[LoopUnswitch] Preserve make.implicit metadata for unswitched conditions

Summary: This patch adds support to preserve make.implicit metadata for unswitched conditions in loop pre-header.

Reviewers: sanjoy, weimingz

Subscribers: mcrosier, llvm-commits

Differential Revision: http://reviews.llvm.org/D11769

llvm-svn: 244132

2 files changed, 24 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
index 934e1619619..2b29fdaebad 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -657,6 +657,7 @@ static void copyMetadata(Instruction *DstInst, const Instruction *SrcInst,
         }
       }
       // fallthrough.
+    case LLVMContext::MD_make_implicit:
     case LLVMContext::MD_dbg:
       DstInst->setMetadata(MD.first, MD.second);
     }
diff --git a/llvm/test/Transforms/LoopUnswitch/copy-metadata.ll b/llvm/test/Transforms/LoopUnswitch/copy-metadata.ll
new file mode 100644
index 00000000000..2a634c25a23
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnswitch/copy-metadata.ll
@@ -0,0 +1,23 @@
+; RUN: opt < %s -loop-unswitch -S < %s 2>&1 | FileCheck %s
+
+; This test checks if unswitched condition preserve make.implicit metadata.
+
+define i32 @test(i1 %cond) {
+; CHECK: br i1 %cond, label %..split_crit_edge, label %.loop_exit.split_crit_edge, !make.implicit !0
+  br label %loop_begin
+
+loop_begin:
+; CHECK: br i1 true, label %continue, label %loop_exit, !make.implicit !0
+  br i1 %cond, label %continue, label %loop_exit, !make.implicit !0
+
+continue:
+  call void @some_func()
+  br label %loop_begin
+
+loop_exit:
+  ret i32 0
+}
+
+declare void @some_func()
+
+!0 = !{}