[llvm] r357483 - [PruneEH] Don't split musttail call from ret

[Joseph Tremoulet via llvm-commits]

Author: josepht
Date: Tue Apr  2 08:47:11 2019
New Revision: 357483

URL: http://llvm.org/viewvc/llvm-project?rev=357483&view=rev
Log:
[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

Added:
    llvm/trunk/test/Transforms/PruneEH/musttail.ll
Modified:
    llvm/trunk/lib/Transforms/IPO/PruneEH.cpp

Modified: llvm/trunk/lib/Transforms/IPO/PruneEH.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/PruneEH.cpp?rev=357483&r1=357482&r2=357483&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/PruneEH.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/PruneEH.cpp Tue Apr  2 08:47:11 2019
@@ -203,7 +203,8 @@ static bool SimplifyFunction(Function *F
 
     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

Added: llvm/trunk/test/Transforms/PruneEH/musttail.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/PruneEH/musttail.ll?rev=357483&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/PruneEH/musttail.ll (added)
+++ llvm/trunk/test/Transforms/PruneEH/musttail.ll Tue Apr  2 08:47:11 2019
@@ -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 }