Add fallback to funcTable.lineNumber when computing line timings (#5644)

When computing line timings for source view, we now fall back to using
funcTable.lineNumber (the function's start line) when frameTable.line
(the frame's execution line) is null. This is particularly useful for
JS JIT'ed functions where frame line information might be missing.

Author: canova

src/profile-logic/line-timings.ts

@@ -82,6 +82,10 @@ export function getStackLineInfo(
 
     if (sourceIndexOfThisStack === sourceViewSourceIndex) {
       selfLine = frameTable.line[frame];
+      // Fallback to func line info if frame line info is not available
+      if (selfLine === null) {
+        selfLine = funcTable.lineNumber[func];
+      }
       if (selfLine !== null) {
         // Add this stack's line to this stack's totalLines. The rest of this stack's
         // totalLines is the same as for the parent stack.
@@ -120,6 +124,7 @@ export function getStackLineInfo(
 export function getStackLineInfoForCallNode(
   stackTable: StackTable,
   frameTable: FrameTable,
+  funcTable: FuncTable,
   callNodeIndex: IndexIntoCallNodeTable,
   callNodeInfo: CallNodeInfo
 ): StackLineInfo {
@@ -128,12 +133,14 @@ export function getStackLineInfoForCallNode(
     ? getStackLineInfoForCallNodeInverted(
         stackTable,
         frameTable,
+        funcTable,
         callNodeIndex,
         callNodeInfoInverted
       )
     : getStackLineInfoForCallNodeNonInverted(
         stackTable,
         frameTable,
+        funcTable,
         callNodeIndex,
         callNodeInfo
       );
@@ -205,6 +212,7 @@ export function getStackLineInfoForCallNode(
 export function getStackLineInfoForCallNodeNonInverted(
   stackTable: StackTable,
   frameTable: FrameTable,
+  funcTable: FuncTable,
   callNodeIndex: IndexIntoCallNodeTable,
   callNodeInfo: CallNodeInfo
 ): StackLineInfo {
@@ -229,6 +237,11 @@ export function getStackLineInfoForCallNodeNonInverted(
       // the same as the given call node's func and file.
       const frame = stackTable.frame[stackIndex];
       selfLine = frameTable.line[frame];
+      // Fallback to func line info if frame line info is not available
+      if (selfLine === null) {
+        const func = frameTable.func[frame];
+        selfLine = funcTable.lineNumber[func];
+      }
       if (selfLine !== null) {
         totalLines = new Set([selfLine]);
       }
@@ -280,6 +293,7 @@ export function getStackLineInfoForCallNodeNonInverted(
 export function getStackLineInfoForCallNodeInverted(
   stackTable: StackTable,
   frameTable: FrameTable,
+  funcTable: FuncTable,
   callNodeIndex: IndexIntoCallNodeTable,
   callNodeInfo: CallNodeInfoInverted
 ): StackLineInfo {
@@ -318,7 +332,12 @@ export function getStackLineInfoForCallNodeInverted(
       // This stack contributes to the call node's total time.
       // We don't need to check the stack's func or file because it'll be
       // the same as the given call node's func and file.
-      const line = frameTable.line[frameForCallNode];
+      let line = frameTable.line[frameForCallNode];
+      // Fallback to func line info if frame line info is not available
+      if (line === null) {
+        const func = frameTable.func[frameForCallNode];
+        line = funcTable.lineNumber[func];
+      }
       if (line !== null) {
         totalLines = new Set([line]);
         if (callNodeIsRootOfInvertedTree) {

src/selectors/per-thread/index.ts

@@ -294,6 +294,7 @@ export const selectedNodeSelectors: NodeSelectors = (() => {
         return getStackLineInfoForCallNode(
           stackTable,
           frameTable,
+          funcTable,
           selectedCallNodeIndex,
           callNodeInfo
         );

src/test/unit/line-timings.test.ts

@@ -112,6 +112,40 @@ describe('getLineTimings for getStackLineInfo', function () {
     expect(lineTimingsTwo.selfLineHits.get(40)).toBe(1);
     expect(lineTimingsTwo.selfLineHits.size).toBe(2); // no other hits
   });
+
+  it('falls back to funcTable.lineNumber when frameTable.line is null', function () {
+    // Create a profile with frames that have null line numbers
+    const { derivedThreads } = getProfileFromTextSamples(`
+      A[file:file.js][line:20]
+      B[file:file.js][line:30]
+    `);
+    const [thread] = derivedThreads;
+    const { stackTable, frameTable, funcTable, samples, stringTable } = thread;
+
+    // Manually set frameTable.line to null for the leaf frame
+    // to simulate a case where frame line info is missing
+    const leafFrame = stackTable.frame[stackTable.length - 1];
+    frameTable.line[leafFrame] = null;
+
+    // Set funcTable.lineNumber to a value for the func of that frame
+    const func = frameTable.func[leafFrame];
+    funcTable.lineNumber[func] = 35;
+
+    const fileStringIndex = stringTable.indexForString('file.js');
+    const fileSourceIndex = thread.sources.filename.indexOf(fileStringIndex);
+    const stackLineInfo = getStackLineInfo(
+      stackTable,
+      frameTable,
+      funcTable,
+      fileSourceIndex
+    );
+    const lineTimings = getLineTimings(stackLineInfo, samples);
+
+    // The fallback should use funcTable.lineNumber[func] = 35
+    expect(lineTimings.selfLineHits.get(35)).toBe(1);
+    expect(lineTimings.totalLineHits.get(20)).toBe(1);
+    expect(lineTimings.totalLineHits.get(35)).toBe(1);
+  });
 });
 
 describe('getLineTimings for getStackLineInfoForCallNode', function () {
@@ -141,6 +175,7 @@ describe('getLineTimings for getStackLineInfoForCallNode', function () {
     const stackLineInfo = getStackLineInfoForCallNode(
       stackTable,
       frameTable,
+      funcTable,
       callNodeIndex,
       callNodeInfo
     );
@@ -268,4 +303,33 @@ describe('getLineTimings for getStackLineInfoForCallNode', function () {
     expect(lineTimingsDBA.totalLineHits.size).toBe(1); // no other hits
     expect(lineTimingsDC.selfLineHits.size).toBe(0); // no self line hits
   });
+
+  it('falls back to funcTable.lineNumber when frameTable.line is null', function () {
+    const { derivedThreads, funcNamesDictPerThread, defaultCategory } =
+      getProfileFromTextSamples(`
+      A[file:file.js][line:20]
+      B[file:file.js][line:30]
+    `);
+
+    const [{ A, B }] = funcNamesDictPerThread;
+    const [thread] = derivedThreads;
+    const { stackTable, frameTable, funcTable } = thread;
+
+    // Manually set frameTable.line to null for the leaf frame
+    // to simulate a case where frame line info is missing
+    const leafFrame = stackTable.frame[stackTable.length - 1];
+    frameTable.line[leafFrame] = null;
+
+    // Set funcTable.lineNumber to a value for the func of that frame
+    const func = frameTable.func[leafFrame];
+    funcTable.lineNumber[func] = 35;
+
+    // Compute the line timings for the child call node.
+    // The fallback should use funcTable.lineNumber[func] = 35
+    const lineTimingsChild = getTimings(thread, [A, B], defaultCategory, false);
+    expect(lineTimingsChild.totalLineHits.get(35)).toBe(1);
+    expect(lineTimingsChild.totalLineHits.size).toBe(1); // no other hits
+    expect(lineTimingsChild.selfLineHits.get(35)).toBe(1);
+    expect(lineTimingsChild.selfLineHits.size).toBe(1); // no other hits
+  });
 });