[Coroutines] Don't assert if coro-early runs more than once (llvm#134854)

The pass may run more than once during ThinLTO for example (see bug).
Maybe that means those pass pipelines aren't optimal, but the pass
should be resilient against that.

Fixes llvm#134054

Author: zmodem

llvm/include/llvm/Transforms/Coroutines/CoroInstr.h

@@ -217,8 +217,8 @@ class CoroIdInst : public AnyCoroIdInst {
     return cast<Function>(getArgOperand(CoroutineArg)->stripPointerCasts());
   }
   void setCoroutineSelf() {
-    assert(isa<ConstantPointerNull>(getArgOperand(CoroutineArg)) &&
-           "Coroutine argument is already assigned");
+    if (!isa<ConstantPointerNull>(getArgOperand(CoroutineArg)))
+      assert(getCoroutine() == getFunction() && "Don't change coroutine.");
     setArgOperand(CoroutineArg, getFunction());
   }
 

llvm/test/Transforms/Coroutines/coro-early-twice.ll

@@ -0,0 +1,36 @@
+; RUN: opt < %s -passes='module(coro-early,coro-early)' -S | FileCheck %s
+
+; Check that coro-early can run twice without asserting/crashing.
+
+; CHECK-LABEL: define ptr @f
+; CHECK: call token @llvm.coro.id(i32 0, ptr null, ptr @f, ptr null)
+
+define ptr @f(i32 %n) presplitcoroutine {
+entry:
+  %id = call token @llvm.coro.id(i32 0, ptr null, ptr null, ptr null)
+  %size = call i32 @llvm.coro.size.i32()
+  %alloc = call ptr @malloc(i32 %size)
+  %hdl = call ptr @llvm.coro.begin(token %id, ptr %alloc)
+
+  %sp1 = call i8 @llvm.coro.suspend(token none, i1 false)
+  switch i8 %sp1, label %suspend [i8 0, label %resume1
+                                  i8 1, label %cleanup]
+resume1:
+  br label %cleanup
+cleanup:
+  %mem = call ptr @llvm.coro.free(token %id, ptr %hdl)
+  call void @free(ptr %mem)
+  br label %suspend
+suspend:
+  call i1 @llvm.coro.end(ptr %hdl, i1 0, token none)
+  ret ptr %hdl
+}
+
+declare token @llvm.coro.id(i32, ptr, ptr, ptr)
+declare i32 @llvm.coro.size.i32()
+declare noalias ptr @malloc(i32)
+declare ptr @llvm.coro.begin(token, ptr)
+declare i8  @llvm.coro.suspend(token, i1)
+declare ptr @llvm.coro.free(token, ptr)
+declare void @free(ptr)
+declare i1 @llvm.coro.end(ptr, i1, token)