[simplifycfg][loop-simplify] Preserve loop metadata in 2 transformations.

insertUniqueBackedgeBlock in lib/Transforms/Utils/LoopSimplify.cpp now
propagates existing llvm.loop metadata to newly the added backedge.

llvm::TryToSimplifyUncondBranchFromEmptyBlock in lib/Transforms/Utils/Local.cpp
now propagates existing llvm.loop metadata to the branch instructions in the
predecessor blocks of the empty block that is removed.

Differential Revision: https://reviews.llvm.org/D26495

llvm-svn: 287341
diff --git a/llvm/test/Transforms/LoopSimplify/preserve-llvm-loop-metadata.ll b/llvm/test/Transforms/LoopSimplify/preserve-llvm-loop-metadata.ll
new file mode 100644
index 0000000..bd27794
--- /dev/null
+++ b/llvm/test/Transforms/LoopSimplify/preserve-llvm-loop-metadata.ll
@@ -0,0 +1,42 @@
+; RUN: opt -loop-simplify -S < %s | FileCheck %s
+
+define void @test1(i32 %n) {
+entry:
+  br label %while.cond
+
+while.cond:                                       ; preds = %if.then, %if.else, %entry
+  %count.0 = phi i32 [ 0, %entry ], [ %add, %if.then ], [ %add2, %if.else ]
+  %cmp = icmp ugt i32 %count.0, %n
+  br i1 %cmp, label %while.end, label %while.body
+
+while.body:                                       ; preds = %while.cond
+  %rem = and i32 %count.0, 1
+  %cmp1 = icmp eq i32 %rem, 0
+  br i1 %cmp1, label %if.then, label %if.else
+
+if.then:                                          ; preds = %while.body
+  %add = add i32 %count.0, 1
+  br label %while.cond, !llvm.loop !0
+
+if.else:                                          ; preds = %while.body
+  %add2 = add i32 %count.0, 2
+  br label %while.cond, !llvm.loop !0
+
+while.end:                                        ; preds = %while.cond
+  ret void
+}
+
+; CHECK: if.then
+; CHECK-NOT: br {{.*}}!llvm.loop{{.*}}
+
+; CHECK: while.cond.backedge:
+; CHECK: br label %while.cond, !llvm.loop !0
+
+; CHECK: if.else
+; CHECK-NOT: br {{.*}}!llvm.loop{{.*}}
+
+
+!0 = distinct !{!0, !1}
+!1 = !{!"llvm.loop.distribute.enable", i1 true}
+; CHECK: !0 = distinct !{!0, !1}
+; CHECK: !1 = !{!"llvm.loop.distribute.enable", i1 true}
diff --git a/llvm/test/Transforms/SimplifyCFG/preserve-llvm-loop-metadata.ll b/llvm/test/Transforms/SimplifyCFG/preserve-llvm-loop-metadata.ll
new file mode 100644
index 0000000..12a908b
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/preserve-llvm-loop-metadata.ll
@@ -0,0 +1,53 @@
+; RUN: opt -simplifycfg -S < %s | FileCheck %s
+
+define void @test1(i32 %n) #0 {
+entry:
+  %n.addr = alloca i32, align 4
+  %count = alloca i32, align 4
+  store i32 %n, i32* %n.addr, align 4
+  %0 = bitcast i32* %count to i8*
+  store i32 0, i32* %count, align 4
+  br label %while.cond
+
+while.cond:                                       ; preds = %if.end, %entry
+  %1 = load i32, i32* %count, align 4
+  %2 = load i32, i32* %n.addr, align 4
+  %cmp = icmp ule i32 %1, %2
+  br i1 %cmp, label %while.body, label %while.end
+
+while.body:                                       ; preds = %while.cond
+  %3 = load i32, i32* %count, align 4
+  %rem = urem i32 %3, 2
+  %cmp1 = icmp eq i32 %rem, 0
+  br i1 %cmp1, label %if.then, label %if.else
+
+if.then:                                          ; preds = %while.body
+  %4 = load i32, i32* %count, align 4
+  %add = add i32 %4, 1
+  store i32 %add, i32* %count, align 4
+  br label %if.end
+
+; CHECK: if.then:
+; CHECK:  br label %while.cond, !llvm.loop !0
+
+if.else:                                          ; preds = %while.body
+  %5 = load i32, i32* %count, align 4
+  %add2 = add i32 %5, 2
+  store i32 %add2, i32* %count, align 4
+  br label %if.end
+
+; CHECK: if.else:
+; CHECK:  br label %while.cond, !llvm.loop !0
+
+if.end:                                           ; preds = %if.else, %if.then
+  br label %while.cond, !llvm.loop !0
+
+while.end:                                        ; preds = %while.cond
+  %6 = bitcast i32* %count to i8*
+  ret void
+}
+
+!0 = distinct !{!0, !1}
+!1 = !{!"llvm.loop.distribute.enable", i1 true}
+; CHECK: !0 = distinct !{!0, !1}
+; CHECK: !1 = !{!"llvm.loop.distribute.enable", i1 true}