Disable Attention V operand transposition. (iree-org#19810)

This impacts the ability to horizontally fuse the matmuls that feed into
`Q-K-V` transpose. The improvements seen with the change might have been
due to reduction in copy overheads, which are no more an issue.

Signed-off-by: MaheshRavishankar <[email protected]>

Author: MaheshRavishankar

compiler/src/iree/compiler/GlobalOptimization/Passes.cpp

@@ -34,6 +34,10 @@ static llvm::cl::opt<bool> clEnableTransposePropagation(
     llvm::cl::desc(
         "Enables propagation of transpose ops to improve fusion chances."),
     llvm::cl::init(true));
+static llvm::cl::opt<bool> clEnableAttentionVTranspose(
+    "iree-global-opt-enable-attention-v-transpose",
+    llvm::cl::desc("Enables transposition of v operand of attention ops,"),
+    llvm::cl::init(true));
 
 // TODO(hanchung): Remove the flag. We don't want to do early materialization by
 // default. Because it won't work for heterogeneous computing. This is not the
@@ -157,8 +161,11 @@ void buildGlobalOptimizationPassPipeline(
       .addPredicatedPass(
           clEnableTransposePropagation,
           [&]() {
-            return createPropagateLinalgTransposePass(
-                transformOptions.options.aggressiveTransposePropagation);
+            PropagateLinalgTransposePassOptions options;
+            options.enableAggressivePropagation =
+                transformOptions.options.aggressiveTransposePropagation;
+            options.enableAttentionVTranspose = clEnableAttentionVTranspose;
+            return createPropagateLinalgTransposePass(options);
           })
       .addPass(IREE::Flow::createCanonicalizerPass)
       .addPass(mlir::createCSEPass);

compiler/src/iree/compiler/GlobalOptimization/Passes.td

@@ -115,6 +115,8 @@ def PropagateLinalgTransposePass :
            "Flag used for lit-testing sinking patterns only. Not for general usage">,
     Option<"testBubblingOnly", "test-bubbling-only", "bool", /*default=*/"false",
            "Flag used for lit-testing bubbling patterns only. Not for general usage">,
+    Option<"enableAttentionVTranspose", "enable-attention-v-transpose", "bool",
+            /*default=*/"true", "Enable transposition of attention v operand">,
   ];
 }
 

compiler/src/iree/compiler/GlobalOptimization/PropagateLinalgTranspose.cpp

@@ -1092,15 +1092,19 @@ void PropagateLinalgTransposePass::runOnOperation() {
     linalg::populateFoldReshapeOpsByExpansionPatterns(bubblingPatterns,
                                                       reshapePropagationFn);
     linalg::FillOp::getCanonicalizationPatterns(bubblingPatterns, context);
-    linalg::ControlFusionFn bubbleTransposeControlFn =
-        [](OpOperand *fusedOperand) {
-          Operation *producer = fusedOperand->get().getDefiningOp();
-          Operation *consumer = fusedOperand->getOwner();
 
-          return IREE::Flow::isNonNullAndOutsideDispatch({producer, consumer});
-        };
-    IREE::LinalgExt::populateBubbleTransposeFromLinalgExtOps(
-        bubblingPatterns, bubbleTransposeControlFn);
+    if (enableAttentionVTranspose) {
+      linalg::ControlFusionFn bubbleTransposeControlFn =
+          [](OpOperand *fusedOperand) {
+            Operation *producer = fusedOperand->get().getDefiningOp();
+            Operation *consumer = fusedOperand->getOwner();
+
+            return IREE::Flow::isNonNullAndOutsideDispatch(
+                {producer, consumer});
+          };
+      IREE::LinalgExt::populateBubbleTransposeFromLinalgExtOps(
+          bubblingPatterns, bubbleTransposeControlFn);
+    }
     bubblingPatterns.insert<FuseTransposeWithProducerLinalgOp>(
         context, enableAggressivePropagation);
     bubblingPatterns.insert<BubbleTransposeThroughCollapseShape>(context);