[hir] Validate globals are equal before propagating

Make sure the value of the globals in phi operands are the same before constant 
propagating them.

compiler/forget/packages/babel-plugin-react-forget/src/Optimization/ConstantPropagation.ts

@@ -206,6 +206,19 @@ function evaluatePhi(phi: Phi, constants: Constants): Constant | null {
         }
         break;
       }
+      case "LoadGlobal": {
+        CompilerError.invariant(value.kind === "LoadGlobal", {
+          reason: "value kind expected to be LoadGlobal",
+          loc: null,
+          suggestions: null,
+        });
+
+        // different global values, can't constant propogate
+        if (operandValue.name !== value.name) {
+          return null;
+        }
+        break;
+      }
       default:
         return null;
     }

compiler/forget/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/constant-propagate-global-phis-constant.expect.md

@@ -0,0 +1,33 @@
+
+## Input
+
+```javascript
+function Test() {
+  const { tab } = useFoo();
+  const currentTab = tab === WAT ? WAT : WAT;
+
+  return <Foo value={currentTab} />;
+}
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+function Test() {
+  const $ = useMemoCache(1);
+  const { tab } = useFoo();
+  tab === WAT ? WAT : WAT;
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = <Foo value={WAT} />;
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+```
+      

compiler/forget/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/constant-propagate-global-phis-constant.js

@@ -0,0 +1,6 @@
+function Test() {
+  const { tab } = useFoo();
+  const currentTab = tab === WAT ? WAT : WAT;
+
+  return <Foo value={currentTab} />;
+}