[PATCH] D129530: [coroutine] add nomerge function attribute to `llvm.coro.save`

[Yuanfang Chen via Phabricator via cfe-commits]

ychen created this revision.
ychen added reviewers: nikic, ChuanqiXu.
Herald added subscribers: jdoerfert, hiraditya.
Herald added a project: All.
ychen requested review of this revision.
Herald added projects: clang, LLVM.
Herald added subscribers: llvm-commits, cfe-commits.

It is illegal to merge two `llvm.coro.save` calls unless their
`llvm.coro.suspend` users are also merged. Marks it "nomerge" for
the moment.

This reverts D129025 <https://reviews.llvm.org/D129025>.

Alternative to D129025 <https://reviews.llvm.org/D129025>, which affects other token type users like WinEH.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D129530

Files:
  clang/test/CodeGenCoroutines/coro-attributes.cpp
  llvm/docs/Coroutines.rst
  llvm/include/llvm/IR/Intrinsics.td
  llvm/lib/Transforms/Utils/SimplifyCFG.cpp
  llvm/test/Transforms/SimplifyCFG/hoist-skip-token.ll


Index: llvm/test/Transforms/SimplifyCFG/hoist-skip-token.ll
===================================================================
--- llvm/test/Transforms/SimplifyCFG/hoist-skip-token.ll
+++ llvm/test/Transforms/SimplifyCFG/hoist-skip-token.ll
@@ -1,7 +1,7 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -passes='simplifycfg<hoist-common-insts>' -S | FileCheck %s
 
-declare token @llvm.coro.save(ptr)
+declare token @llvm.coro.save(ptr) #0
 declare i8 @llvm.coro.suspend(token, i1)
 
 define void @f(i32 %x) {
@@ -37,3 +37,5 @@
 coro.ret:
   ret void
 }
+
+attributes #0 = { nomerge }
Index: llvm/lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1499,10 +1499,6 @@
     if (I1->isTerminator())
       goto HoistTerminator;
 
-    // Hoisting token-returning instructions would obscure the origin.
-    if (I1->getType()->isTokenTy())
-      return Changed;
-
     // If we're going to hoist a call, make sure that the two instructions we're
     // commoning/hoisting are both marked with musttail, or neither of them is
     // marked as such. Otherwise, we might end up in a situation where we hoist
Index: llvm/include/llvm/IR/Intrinsics.td
===================================================================
--- llvm/include/llvm/IR/Intrinsics.td
+++ llvm/include/llvm/IR/Intrinsics.td
@@ -1308,7 +1308,7 @@
 def int_coro_size : Intrinsic<[llvm_anyint_ty], [], [IntrNoMem]>;
 def int_coro_align : Intrinsic<[llvm_anyint_ty], [], [IntrNoMem]>;
 
-def int_coro_save : Intrinsic<[llvm_token_ty], [llvm_ptr_ty], []>;
+def int_coro_save : Intrinsic<[llvm_token_ty], [llvm_ptr_ty], [IntrNoMerge]>;
 def int_coro_suspend : Intrinsic<[llvm_i8_ty], [llvm_token_ty, llvm_i1_ty], []>;
 def int_coro_suspend_retcon : Intrinsic<[llvm_any_ty], [llvm_vararg_ty], []>;
 def int_coro_prepare_retcon : Intrinsic<[llvm_ptr_ty], [llvm_ptr_ty],
Index: llvm/docs/Coroutines.rst
===================================================================
--- llvm/docs/Coroutines.rst
+++ llvm/docs/Coroutines.rst
@@ -1555,7 +1555,9 @@
 
 The '``llvm.coro.save``' marks the point where a coroutine need to update its
 state to prepare for resumption to be considered suspended (and thus eligible
-for resumption).
+for resumption). It is illegal to merge two '``llvm.coro.save``' calls unless their
+'``llvm.coro.suspend``' users are also merged. So '``llvm.coro.save``' is currently
+tagged with the `no_merge` function attribute.
 
 Arguments:
 """"""""""
Index: clang/test/CodeGenCoroutines/coro-attributes.cpp
===================================================================
--- clang/test/CodeGenCoroutines/coro-attributes.cpp
+++ clang/test/CodeGenCoroutines/coro-attributes.cpp
@@ -14,7 +14,9 @@
 };
 
 // CHECK: void @_Z3foov() #[[FOO_ATTR_NUM:[0-9]+]]
+// CHECK: declare token @llvm.coro.save(ptr) #[[SAVE_ATTR_NUM:[0-9]+]]
 // CHECK: attributes #[[FOO_ATTR_NUM]] = { {{.*}} presplitcoroutine
+// CHECK: attributes #[[SAVE_ATTR_NUM]] = { {{.*}}nomerge
 coro foo() {
   co_await suspend_always{};
 }


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