[PATCH] D45066: [Polly] [ScopInfo] Remove bail out condition in buildMinMaxAccess()

Wed Apr 18 15:15:08 PDT 2018

Meinersbur added a comment.

As discussed, here is a test-case. It was more difficult than I originally thought because ScalarEvolution does not support plain `select` (Array subscripts must be SCEVs). Using JScop-import also was no solution because Polly does not create new aliasing expressions after the import.  I used `smax` expressions instead, which `SCEVAffinator` produces piecewise `pw_aff`s. `polly::simplify` must also not coalesce these sets after `remove_divs()` and `range()` (it does still coalesces some of them), and I need at least 9 pieces.

name=test/ScopInfo/piecewise_aliasing.ll
  ; RUN: opt %loadPolly -polly-scops -analyze < %s
  ;
  define void @func(i64 %n, double* nonnull %A, double* nonnull %B, i64 %d) {
  entry:
    br label %for

  for:
    %j = phi i64 [0, %entry], [%j.inc, %inc]
    %j.cmp = icmp slt i64 %j, %n
    br i1 %j.cmp, label %body, label %exit

      body:
        %add.i.i = add nsw i64 1, %j
        %sub.i.i = sub nsw i64 %add.i.i, 1
        %cmp.i.i.i = icmp sgt i64 %sub.i.i, 0
        %cond.i.i.i = select i1 %cmp.i.i.i, i64 %sub.i.i, i64 0
        %mul.i.i = mul nsw i64 %cond.i.i.i, 7
        %sub1.i.i = sub nsw i64 1, %j
        %add2.i.i = add nsw i64 %sub1.i.i, 1
        %cmp.i8.i.i = icmp sgt i64 %add2.i.i, 0
        %cond.i11.i.i = select i1 %cmp.i8.i.i, i64 %add2.i.i, i64 0
        %mul4.i.i = mul nsw i64 %cond.i11.i.i, 7
        %add5.i.i = add nsw i64 %mul.i.i, %mul4.i.i
        %add.i113.i = add nsw i64 1, %j
        %sub.i114.i = sub nsw i64 %add.i113.i, 3
        %cmp.i.i115.i = icmp sgt i64 %sub.i114.i, 0
        %cond.i.i118.i = select i1 %cmp.i.i115.i, i64 %sub.i114.i, i64 0
        %mul.i119.i = mul nsw i64 %cond.i.i118.i, 9
        %sub1.i120.i = sub nsw i64 1, %j
        %add2.i121.i = add nsw i64 %sub1.i120.i, 3
        %cmp.i8.i122.i = icmp sgt i64 %add2.i121.i, 0
        %cond.i11.i126.i = select i1 %cmp.i8.i122.i, i64 %add2.i121.i, i64 0
        %mul4.i127.i = mul nsw i64 %cond.i11.i126.i, 9
        %add5.i128.i = add nsw i64 %mul.i119.i, %mul4.i127.i
        %add.i = add nsw i64 %add5.i.i, %add5.i128.i
        %add.i89.i = add nsw i64 1, %j
        %sub.i90.i = sub nsw i64 %add.i89.i, 4
        %cmp.i.i91.i = icmp sgt i64 %sub.i90.i, 0
        %cond.i.i94.i = select i1 %cmp.i.i91.i, i64 %sub.i90.i, i64 0
        %mul.i95.i = mul nsw i64 %cond.i.i94.i, 11
        %sub1.i96.i = sub nsw i64 1, %j
        %add2.i97.i = add nsw i64 %sub1.i96.i, 4
        %cmp.i8.i98.i = icmp sgt i64 %add2.i97.i, 0
        %cond.i11.i102.i = select i1 %cmp.i8.i98.i, i64 %add2.i97.i, i64 0
        %mul4.i103.i = mul nsw i64 %cond.i11.i102.i, 11
        %add5.i104.i = add nsw i64 %mul.i95.i, %mul4.i103.i
        %add3.i = add nsw i64 %add.i, %add5.i104.i
        %add.i65.i = add nsw i64 1, %j
        %sub.i66.i = sub nsw i64 %add.i65.i, 6
        %cmp.i.i67.i = icmp sgt i64 %sub.i66.i, 0
        %cond.i.i70.i = select i1 %cmp.i.i67.i, i64 %sub.i66.i, i64 0
        %mul.i71.i = mul nsw i64 %cond.i.i70.i, 13
        %sub1.i72.i = sub nsw i64 1, %j
        %add2.i73.i = add nsw i64 %sub1.i72.i, 6
        %cmp.i8.i74.i = icmp sgt i64 %add2.i73.i, 0
        %cond.i11.i78.i = select i1 %cmp.i8.i74.i, i64 %add2.i73.i, i64 0
        %mul4.i79.i = mul nsw i64 %cond.i11.i78.i, 13
        %add5.i80.i = add nsw i64 %mul.i71.i, %mul4.i79.i
        %add5.i = add nsw i64 %add3.i, %add5.i80.i
        %add.i41.i = add nsw i64 1, %j
        %sub.i42.i = sub nsw i64 %add.i41.i, 8
        %cmp.i.i43.i = icmp sgt i64 %sub.i42.i, 0
        %cond.i.i46.i = select i1 %cmp.i.i43.i, i64 %sub.i42.i, i64 0
        %mul.i47.i = mul nsw i64 %cond.i.i46.i, 17
        %sub1.i48.i = sub nsw i64 1, %j
        %add2.i49.i = add nsw i64 %sub1.i48.i, 8
        %cmp.i8.i50.i = icmp sgt i64 %add2.i49.i, 0
        %cond.i11.i54.i = select i1 %cmp.i8.i50.i, i64 %add2.i49.i, i64 0
        %mul4.i55.i = mul nsw i64 %cond.i11.i54.i, 17
        %add5.i56.i = add nsw i64 %mul.i47.i, %mul4.i55.i
        %add7.i = add nsw i64 %add5.i, %add5.i56.i
        %add.i17.i = add nsw i64 1, %j
        %sub.i18.i = sub nsw i64 %add.i17.i, 10
        %cmp.i.i19.i = icmp sgt i64 %sub.i18.i, 0
        %cond.i.i22.i = select i1 %cmp.i.i19.i, i64 %sub.i18.i, i64 0
        %mul.i23.i = mul nsw i64 %cond.i.i22.i, 19
        %sub1.i24.i = sub nsw i64 1, %j
        %add2.i25.i = add nsw i64 %sub1.i24.i, 10
        %cmp.i8.i26.i = icmp sgt i64 %add2.i25.i, 0
        %cond.i11.i30.i = select i1 %cmp.i8.i26.i, i64 %add2.i25.i, i64 0
        %mul4.i31.i = mul nsw i64 %cond.i11.i30.i, 19
        %add5.i32.i = add nsw i64 %mul.i23.i, %mul4.i31.i
        %idxprom = add nsw i64 %add7.i, %add5.i32.i

        %A_idx = getelementptr inbounds double, double* %A, i64 %idxprom
        %val = load double, double* %A_idx
        %B_idx = getelementptr inbounds double, double* %B, i64 %j
        store double %val, double* %B_idx
        br label %inc

  inc:
    %j.inc = add nuw nsw i64 %j, 1
    br label %for

  exit:
    br label %return

  return:
    ret void
  }

With the current Polly, ScopInfo bails out:

  NOTE: Run time checks for %for---%return could not be created as the number of parameters involved is too high. The SCoP will be dismissed.

(yes, the debug message is still misleading)

The set the example produces is:

  [n] -> {
    MemRef_A[274] : n >= 8;
    MemRef_A[283] : n >= 7;
    MemRef_A[292] : n >= 6;
    MemRef_A[295] : n >= 9;
    MemRef_A[316] : n >= 10;
    MemRef_A[325] : n >= 5;
    MemRef_A[367] : n >= 4;
    MemRef_A[373] : n >= 11;
    MemRef_A[i0] : i0 >= 420 and 627 - 69n <= i0 <= 558;
    MemRef_A[i0] : 430 <= i0 <= -482 + 76n
  }

(10 pieces)

After `simple_hull()`, this should be the result:

  [n] -> {
    MemRef_A[i0] : i0 >= 274 and 627 - 69n <= i0 <= 482 + 76n
  }

which is bounded for each n and simple enough for lexmin/-max to process.

@cs15btech11044: Do you have everything to make a test-case for this patch out of it?

Repository:
  rPLO Polly

https://reviews.llvm.org/D45066