[llvm] r267970 - [LoopVectorize] Keep hints from original loop on the vector loop

[Hal Finkel via llvm-commits]

Author: hfinkel
Date: Thu Apr 28 20:27:40 2016
New Revision: 267970

URL: http://llvm.org/viewvc/llvm-project?rev=267970&view=rev
Log:
[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.

Added:
    llvm/trunk/test/Transforms/LoopVectorize/hints-trans.ll
Modified:
    llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp

Modified: llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp?rev=267970&r1=267969&r2=267970&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp (original)
+++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp Thu Apr 28 20:27:40 2016
@@ -3200,6 +3200,11 @@ void InnerLoopVectorizer::createEmptyLoo
   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();
 }

Added: llvm/trunk/test/Transforms/LoopVectorize/hints-trans.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/hints-trans.ll?rev=267970&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/hints-trans.ll (added)
+++ llvm/trunk/test/Transforms/LoopVectorize/hints-trans.ll Thu Apr 28 20:27:40 2016
@@ -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"}