[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

1 files changed, 42 insertions, 0 deletions

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 00000000000..bd27794d193
--- /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}