[compiler] Instruction reordering

Adds a pass just after DCE to reorder safely reorderable instructions (jsx, primitives, globals) closer to where they are used, to allow other optimization passes to be more effective. Notably, the reordering allows scope merging to be more effective, since that pass relies on two scopes not having intervening instructions — in many cases we can now reorder such instructions out of the way and unlock merging, as demonstrated in the changed fixtures.

The algorithm itself is described in the docblock.

note: This is a cleaned up version of #29579 that is ready for review.

ghstack-source-id: c54a806cad7aefba4ac1876c9fd9b25f9177e95a
Pull Request resolved: #29863

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Pipeline.ts

@@ -41,6 +41,7 @@ import {
   deadCodeElimination,
   pruneMaybeThrows,
 } from "../Optimization";
+import { instructionReordering } from "../Optimization/InstructionReordering";
 import {
   CodegenFunction,
   alignObjectMethodScopes,
@@ -204,6 +205,11 @@ function* runWithEnvironment(
   deadCodeElimination(hir);
   yield log({ kind: "hir", name: "DeadCodeElimination", value: hir });
 
+  if (env.config.enableInstructionReordering) {
+    instructionReordering(hir);
+    yield log({ kind: "hir", name: "InstructionReordering", value: hir });
+  }
+
   pruneMaybeThrows(hir);
   yield log({ kind: "hir", name: "PruneMaybeThrows", value: hir });
 

compiler/packages/babel-plugin-react-compiler/src/HIR/Environment.ts

@@ -277,6 +277,12 @@ const EnvironmentConfigSchema = z.object({
 
   enableEmitHookGuards: ExternalFunctionSchema.nullish(),
 
+  /**
+   * Enable instruction reordering. See InstructionReordering.ts for the details
+   * of the approach.
+   */
+  enableInstructionReordering: z.boolean().default(false),
+
   /*
    * Enables instrumentation codegen. This emits a dev-mode only call to an
    * instrumentation function, for components and hooks that Forget compiles.

compiler/packages/babel-plugin-react-compiler/src/HIR/HIR.ts

@@ -335,6 +335,28 @@ export type HIR = {
  * statements and not implicit exceptions which may occur.
  */
 export type BlockKind = "block" | "value" | "loop" | "sequence" | "catch";
+
+/**
+ * Returns true for "block" and "catch" block kinds which correspond to statements
+ * in the source, including BlockStatement, CatchStatement.
+ *
+ * Inverse of isExpressionBlockKind()
+ */
+export function isStatementBlockKind(kind: BlockKind): boolean {
+  return kind === "block" || kind === "catch";
+}
+
+/**
+ * Returns true for "value", "loop", and "sequence" block kinds which correspond to
+ * expressions in the source, such as ConditionalExpression, LogicalExpression, loop
+ * initializer/test/updaters, etc
+ *
+ * Inverse of isStatementBlockKind()
+ */
+export function isExpressionBlockKind(kind: BlockKind): boolean {
+  return !isStatementBlockKind(kind);
+}
+
 export type BasicBlock = {
   kind: BlockKind;
   id: BlockId;