[LoopVectorize] Keep hints from original loop on the vector loop

We need to keep loop hints from the original loop on the new vector loop.
Failure to do this meant that, for example:

  void foo(int *b) {
  #pragma clang loop unroll(disable)
    for (int i = 0; i < 16; ++i)
      b[i] = 1;
  }

this loop would be unrolled. Why? Because we'd vectorize it, thus dropping the
hints that unrolling should be disabled, and then we'd unroll it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267970 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp
index 4a51fc9..c993d2a 100644 (file)
--- a/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -3200,6 +3200,11 @@ void InnerLoopVectorizer::createEmptyLoop() {
   LoopVectorBody.push_back(VecBody);
   LoopScalarBody = OldBasicBlock;
 
+  // Keep all loop hints from the original loop on the vector loop (we'll
+  // replace the vectorizer-specific hints below).
+  if (MDNode *LID = OrigLoop->getLoopID())
+    Lp->setLoopID(LID);
+
   LoopVectorizeHints Hints(Lp, true);
   Hints.setAlreadyVectorized();
 }

diff --git a/test/Transforms/LoopVectorize/hints-trans.ll b/test/Transforms/LoopVectorize/hints-trans.ll
new file mode 100644 (file)
index 0000000..ec5ddbb
--- /dev/null
+++ b/test/Transforms/LoopVectorize/hints-trans.ll
@@ -0,0 +1,30 @@
+; RUN: opt -S -loop-vectorize -force-vector-interleave=1 -force-vector-width=4 -instsimplify -simplifycfg < %s | FileCheck %s
+; Note: -instsimplify -simplifycfg remove the (now dead) original loop, making
+; it easy to test that the llvm.loop.unroll.disable hint is still present.
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: norecurse nounwind uwtable
+define void @foo(i32* nocapture %b) #0 {
+entry:
+  br label %for.body
+
+for.cond.cleanup:                                 ; preds = %for.body
+  ret void
+
+for.body:                                         ; preds = %for.body, %entry
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %arrayidx = getelementptr inbounds i32, i32* %b, i64 %indvars.iv
+  store i32 1, i32* %arrayidx, align 4
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp eq i64 %indvars.iv.next, 16
+  br i1 %exitcond, label %for.cond.cleanup, label %for.body, !llvm.loop !0
+}
+
+; CHECK-LABEL: @foo
+; CHECK: = !{!"llvm.loop.unroll.disable"}
+
+attributes #0 = { norecurse nounwind uwtable }
+
+!0 = distinct !{!0, !1}
+!1 = !{!"llvm.loop.unroll.disable"}