When double-clicking a node, display the assembly code for the native symbol with the highest sample count.

Author: mstange

src/profile-logic/bottom-box.ts

@@ -16,6 +16,7 @@ import {
   getCallNodeFramePerStack,
   getNativeSymbolInfo,
   getNativeSymbolsForCallNode,
+  getNativeSymbolTimingsForCallNode,
 } from './profile-data';
 import { mapGetKeyWithMaxValue } from 'firefox-profiler/utils';
 import { getLineTimingsForCallNode } from './line-timings';
@@ -56,18 +57,34 @@ export function getBottomBoxInfoForCallNode(
     callNodeInfo,
     stackTable
   );
+
+  // If we have at least one native symbol to show assembly for, pick
+  // the one with the highest total.
   const nativeSymbolsForCallNode = getNativeSymbolsForCallNode(
     callNodeFramePerStack,
     frameTable
   );
+  let initialNativeSymbol = null;
+  const nativeSymbolTimings = getNativeSymbolTimingsForCallNode(
+    samples,
+    callNodeFramePerStack,
+    frameTable
+  );
+  const hottestNativeSymbol = mapGetKeyWithMaxValue(nativeSymbolTimings);
+  if (hottestNativeSymbol !== undefined) {
+    nativeSymbolsForCallNode.add(hottestNativeSymbol);
+    initialNativeSymbol = hottestNativeSymbol;
+  }
+  const nativeSymbolsForCallNodeArr = [...nativeSymbolsForCallNode];
+  nativeSymbolsForCallNodeArr.sort((a, b) => a - b);
+  if (
+    nativeSymbolsForCallNodeArr.length !== 0 &&
+    initialNativeSymbol === null
+  ) {
+    initialNativeSymbol = nativeSymbolsForCallNodeArr[0];
+  }
 
-  // If we have at least one native symbol to show assembly for, pick
-  // the first one arbitrarily.
-  // TODO: If the we have more than one native symbol, pick the one
-  // with the highest total sample count.
-  const initialNativeSymbol = nativeSymbolsForCallNode.length !== 0 ? 0 : null;
-
-  const nativeSymbolInfosForCallNode = nativeSymbolsForCallNode.map(
+  const nativeSymbolInfosForCallNode = nativeSymbolsForCallNodeArr.map(
     (nativeSymbolIndex) =>
       getNativeSymbolInfo(
         nativeSymbolIndex,
@@ -91,17 +108,18 @@ export function getBottomBoxInfoForCallNode(
     samples,
     callNodeFramePerStack,
     frameTable,
-    initialNativeSymbol !== null
-      ? nativeSymbolsForCallNode[initialNativeSymbol]
-      : null
+    initialNativeSymbol
   );
   const hottestInstructionAddress = mapGetKeyWithMaxValue(addressTimings);
 
   return {
     libIndex,
     sourceIndex,
     nativeSymbols: nativeSymbolInfosForCallNode,
-    initialNativeSymbol,
+    initialNativeSymbol:
+      initialNativeSymbol !== null
+        ? nativeSymbolsForCallNodeArr.indexOf(initialNativeSymbol)
+        : null,
     scrollToLineNumber: hottestLine,
     scrollToInstructionAddress: hottestInstructionAddress,
   };

src/profile-logic/profile-data.ts

@@ -4045,8 +4045,8 @@ export function calculateFunctionSizeLowerBound(
 export function getNativeSymbolsForCallNode(
   callNodeFramePerStack: Int32Array,
   frameTable: FrameTable
-): IndexIntoNativeSymbolTable[] {
-  const set: Set<IndexIntoNativeSymbolTable> = new Set();
+): Set<IndexIntoNativeSymbolTable> {
+  const set = new Set<IndexIntoNativeSymbolTable>();
   for (
     let stackIndex = 0;
     stackIndex < callNodeFramePerStack.length;
@@ -4060,7 +4060,39 @@ export function getNativeSymbolsForCallNode(
       }
     }
   }
-  return [...set];
+  return set;
+}
+
+export function getNativeSymbolTimingsForCallNode(
+  samples: SamplesLikeTable,
+  callNodeFramePerStack: Int32Array,
+  frameTable: FrameTable
+): Map<IndexIntoNativeSymbolTable, number> {
+  const totalPerNativeSymbol = new Map<Address, number>();
+  for (let sampleIndex = 0; sampleIndex < samples.length; sampleIndex++) {
+    const stack = samples.stack[sampleIndex];
+    if (stack === null) {
+      continue;
+    }
+    const callNodeFrame = callNodeFramePerStack[stack];
+    if (callNodeFrame === -1) {
+      // This sample does not contribute to the call node's total. Ignore.
+      continue;
+    }
+
+    const sampleWeight =
+      samples.weight !== null ? samples.weight[sampleIndex] : 1;
+
+    const nativeSymbol = frameTable.nativeSymbol[callNodeFrame];
+    if (nativeSymbol !== null) {
+      totalPerNativeSymbol.set(
+        nativeSymbol,
+        (totalPerNativeSymbol.get(nativeSymbol) ?? 0) + sampleWeight
+      );
+    }
+  }
+
+  return totalPerNativeSymbol;
 }
 
 /**

src/test/unit/profile-data.test.ts

@@ -1481,7 +1481,7 @@ describe('getNativeSymbolsForCallNode', function () {
     );
     expect(
       getNativeSymbolsForCallNode(callNodeFramePerStackAB, thread.frameTable)
-    ).toEqual([symB]);
+    ).toEqual(new Set([symB]));
 
     const callNodeFramePerStackABC = getCallNodeFramePerStack(
       ensureExists(abc),
@@ -1490,7 +1490,7 @@ describe('getNativeSymbolsForCallNode', function () {
     );
     expect(
       getNativeSymbolsForCallNode(callNodeFramePerStackABC, thread.frameTable)
-    ).toEqual([symB]);
+    ).toEqual(new Set([symB]));
   });
 
   it('finds multiple symbols', function () {
@@ -1531,9 +1531,7 @@ describe('getNativeSymbolsForCallNode', function () {
       thread.stackTable
     );
     expect(
-      new Set(
-        getNativeSymbolsForCallNode(callNodeFramePerStackC, thread.frameTable)
-      )
+      getNativeSymbolsForCallNode(callNodeFramePerStackC, thread.frameTable)
     ).toEqual(new Set([symB, symD]));
   });
 });