Fix Log2Int type construction

tiehuis · tiehuis · commit 212449bc2310 · 2018-06-06T22:41:55.000+12:00
The following case for example, would previously fail:

    const a = u24(1) &lt;&lt; Log2Int(u24)(22);
diff --git a/std/math/index.zig b/std/math/index.zig
@@ -306,7 +306,14 @@ test "math.rotl" {
 }
 
 pub fn Log2Int(comptime T: type) type {
-    return @IntType(false, log2(T.bit_count));
+    // comptime ceil log2
+    comptime var count: usize = 0;
+    comptime var s = T.bit_count - 1;
+    inline while (s != 0) : (s >>= 1) {
+        count += 1;
+    }
+
+    return @IntType(false, count);
 }
 
 test "math overflow functions" {

Original file line number	Diff line number	Diff line change
`@@ -306,7 +306,14 @@ test "math.rotl" {`
`306`	`306`	`}`
`307`	`307`
`308`	`308`	`pub fn Log2Int(comptime T: type) type {`
`309`		`- return @IntType(false, log2(T.bit_count));`
	`309`	`+ // comptime ceil log2`
	`310`	`+ comptime var count: usize = 0;`
	`311`	`+ comptime var s = T.bit_count - 1;`
	`312`	`+ inline while (s != 0) : (s >>= 1) {`
	`313`	`+ count += 1;`
	`314`	`+ }`
	`315`	`+`
	`316`	`+ return @IntType(false, count);`
`310`	`317`	`}`
`311`	`318`
`312`	`319`	`test "math overflow functions" {`