[PATCH] Make the MemDepPrinter to print something

[Dmitry Mikushin]

  Hi Dan,

  OK, I missed that because other `-print-*` passes are just printing to stderr without `-analyze`... So is `-analyze` necessary?

  Also, I have a question: why for the store from 2 loads in the IR code below I get store having only single Def dependency on one of the loads, not on both of them?

  Thanks,
  - D.



    define void @vector_sum(i32 %length, float* nocapture readonly %in1, float* nocapture readonly %in2, float* nocapture %out) #0 {
    entry:
      %cmp9 = icmp sgt i32 %length, 0
      br i1 %cmp9, label %for.body, label %for.end

    for.body:                     ; preds = %entry, %for.body
      %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
      %arrayidx = getelementptr inbounds float* %in1, i64 %indvars.iv
      %0 = load float* %arrayidx, align 4, !tbaa !1
      %arrayidx2 = getelementptr inbounds float* %in2, i64 %indvars.iv
      %1 = load float* %arrayidx2, align 4, !tbaa !1
      %add = fadd float %0, %1
      %arrayidx4 = getelementptr inbounds float* %out, i64 %indvars.iv
      store float %add, float* %arrayidx4, align 4, !tbaa !1
      %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
      %lftr.wideiv = trunc i64 %indvars.iv.next to i32
      %exitcond = icmp eq i32 %lftr.wideiv, %length
      br i1 %exitcond, label %for.end, label %for.body

    for.end:                      ; preds = %for.body, %entry
      ret void
    }

    $ clang -emit-llvm example.c -O1 -S -o - | opt -memdep -print-memdeps -o /dev/null

    Function vector_sum memory dependencies:

        Unknown in block %for.body
        Unknown in block %entry
      %0 = load float* %arrayidx, align 4, !tbaa !1

        Unknown in block %for.body
        Unknown in block %entry
      %1 = load float* %arrayidx2, align 4, !tbaa !1

        Def from:   %1 = load float* %arrayidx2, align 4, !tbaa !1
      store float %add, float* %arrayidx4, align 4, !tbaa !1

http://llvm-reviews.chandlerc.com/D2333

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