C++: Unroll recursion in inStaticInitializer

jbj · jbj · commit bf43475ff7ca · 2020-03-10T17:07:44.000+01:00
This gets rid of some slow recursive magic.

On Wireshark, this improves the timing of the involved predicates from

    m#Variable::runtimeExprInStaticInitializer#b ..................... 3.1s (executed 86 times)
    Variable::runtimeExprInStaticInitializer#b#antijoin_rhs .......... 1.6s
    Variable::runtimeExprInStaticInitializer#b ....................... 985ms (executed 6 times)
    Variable::runtimeExprInStaticInitializer#b#loop_invariant_prefix . 845ms
    #Expr::Expr::getParent_dispred#fbPlus ............................ 3.6s (executed 86 times)
    #Expr::Expr::getParent_dispred#fbPlus_10#join_rhs ................ 988ms

to

    Variable::runtimeExprInStaticInitializer#f#antijoin_rhs . 1.8s
    Variable::runtimeExprInStaticInitializer#f .............. 1.1s (executed 6 times)
    Variable::inStaticInitializer#f ......................... 3.2s (executed 86 times)
diff --git a/cpp/ql/src/semmle/code/cpp/Variable.qll b/cpp/ql/src/semmle/code/cpp/Variable.qll
@@ -404,7 +404,9 @@ private predicate runtimeExprInStaticInitializer(Expr e) {
 
 /** Holds if `e` is part of the initializer of a `StaticStorageDurationVariable`. */
 private predicate inStaticInitializer(Expr e) {
-  exists(StaticStorageDurationVariable var | e.getParent+() = var.getInitializer())
+  exists(StaticStorageDurationVariable var | e = var.getInitializer().getExpr())
+  or
+  inStaticInitializer(e.getParent())
 }
 
 /**

Original file line number	Diff line number	Diff line change
`@@ -404,7 +404,9 @@ private predicate runtimeExprInStaticInitializer(Expr e) {`
`404`	`404`
`405`	`405`	/** Holds if `e` is part of the initializer of a `StaticStorageDurationVariable`. */
`406`	`406`	`private predicate inStaticInitializer(Expr e) {`
`407`		`- exists(StaticStorageDurationVariable var \| e.getParent+() = var.getInitializer())`
	`407`	`+ exists(StaticStorageDurationVariable var \| e = var.getInitializer().getExpr())`
	`408`	`+ or`
	`409`	`+ inStaticInitializer(e.getParent())`
`408`	`410`	`}`
`409`	`411`
`410`	`412`	`/**`