From b170d856a3a303ab826f6896812bfd0ce05ec706 Mon Sep 17 00:00:00 2001
From: Yuanfang Chen <yuanfang.chen@sony.com>
Date: Tue, 5 Jul 2022 10:56:19 -0700
Subject: [PATCH] [SimplifyCFG] Skip hoisting common instructions that return
 token type

By LangRef, hoisting token-returning instructions obsures the origin
so it should be skipped. Found this issue while investigating a
CoroSplit pass crash.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D129025
---
 llvm/lib/Transforms/Utils/SimplifyCFG.cpp          |  4 +++
 .../Transforms/SimplifyCFG/hoist-skip-token.ll     | 39 ++++++++++++++++++++++
 2 files changed, 43 insertions(+)
 create mode 100644 llvm/test/Transforms/SimplifyCFG/hoist-skip-token.ll

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 6b0f1e3..653ebd9 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1505,6 +1505,10 @@ bool SimplifyCFGOpt::HoistThenElseCodeToIf(BranchInst *BI,
     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
diff --git a/llvm/test/Transforms/SimplifyCFG/hoist-skip-token.ll b/llvm/test/Transforms/SimplifyCFG/hoist-skip-token.ll
new file mode 100644
index 0000000..1e9dc25
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/hoist-skip-token.ll
@@ -0,0 +1,39 @@
+; 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 i8 @llvm.coro.suspend(token, i1)
+
+define void @f(i32 %x) {
+; CHECK-LABEL: @f(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 0
+; CHECK-NEXT:    br i1 [[CMP]], label [[AWAIT_SUSPEND:%.*]], label [[FINAL_SUSPEND:%.*]]
+; CHECK:       await.suspend:
+; CHECK-NEXT:    [[TMP0:%.*]] = call token @llvm.coro.save(ptr null)
+; CHECK-NEXT:    [[TMP1:%.*]] = call i8 @llvm.coro.suspend(token [[TMP0]], i1 false)
+; CHECK-NEXT:    br label [[CORO_RET:%.*]]
+; CHECK:       final.suspend:
+; CHECK-NEXT:    [[TMP2:%.*]] = call token @llvm.coro.save(ptr null)
+; CHECK-NEXT:    [[TMP3:%.*]] = call i8 @llvm.coro.suspend(token [[TMP2]], i1 true)
+; CHECK-NEXT:    br label [[CORO_RET]]
+; CHECK:       coro.ret:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp = icmp slt i32 %x, 0
+  br i1 %cmp, label %await.suspend, label %final.suspend
+
+await.suspend:
+  %0 = call token @llvm.coro.save(ptr null)
+  %1 = call i8 @llvm.coro.suspend(token %0, i1 false)
+  br label %coro.ret
+
+final.suspend:
+  %2 = call token @llvm.coro.save(ptr null)
+  %3 = call i8 @llvm.coro.suspend(token %2, i1 true)
+  br label %coro.ret
+
+coro.ret:
+  ret void
+}
-- 
2.7.4