From: Joseph Tremoulet <jotrem@microsoft.com>
Date: Tue, 2 Apr 2019 15:47:11 +0000 (+0000)
Subject: [PruneEH] Don't split musttail call from ret
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=5fc1c8d59b35c30ee9912e06894612c177465415;p=llvm

[PruneEH] Don't split musttail call from ret

Summary:
When inserting an `unreachable` after a noreturn call, we must ensure
that it's not a musttail call to avoid breaking the IR invariants for
musttail calls.

Reviewers: fedor.sergeev, majnemer

Reviewed By: majnemer

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60079

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@357483 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/IPO/PruneEH.cpp b/lib/Transforms/IPO/PruneEH.cpp
index 46d42764fd2..ef7b43e8b55 100644
--- a/lib/Transforms/IPO/PruneEH.cpp
+++ b/lib/Transforms/IPO/PruneEH.cpp
@@ -203,7 +203,8 @@ static bool SimplifyFunction(Function *F, CallGraph &CG) {
 
     for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; )
       if (CallInst *CI = dyn_cast<CallInst>(I++))
-        if (CI->doesNotReturn() && !isa<UnreachableInst>(I)) {
+        if (CI->doesNotReturn() && !CI->isMustTailCall() &&
+            !isa<UnreachableInst>(I)) {
           // This call calls a function that cannot return.  Insert an
           // unreachable instruction after it and simplify the code.  Do this
           // by splitting the BB, adding the unreachable, then deleting the
diff --git a/test/Transforms/PruneEH/musttail.ll b/test/Transforms/PruneEH/musttail.ll
new file mode 100644
index 00000000000..1ad607713c6
--- /dev/null
+++ b/test/Transforms/PruneEH/musttail.ll
@@ -0,0 +1,15 @@
+; RUN: opt -prune-eh -S < %s | FileCheck %s
+
+declare void @noreturn()
+
+define void @testfn() {
+    ; A musttail call must be followed by (optional bitcast then) ret,
+    ; so make sure we don't insert an unreachable
+    ; CHECK: musttail call void @noreturn
+    ; CHECK-NOT: unreachable
+    ; CHECK-NEXT: ret void
+    musttail call void @noreturn() #0
+    ret void
+}
+
+attributes #0 = { noreturn }