[llvm] r297254 - Handle UnreachableInst in isGuaranteedToTransferExecutionToSuccessor

[Sebastian Pop via llvm-commits]

Author: spop
Date: Tue Mar  7 19:54:50 2017
New Revision: 297254

URL: http://llvm.org/viewvc/llvm-project?rev=297254&view=rev
Log:
Handle UnreachableInst in isGuaranteedToTransferExecutionToSuccessor

A block with an UnreachableInst does not transfer execution to a successor.
The problem was exposed by GVN-hoist. This patch fixes bug 32153.

Patch by Aditya Kumar.

Differential Revision: https://reviews.llvm.org/D30667

Added:
    llvm/trunk/test/Transforms/GVNHoist/hoist-very-busy.ll
Modified:
    llvm/trunk/lib/Analysis/ValueTracking.cpp

Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=297254&r1=297253&r2=297254&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Tue Mar  7 19:54:50 2017
@@ -3781,6 +3781,8 @@ bool llvm::isGuaranteedToTransferExecuti
     return false;
   if (isa<ReturnInst>(I))
     return false;
+  if (isa<UnreachableInst>(I))
+    return false;
 
   // Calls can throw, or contain an infinite loop, or kill the process.
   if (auto CS = ImmutableCallSite(I)) {

Added: llvm/trunk/test/Transforms/GVNHoist/hoist-very-busy.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVNHoist/hoist-very-busy.ll?rev=297254&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/GVNHoist/hoist-very-busy.ll (added)
+++ llvm/trunk/test/Transforms/GVNHoist/hoist-very-busy.ll Tue Mar  7 19:54:50 2017
@@ -0,0 +1,34 @@
+; RUN: opt -S -gvn-hoist < %s | FileCheck %s
+
+%struct.__jmp_buf_tag = type { [8 x i64], i32 }
+
+; Check that hoisting only happens when the expression is very busy.
+; CHECK: store
+; CHECK: store
+
+ at test_exit_buf = global %struct.__jmp_buf_tag zeroinitializer
+ at G = global i32 0
+
+define void @test_command(i32 %c1) {
+entry:
+  switch i32 %c1, label %exit [
+    i32 0, label %sw0
+    i32 1, label %sw1
+  ]
+
+sw0:
+  store i32 1, i32* @G
+  br label %exit
+
+sw1:
+  store i32 1, i32* @G
+  br label %exit
+
+exit:
+  call void @longjmp(%struct.__jmp_buf_tag* @test_exit_buf, i32 1) #0
+  unreachable
+}
+
+declare void @longjmp(%struct.__jmp_buf_tag*, i32) #0
+
+attributes #0 = { noreturn nounwind }