[AMD] Add messages for debugging BlockPingpong (#8804)

For some num_warps, num_stages and tile_size, BlockPingpong will exit
early without leaving a message.
Added message for these cases so people can be aware that pingpong
wasn't really involved. Also add some transparency for debugging. This
shouldn't change the way how BlockPingong or anything else in Triton is
used.


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# New contributor declaration
- [X] I am not making a trivial change, such as fixing a typo in a
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- Select one of the following.
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make sure BlockPingpong won't silently exit early, making it easier to
debug`.

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Co-authored-by: Peiying Hua <[email protected]>

Author: peiying779

third_party/amd/lib/TritonAMDGPUTransforms/BlockPingpong.cpp

@@ -1185,8 +1185,19 @@ void Pingponger::getDotPingponged() {
     // times for issuing the memory operations and issuing dot operations,
     // smaller tile sizes are not likely to get any advantage from current dot
     // centric pingpong scheduling.
-    if (tileSize <= smallTile && tileSize >= minTile)
+    if (tileSize <= smallTile && tileSize >= minTile) {
       transformOnePPClusters(builder, loc);
+      LDBG("Pingpong scheduling applied for numWarps=4 with tileSize=" +
+           std::to_string(tileSize) + " (in range [" + std::to_string(minTile) +
+           ", " + std::to_string(smallTile) +
+           "]), One Dot-Memory (ping-pong) cluster used.");
+    } else {
+      std::stringstream message;
+      message << "Skipping pingpong for numWarps=4: tileSize=" << tileSize
+              << " is outside the range [" << minTile << ", " << smallTile
+              << "]";
+      LDBG(message.str());
+    }
     // numWarps=4 doesn't need asymmetric sync, return.
     return;
   } else if (numWarps == 8 && numStages == 2) {
@@ -1216,8 +1227,15 @@ void Pingponger::getDotPingponged() {
              "cluster transformation");
         return;
       }
-    } else
+    } else {
+      std::stringstream message;
+      message << "Skipping pingpong for numWarps=8, numStages=2: tileSize="
+              << tileSize
+              << " does not match supported tile sizes (medium=" << mediumTile
+              << " or large=" << largeTile << ")";
+      LDBG(message.str());
       return;
+    }
 
     // Let half of the warps start the loop first and the others follow later
     // but in the synchronized way. This can be accomplished by calling