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C++: Remove one nomagic and explain the other

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This commit is contained in:
Jonas Jensen
2019-08-26 21:48:18 +02:00
parent 2332dada1a
commit 4cae5917cb
2 changed files with 8 additions and 2 deletions
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5
cpp/ql/src/semmle/code/cpp/controlflow/SubBasicBlocks.qll
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@@ -101,7 +101,6 @@ class SubBasicBlock extends ControlFlowNodeBase {
* start from 0, and the node at index 0 always exists and compares equal
* to `this`.
*/
pragma[nomagic]
ControlFlowNode getNode(int index) {
exists(BasicBlock bb |
exists(int outerIndex |
@@ -115,6 +114,10 @@ class SubBasicBlock extends ControlFlowNodeBase {
* Gets the index of the node in this `SubBasicBlock` that has `indexInBB` in
* `bb`, where `bb` is equal to `getBasicBlock()`.
*/
// This predicate is factored out of `getNode` to ensure a good join order.
// It's sensitive to bad magic, so it has `pragma[nomagic]` on it. For
// example, it can get very slow if `getNode` is pragma[nomagic], which could
// mean it might get very slow if `getNode` is used in the wrong context.
pragma[nomagic]
private int outerToInnerIndex(BasicBlock bb, int indexInBB) {
indexInBB = result + this.getIndexInBasicBlock(bb) and

5
cpp/ql/src/semmle/code/cpp/dataflow/internal/SubBasicBlocks.qll
View File

@@ -101,7 +101,6 @@ class SubBasicBlock extends ControlFlowNodeBase {
* start from 0, and the node at index 0 always exists and compares equal
* to `this`.
*/
pragma[nomagic]
ControlFlowNode getNode(int index) {
exists(BasicBlock bb |
exists(int outerIndex |
@@ -115,6 +114,10 @@ class SubBasicBlock extends ControlFlowNodeBase {
* Gets the index of the node in this `SubBasicBlock` that has `indexInBB` in
* `bb`, where `bb` is equal to `getBasicBlock()`.
*/
// This predicate is factored out of `getNode` to ensure a good join order.
// It's sensitive to bad magic, so it has `pragma[nomagic]` on it. For
// example, it can get very slow if `getNode` is pragma[nomagic], which could
// mean it might get very slow if `getNode` is used in the wrong context.
pragma[nomagic]
private int outerToInnerIndex(BasicBlock bb, int indexInBB) {
indexInBB = result + this.getIndexInBasicBlock(bb) and