abi, wit: align without division

bytecodealliance · Oct 19, 2023 · 696040f · 696040f
1 parent e5d4ed8
commit 696040f
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Showing 2 changed files with 2 additions and 6 deletions.
diff --git a/abi/realloc.go b/abi/realloc.go
@@ -23,9 +23,7 @@ func realloc(ptr unsafe.Pointer, size, align, newsize uintptr) unsafe.Pointer {
 // offset returns the delta between the aligned value of ptr and ptr
 // so it can be passed to unsafe.Add. The return value is guaranteed to be >= 0.
 func offset(ptr, align uintptr) uintptr {
-	// (dividend + divisor - 1) / divisor
-	// http://www.cs.nott.ac.uk/~rcb/G51MPC/slides/NumberLogic.pdf
-	newptr := ((ptr + align - 1) / align) * align
+	newptr := (ptr + align - 1) &^ (align - 1)
 	return newptr - ptr
 }
 

diff --git a/wit/abi.go b/wit/abi.go
@@ -2,9 +2,7 @@ package wit
 
 // Align aligns ptr with alignment align.
 func Align(ptr, align uintptr) uintptr {
-	// (dividend + divisor - 1) / divisor
-	// http://www.cs.nott.ac.uk/~rcb/G51MPC/slides/NumberLogic.pdf
-	return ((ptr + align - 1) / align) * align
+	return (ptr + align - 1) &^ (align - 1)
 }
 
 // Discriminant returns the smallest WIT integer type that can represent 0...n.