& source) {
   return destination;
 }
 
-inline bool isPowerOf2(uint32_t v) {
-  return v && !(v & (v - 1));
-}
-
 inline size_t alignAddr(size_t address, size_t alignment) {
-  assert(alignment && isPowerOf2((uint32_t)alignment) &&
+  assert(alignment && IsPowerOf2((uint32_t)alignment) &&
          "Alignment is not a power of two!");
 
   assert(address + alignment - 1 >= address);