add Log2 and Pow2 support methods

kripken · kripken · commit 3245c24d1fd5 · 2016-03-16T17:46:46.000-07:00
diff --git a/src/compiler-support.h b/src/compiler-support.h
@@ -32,6 +32,7 @@
 #elif defined(_MSC_VER)
 # define WASM_UNREACHABLE() __assume(false)
 #else
+# include <stdlib.h>
 # define WASM_UNREACHABLE() abort()
 #endif
 
diff --git a/src/support/bits.cpp b/src/support/bits.cpp
@@ -15,6 +15,7 @@
  */
 
 #define wasm_support_bits_definitions
+#include "../compiler-support.h"
 #include "support/bits.h"
 
 namespace wasm {
@@ -99,4 +100,28 @@ int CountLeadingZeroes<uint64_t>(uint64_t v) {
                  : 32 + CountLeadingZeroes((uint32_t)v);
 }
 
+uint32_t Log2(uint32_t v) {
+  switch (v) {
+    default: WASM_UNREACHABLE();
+    case 1: return 0;
+    case 2: return 1;
+    case 4: return 2;
+    case 8: return 3;
+    case 16: return 4;
+    case 32: return 5;
+  }
+}
+
+uint32_t Pow2(uint32_t v) {
+  switch (v) {
+    default: WASM_UNREACHABLE();
+    case 0: return 1;
+    case 1: return 2;
+    case 2: return 4;
+    case 3: return 8;
+    case 4: return 16;
+    case 5: return 32;
+  }
+}
+
 } // namespace wasm
diff --git a/src/support/bits.h b/src/support/bits.h
@@ -79,6 +79,8 @@ inline static T RotateRight(T val, T count) {
   return (val >> count) | (val << (-count & mask));
 }
 
+extern uint32_t Log2(uint32_t v);
+extern uint32_t Pow2(uint32_t v);
 
 }  // namespace wasm
 

Original file line number	Diff line number	Diff line change
`@@ -79,6 +79,8 @@ inline static T RotateRight(T val, T count) {`
`79`	`79`	`return (val >> count) \| (val << (-count & mask));`
`80`	`80`	`}`
`81`	`81`
	`82`	`+extern uint32_t Log2(uint32_t v);`
	`83`	`+extern uint32_t Pow2(uint32_t v);`
`82`	`84`
`83`	`85`	`} // namespace wasm`
`84`	`86`