bound check hints concrete (f redesign)

crypto/blake256/hasher.go

@@ -367,7 +367,6 @@ func (h *hasher) saveState(target []byte, prefix uint32) []byte {
 		h.putSavedState(state[:], prefix)
 		return append(target, state[:]...)
 	}
-	_ = target[:len(target)+SavedStateSize] // Bounds check hint to compiler.
 	h.putSavedState(target[len(target):len(target)+SavedStateSize], prefix)
 	return target[:len(target)+SavedStateSize]
 }

crypto/blake256/internal/compress/blocks_generic.go

@@ -107,11 +107,14 @@ func blocksGeneric(state *State, msg []byte, counter uint64) {
 	// Ideally these hints wouldn't be necessary, but they do make quite a big
 	// difference in avoiding a bunch of additional bounds checks as determined
 	// by both reviewing the resulting compiled asm as well as benchmarks.
-	h := state.CV[:8]       // Bounds check hint to compiler.
-	s := state.S[:4]        // Bounds check hint to compiler.
-	m := state.scratch[:16] // Bounds check hint to compiler.
+	h := &state.CV
+	s := &state.S
+	m := &state.scratch
+	_ = h[7]  // Bounds check hints to compiler.
+	_ = s[3]  // Bounds check hint to compiler.
+	_ = m[15] // Bounds check hint to compiler.
 	for numBlocks := len(msg) >> blockSizeLog2; numBlocks > 0; numBlocks-- {
-		_ = msg[:64] // Bounds check hint to compiler.
+		_ = msg[63] // Bounds check hint to compiler.
 
 		// Convert the provided message of at least 64 bytes to an array of 16
 		// 32-bit unsigned big-endian words.