[Mlir-commits] [mlir] [vector][distribution] Bug fix in `moveRegionToNewWarpOpAndAppendReturns` (PR #153656)

[Charitha Saumya]

https://github.com/charithaintc updated https://github.com/llvm/llvm-project/pull/153656

>From 2ad884cb91dad7ee77ef39cec80edf242a1aba71 Mon Sep 17 00:00:00 2001
From: Charitha Saumya <charitha.saumya.gusthinna.waduge at intel.com>
Date: Wed, 13 Aug 2025 23:57:56 +0000
Subject: [PATCH 1/2] bug fix

---
 .../Dialect/GPU/Utils/DistributionUtils.cpp   | 32 +++++++++++--------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/mlir/lib/Dialect/GPU/Utils/DistributionUtils.cpp b/mlir/lib/Dialect/GPU/Utils/DistributionUtils.cpp
index 384d1a0ddccd2..be71bd02fc43b 100644
--- a/mlir/lib/Dialect/GPU/Utils/DistributionUtils.cpp
+++ b/mlir/lib/Dialect/GPU/Utils/DistributionUtils.cpp
@@ -14,6 +14,7 @@
 #include "mlir/Dialect/Affine/IR/AffineOps.h"
 #include "mlir/Dialect/Arith/IR/Arith.h"
 #include "mlir/IR/Value.h"
+#include "llvm/ADT/DenseMap.h"
 
 #include <numeric>
 
@@ -57,26 +58,29 @@ WarpDistributionPattern::moveRegionToNewWarpOpAndAppendReturns(
                           warpOp.getResultTypes().end());
   auto yield = cast<gpu::YieldOp>(
       warpOp.getBodyRegion().getBlocks().begin()->getTerminator());
-  llvm::SmallSetVector<Value, 32> yieldValues(yield.getOperands().begin(),
-                                              yield.getOperands().end());
+  SmallVector<Value> yieldValues(yield.getOperands().begin(),
+                                 yield.getOperands().end());
+  llvm::SmallDenseMap<Value, unsigned> indexLookup;
+  // Record the value -> first index mapping for faster lookup.
+  for (auto [i, v] : llvm::enumerate(yieldValues)) {
+    if (!indexLookup.count(v))
+      indexLookup[v] = i;
+  }
+
   for (auto [value, type] : llvm::zip_equal(newYieldedValues, newReturnTypes)) {
-    if (yieldValues.insert(value)) {
+    // If the value already exists in the yield, don't create a new output.
+    if (indexLookup.count(value)) {
+      indices.push_back(indexLookup[value]);
+    } else {
+      // If the value is new, add it to the yield and to the types.
+      yieldValues.push_back(value);
       types.push_back(type);
       indices.push_back(yieldValues.size() - 1);
-    } else {
-      // If the value already exit the region don't create a new output.
-      for (auto [idx, yieldOperand] :
-           llvm::enumerate(yieldValues.getArrayRef())) {
-        if (yieldOperand == value) {
-          indices.push_back(idx);
-          break;
-        }
-      }
     }
   }
-  yieldValues.insert_range(newYieldedValues);
+
   WarpExecuteOnLane0Op newWarpOp = moveRegionToNewWarpOpAndReplaceReturns(
-      rewriter, warpOp, yieldValues.getArrayRef(), types);
+      rewriter, warpOp, yieldValues, types);
   rewriter.replaceOp(warpOp,
                      newWarpOp.getResults().take_front(warpOp.getNumResults()));
   return newWarpOp;

>From e49a6f18bdd5daf92ecab391051b12dd2edad6c5 Mon Sep 17 00:00:00 2001
From: Charitha Saumya <charitha.saumya.gusthinna.waduge at intel.com>
Date: Thu, 14 Aug 2025 19:31:48 +0000
Subject: [PATCH 2/2] add test

---
 .../Vector/vector-warp-distribute.mlir        | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/mlir/test/Dialect/Vector/vector-warp-distribute.mlir b/mlir/test/Dialect/Vector/vector-warp-distribute.mlir
index ae8fce786ee57..c3ce7e9ca7fda 100644
--- a/mlir/test/Dialect/Vector/vector-warp-distribute.mlir
+++ b/mlir/test/Dialect/Vector/vector-warp-distribute.mlir
@@ -1803,3 +1803,24 @@ func.func @warp_propagate_nd_write(%laneid: index, %dest: memref<4x1024xf32>) {
 //       CHECK-DIST-AND-PROP:   %[[IDS:.+]]:2 = affine.delinearize_index %{{.*}} into (4, 8) : index, index
 //       CHECK-DIST-AND-PROP:   %[[INNER_ID:.+]] = affine.apply #map()[%[[IDS]]#1]
 //       CHECK-DIST-AND-PROP:   vector.transfer_write %[[W]], %{{.*}}[%[[IDS]]#0, %[[INNER_ID]]] {{.*}} : vector<1x128xf32>
+
+// -----
+func.func @warp_propagate_duplicated_operands_in_yield(%laneid: index)  {
+  %r:3 = gpu.warp_execute_on_lane_0(%laneid)[32] -> (vector<1xf32>, vector<1xf32>, vector<1xf32>) {
+    %0 = "some_def"() : () -> (vector<32xf32>)
+    %1 = "some_other_def"() : () -> (vector<32xf32>)
+    %2 = math.exp %1 : vector<32xf32>
+    gpu.yield %2, %0, %0 : vector<32xf32>, vector<32xf32>, vector<32xf32>
+  }
+  "some_use"(%r#0) : (vector<1xf32>) -> ()
+  return
+}
+
+// CHECK-PROP-LABEL : func.func @warp_propagate_duplicated_operands_in_yield(
+// CHECK-PROP       :   %[[W:.*]] = gpu.warp_execute_on_lane_0(%{{.*}})[32] -> (vector<1xf32>) {
+// CHECK-PROP       :     %{{.*}} = "some_def"() : () -> vector<32xf32>
+// CHECK-PROP       :     %[[T3:.*]] = "some_other_def"() : () -> vector<32xf32>
+// CHECK-PROP       :     gpu.yield %[[T3]] : vector<32xf32>
+// CHECK-PROP       :   }
+// CHECK-PROP       :   %[T1:.*] = math.exp %[[W]] : vector<1xf32>
+// CHECK-PROP       :   "some_use"(%[[T1]]) : (vector<1xf32>) -> ()