Half of day 38 complete.

handmade_intrinsics.h

@@ -5,6 +5,7 @@
          math.h. */
 
 #include <math.h>
+#include <string.h> // memset
 
 S32 RoundF32toS32(F32 Real32)
 {
@@ -36,5 +37,38 @@ F32 ATan2(F32 Y, F32 X)
     return Result;
 }
 
+typedef struct bit_scan_result {
+    B32 Found;
+    U32 Index;
+} bit_scan_result;
+
+static bit_scan_result FindLeastSignificantSetBit(U32 Value)
+{
+    bit_scan_result Result;
+    memset(&Result, 0, sizeof(Result));
+
+#if COMPILER_MSVC
+    Result.Found = _BitScanForward(&Result.Index, Value); // TODO: I have not tested this.
+#elif COMPILER_CLANG
+    Result.Index = __builtin_ffsll(Value); // NOTE: It is a GCC function, but is supported by clang compiler.
+                                           // https://gcc.gnu.org/onlinedocs/gcc/Bit-Operation-Builtins.html
+    if(Result.Index) {
+        Result.Found = TRUE;
+        if(Result.Index > 0)
+            Result.Index--;
+    }
+#else
+    for(U32 Test = 0; Test < 32; Test++) {
+        if(Value & (1 << Test)) {
+            Result.Index = Test;
+            Result.Found = TRUE;
+            break;
+        }
+    }
+#endif
+
+    return Result;
+}
+
 #endif