[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: fe01f94e186e62171e7cc82e10d7864c48f932be
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,
@@ -71,6 +72,7 @@ import {
 import { alignMethodCallScopes } from "../ReactiveScopes/AlignMethodCallScopes";
 import { alignReactiveScopesToBlockScopesHIR } from "../ReactiveScopes/AlignReactiveScopesToBlockScopesHIR";
 import { pruneAlwaysInvalidatingScopes } from "../ReactiveScopes/PruneAlwaysInvalidatingScopes";
+import pruneInitializationDependencies from "../ReactiveScopes/PruneInitializationDependencies";
 import { stabilizeBlockIds } from "../ReactiveScopes/StabilizeBlockIds";
 import { eliminateRedundantPhi, enterSSA, leaveSSA } from "../SSA";
 import { inferTypes } from "../TypeInference";
@@ -91,7 +93,6 @@ import {
   validatePreservedManualMemoization,
   validateUseMemo,
 } from "../Validation";
-import pruneInitializationDependencies from "../ReactiveScopes/PruneInitializationDependencies";
 
 export type CompilerPipelineValue =
   | { kind: "ast"; name: string; value: CodegenFunction }
@@ -202,6 +203,9 @@ function* runWithEnvironment(
   deadCodeElimination(hir);
   yield log({ kind: "hir", name: "DeadCodeElimination", value: hir });
 
+  instructionReordering(hir);
+  yield log({ kind: "hir", name: "InstructionReordering", value: hir });
+
   pruneMaybeThrows(hir);
   yield log({ kind: "hir", name: "PruneMaybeThrows", value: hir });