From 57e487e92c68437792c2d6f7e69f1d08164992ce Mon Sep 17 00:00:00 2001
From: Owen Anderson <resistor@mac.com>
Date: Mon, 1 Jun 2015 17:20:31 +0000
Subject: [PATCH] Teach the IR Sink pass to (conservatively) respect convergent
 annotations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238762 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/Sink.cpp     |  6 ++++++
 test/Transforms/Sink/convergent.ll | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+)
 create mode 100644 test/Transforms/Sink/convergent.ll

diff --git a/lib/Transforms/Scalar/Sink.cpp b/lib/Transforms/Scalar/Sink.cpp
index b169d5612f0..ec3a0186641 100644
--- a/lib/Transforms/Scalar/Sink.cpp
+++ b/lib/Transforms/Scalar/Sink.cpp
@@ -172,6 +172,12 @@ static bool isSafeToMove(Instruction *Inst, AliasAnalysis *AA,
   if (isa<TerminatorInst>(Inst) || isa<PHINode>(Inst))
     return false;
 
+  // Convergent operations can only be moved to control equivalent blocks.
+  if (auto CS = CallSite(Inst)) {
+    if (CS.hasFnAttr(Attribute::Convergent))
+      return false;
+  }
+
   return true;
 }
 
diff --git a/test/Transforms/Sink/convergent.ll b/test/Transforms/Sink/convergent.ll
new file mode 100644
index 00000000000..49207dbc992
--- /dev/null
+++ b/test/Transforms/Sink/convergent.ll
@@ -0,0 +1,24 @@
+; RUN: opt -sink -S < %s | FileCheck %s
+
+; Verify that IR sinking does not move convergent operations to
+; blocks that are not control equivalent.
+
+; CHECK: define i32 @foo
+; CHECK: entry
+; CHECK-NEXT: call i32 @bar
+; CHECK-NEXT: br i1 %arg
+
+define i32 @foo(i1 %arg) {
+entry:
+  %c = call i32 @bar() readonly convergent
+  br i1 %arg, label %then, label %end
+
+then:
+  ret i32 %c
+
+end:
+  ret i32 0
+}
+
+declare i32 @bar() readonly convergent
+
-- 
2.34.1