[PATCH] D57978: [CodeGen] Generate follow-up metadata for loops with more than one transformation.

[Michael Kruse via Phabricator via cfe-commits]

Meinersbur added a comment.

In D57978#1440894 <https://reviews.llvm.org/D57978#1440894>, @dmgreen wrote:

> This could maybe do with a few extra tests. Am I correct in saying something like this:
>
>   #pragma unroll_and_jam(4)
>   for(int j = 0; j < n; j++) {
>     #pragma unroll(4)
>     for(int k = 0; k < n; k++) {
>       x[j*n+k] = 10;
>     }
>   }
>
>
> would end up with a llvm.loop.unroll_and_jam.followup_inner with a llvm.loop.unroll_count?


correct. I added a new test `pragma-followup_inner.cpp` where this can be seen.



================
Comment at: lib/CodeGen/CGLoopInfo.cpp:500
+    // Unroll-and-jam of an inner loop and unroll-and-jam of the same loop as
+    // the outer loop does not make much sense, but we have to pick an order.
+    AfterJam.UnrollAndJamCount = Attrs.UnrollAndJamCount;
----------------
dmgreen wrote:
> I was having trouble parsing this sentance. Does it mean both the inner loop and the outer loop both have unroll-and-jam? UnrollAndJam processes loops from inner to outer, so if this is working as I think, maybe it should be put into BeforeJam.
> Does it mean both the inner loop and the outer loop both have unroll-and-jam? 

Correct. I was thinking of such a case:
```
#pragma unroll_and_jam(2)
for (int i = 0; i < m; i+=1)
  #pragma unroll_and_jam(3)
  for (int j = 0; j < n; j+=1)
```

Assuming the inner unroll-and-jam would do something, would it happen before or after the outer transformation. As you mentioned, there is an argument to put it into `BeforeJam`. Changed.


================
Comment at: lib/CodeGen/CGLoopInfo.cpp:502
+    AfterJam.UnrollAndJamCount = Attrs.UnrollAndJamCount;
+    AfterJam.UnrollAndJamEnable = AfterJam.UnrollAndJamEnable;
+
----------------
dmgreen wrote:
>  = Attrs.UnrollAndJamEnable ?
thanks


Repository:
  rC Clang

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  https://reviews.llvm.org/D57978/new/

https://reviews.llvm.org/D57978