compiler: Known hooks/nonescaping scopes dont count as pruned

There are two cases where it's legit/intended to remove scopes, and we can inline the scope rather than reify a "pruned" scope: * Scopes that contain a single instruction with a hook call. The fact that we create a scope in this case at all is just an artifact of it being simpler to do this and remove the scope later rather than try to avoid creating it in the first place. So for these scopes, we can just inline them. * Scopes that are provably non-escaping. Removing the scope is an optimization, not a case of us having to prune away something that should be there. So again, its fine to inline in this case. I found this from syncing the stack internally and looking at differences in compiled output. The latter case was most common but the first case is just an obvious improvement. ghstack-source-id: 80610ddafad65eb837d0037e2692dd74bc548088 Pull Request resolved: #29820
facebook · Jun 10, 2024 · c8d7276 · c8d7276
1 parent 4fa8fa7
commit c8d7276
Show file tree

Hide file tree

Showing 8 changed files with 162 additions and 55 deletions.
diff --git a/compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/CodegenReactiveFunction.ts b/compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/CodegenReactiveFunction.ts
@@ -331,29 +331,8 @@ class CountMemoBlockVisitor extends ReactiveFunctionVisitor<void> {
     scopeBlock: PrunedReactiveScopeBlock,
     state: void
   ): void {
-    let isHookOnlyMemoBlock = false;
-    if (
-      scopeBlock.instructions.length === 1 &&
-      scopeBlock.instructions[0].kind === "instruction"
-    ) {
-      const instr = scopeBlock.instructions[0]!.instruction;
-      if (
-        instr.value.kind === "MethodCall" ||
-        instr.value.kind === "CallExpression"
-      ) {
-        const callee =
-          instr.value.kind === "MethodCall"
-            ? instr.value.property
-            : instr.value.callee;
-        if (getHookKind(this.env, callee.identifier) != null) {
-          isHookOnlyMemoBlock = true;
-        }
-      }
-    }
-    if (!isHookOnlyMemoBlock) {
-      this.prunedMemoBlocks += 1;
-      this.prunedMemoValues += scopeBlock.scope.declarations.size;
-    }
+    this.prunedMemoBlocks += 1;
+    this.prunedMemoValues += scopeBlock.scope.declarations.size;
     this.traversePrunedScope(scopeBlock, state);
   }
 }

diff --git a/...er/packages/babel-plugin-react-compiler/src/ReactiveScopes/FlattenScopesWithHooksOrUse.ts b/...er/packages/babel-plugin-react-compiler/src/ReactiveScopes/FlattenScopesWithHooksOrUse.ts
@@ -66,6 +66,20 @@ class Transform extends ReactiveFunctionTransform<State> {
     this.visitScope(scope, innerState);
     outerState.hasHook ||= innerState.hasHook;
     if (innerState.hasHook) {
+      if (scope.instructions.length === 1) {
+        /*
+         * This was a scope just for a hook call, which doesn't need memoization.
+         * flatten it away
+         */
+        return {
+          kind: "replace-many",
+          value: scope.instructions,
+        };
+      }
+      /*
+       * else this scope had multiple instructions and produced some other value:
+       * mark it as pruned
+       */
       return {
         kind: "replace",
         value: {

diff --git a/compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/PruneNonEscapingScopes.ts b/compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/PruneNonEscapingScopes.ts
@@ -951,12 +951,8 @@ class PruneScopesTransform extends ReactiveFunctionTransform<
     } else {
       this.prunedScopes.add(scopeBlock.scope.id);
       return {
-        kind: "replace",
-        value: {
-          kind: "pruned-scope",
-          scope: scopeBlock.scope,
-          instructions: scopeBlock.instructions,
-        },
+        kind: "replace-many",
+        value: scopeBlock.instructions,
       };
     }
   }

diff --git a/...react-compiler/src/__tests__/fixtures/compiler/log-pruned-memoization.expect.md b/...react-compiler/src/__tests__/fixtures/compiler/log-pruned-memoization.expect.md
@@ -3,10 +3,17 @@
 
 ```javascript
 // @logger
-import { useState } from "react";
-import { identity, makeObject_Primitives, useHook } from "shared-runtime";
+import { createContext, use, useState } from "react";
+import {
+  Stringify,
+  identity,
+  makeObject_Primitives,
+  useHook,
+} from "shared-runtime";
 
 function Component() {
+  const w = use(Context);
+
   // The scopes for x and x2 are interleaved, so this is one scope with two values
   const x = makeObject_Primitives();
   const x2 = makeObject_Primitives();
@@ -26,11 +33,21 @@ function Component() {
   }
 
   // Overall we expect two pruned scopes (for x+x2, and obj), with 3 pruned scope values.
-  return [x, x2, y, z];
+  return <Stringify items={[w, x, x2, y, z]} />;
+}
+
+const Context = createContext();
+
+function Wrapper() {
+  return (
+    <Context value={42}>
+      <Component />
+    </Context>
+  );
 }
 
 export const FIXTURE_ENTRYPOINT = {
-  fn: Component,
+  fn: Wrapper,
   params: [{}],
 };
 
@@ -40,11 +57,17 @@ export const FIXTURE_ENTRYPOINT = {
 
 ```javascript
 import { c as _c } from "react/compiler-runtime"; // @logger
-import { useState } from "react";
-import { identity, makeObject_Primitives, useHook } from "shared-runtime";
+import { createContext, use, useState } from "react";
+import {
+  Stringify,
+  identity,
+  makeObject_Primitives,
+  useHook,
+} from "shared-runtime";
 
 function Component() {
-  const $ = _c(5);
+  const $ = _c(6);
+  const w = use(Context);
 
   const x = makeObject_Primitives();
   const x2 = makeObject_Primitives();
@@ -65,20 +88,39 @@ function Component() {
     z = $[0];
   }
   let t0;
-  if ($[1] !== x || $[2] !== x2 || $[3] !== y) {
-    t0 = [x, x2, y, z];
-    $[1] = x;
-    $[2] = x2;
-    $[3] = y;
-    $[4] = t0;
+  if ($[1] !== w || $[2] !== x || $[3] !== x2 || $[4] !== y) {
+    t0 = <Stringify items={[w, x, x2, y, z]} />;
+    $[1] = w;
+    $[2] = x;
+    $[3] = x2;
+    $[4] = y;
+    $[5] = t0;
+  } else {
+    t0 = $[5];
+  }
+  return t0;
+}
+
+const Context = createContext();
+
+function Wrapper() {
+  const $ = _c(1);
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = (
+      <Context value={42}>
+        <Component />
+      </Context>
+    );
+    $[0] = t0;
   } else {
-    t0 = $[4];
+    t0 = $[0];
   }
   return t0;
 }
 
 export const FIXTURE_ENTRYPOINT = {
-  fn: Component,
+  fn: Wrapper,
   params: [{}],
 };
 
@@ -87,8 +129,9 @@ export const FIXTURE_ENTRYPOINT = {
 ## Logs
 
 ```
-{"kind":"CompileSuccess","fnLoc":{"start":{"line":5,"column":0,"index":121},"end":{"line":26,"column":1,"index":813},"filename":"log-pruned-memoization.ts"},"fnName":"Component","memoSlots":5,"memoBlocks":2,"memoValues":2,"prunedMemoBlocks":2,"prunedMemoValues":3}
+{"kind":"CompileSuccess","fnLoc":{"start":{"line":10,"column":0,"index":161},"end":{"line":33,"column":1,"index":905},"filename":"log-pruned-memoization.ts"},"fnName":"Component","memoSlots":6,"memoBlocks":2,"memoValues":2,"prunedMemoBlocks":2,"prunedMemoValues":3}
+{"kind":"CompileSuccess","fnLoc":{"start":{"line":37,"column":0,"index":941},"end":{"line":43,"column":1,"index":1039},"filename":"log-pruned-memoization.ts"},"fnName":"Wrapper","memoSlots":1,"memoBlocks":1,"memoValues":1,"prunedMemoBlocks":0,"prunedMemoValues":0}
 ```
       
 ### Eval output
-(kind: ok) [{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},[{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true}]]
+(kind: ok) <div>{"items":[42,{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},[{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true},{"a":0,"b":"value1","c":true}]]}</div>
diff --git a/...ges/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/log-pruned-memoization.js b/...ges/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/log-pruned-memoization.js
@@ -1,8 +1,15 @@
 // @logger
-import { useState } from "react";
-import { identity, makeObject_Primitives, useHook } from "shared-runtime";
+import { createContext, use, useState } from "react";
+import {
+  Stringify,
+  identity,
+  makeObject_Primitives,
+  useHook,
+} from "shared-runtime";
 
 function Component() {
+  const w = use(Context);
+
   // The scopes for x and x2 are interleaved, so this is one scope with two values
   const x = makeObject_Primitives();
   const x2 = makeObject_Primitives();
@@ -22,10 +29,20 @@ function Component() {
   }
 
   // Overall we expect two pruned scopes (for x+x2, and obj), with 3 pruned scope values.
-  return [x, x2, y, z];
+  return <Stringify items={[w, x, x2, y, z]} />;
+}
+
+const Context = createContext();
+
+function Wrapper() {
+  return (
+    <Context value={42}>
+      <Component />
+    </Context>
+  );
 }
 
 export const FIXTURE_ENTRYPOINT = {
-  fn: Component,
+  fn: Wrapper,
   params: [{}],
 };
diff --git a/...ler/nonreactive-noescaping-dependency-can-inline-into-consuming-scope.expect.md b/...ler/nonreactive-noescaping-dependency-can-inline-into-consuming-scope.expect.md
@@ -0,0 +1,46 @@
+
+## Input
+
+```javascript
+// @flow
+function Component() {
+  return (
+    <div
+      className={stylex(
+        // this value is a) in its own scope, b) non-reactive, and c) non-escaping
+        // its scope gets pruned bc it's non-escaping, but this doesn't mean we need to
+        // create a temporary for it
+        flags.feature("feature-name") ? styles.featureNameStyle : null
+      )}
+    ></div>
+  );
+}
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime";
+function Component() {
+  const $ = _c(1);
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = (
+      <div
+        className={stylex(
+          flags.feature("feature-name") ? styles.featureNameStyle : null,
+        )}
+      />
+    );
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+```
+      
+### Eval output
+(kind: exception) Fixture not implemented
diff --git a/...__/fixtures/compiler/nonreactive-noescaping-dependency-can-inline-into-consuming-scope.js b/...__/fixtures/compiler/nonreactive-noescaping-dependency-can-inline-into-consuming-scope.js
@@ -0,0 +1,13 @@
+// @flow
+function Component() {
+  return (
+    <div
+      className={stylex(
+        // this value is a) in its own scope, b) non-reactive, and c) non-escaping
+        // its scope gets pruned bc it's non-escaping, but this doesn't mean we need to
+        // create a temporary for it
+        flags.feature("feature-name") ? styles.featureNameStyle : null
+      )}
+    ></div>
+  );
+}
diff --git a/...mpiler/reactive-control-dependency-from-interleaved-reactivity-for-of.expect.md b/...mpiler/reactive-control-dependency-from-interleaved-reactivity-for-of.expect.md
@@ -39,7 +39,7 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 import { c as _c } from "react/compiler-runtime";
 function Component(props) {
-  const $ = _c(2);
+  const $ = _c(1);
 
   const a = [];
   const b = [];
@@ -53,12 +53,11 @@ function Component(props) {
     x = 1;
   }
   let t0;
-  if ($[0] !== x) {
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
     t0 = [x];
-    $[0] = x;
-    $[1] = t0;
+    $[0] = t0;
   } else {
-    t0 = $[1];
+    t0 = $[0];
   }
   return t0;
 }