[PATCH] D91501: [VPlan] VPTransformState::get() can always return lane 0 for uniforms.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: Ayal, gilr, rengolin.
Herald added subscribers: psnobl, rogfer01, bollu, hiraditya.
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When requesting a scalar value for a uniform VPDef, we can always return
lane 0. This can avoid unnecessary inserting some unncessary instructions
to duplicate the uniform value across lanes.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D91501

Files:
  llvm/lib/Transforms/Vectorize/VPlan.cpp
  llvm/lib/Transforms/Vectorize/VPlan.h


Index: llvm/lib/Transforms/Vectorize/VPlan.h
===================================================================
--- llvm/lib/Transforms/Vectorize/VPlan.h
+++ llvm/lib/Transforms/Vectorize/VPlan.h
@@ -286,25 +286,7 @@
   }
 
   /// Get the generated Value for a given VPValue and given Part and Lane.
-  Value *get(VPValue *Def, const VPIteration &Instance) {
-    // If the Def is managed directly by VPTransformState, extract the lane from
-    // the relevant part. Note that currently only VPInstructions and external
-    // defs are managed by VPTransformState. Other Defs are still created by ILV
-    // and managed in its ValueMap. For those this method currently just
-    // delegates the call to ILV below.
-    if (Data.PerPartOutput.count(Def)) {
-      auto *VecPart = Data.PerPartOutput[Def][Instance.Part];
-      if (!VecPart->getType()->isVectorTy()) {
-        assert(Instance.Lane == 0 && "cannot get lane > 0 for scalar");
-        return VecPart;
-      }
-      // TODO: Cache created scalar values.
-      return Builder.CreateExtractElement(VecPart,
-                                          Builder.getInt32(Instance.Lane));
-    }
-
-    return Callback.getOrCreateScalarValue(VPValue2Value[Def], Instance);
-  }
+  Value *get(VPValue *Def, VPIteration Instance);
 
   /// Set the generated Value for a given VPValue and a given Part.
   void set(VPValue *Def, Value *V, unsigned Part) {
Index: llvm/lib/Transforms/Vectorize/VPlan.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/VPlan.cpp
+++ llvm/lib/Transforms/Vectorize/VPlan.cpp
@@ -244,6 +244,31 @@
   return It;
 }
 
+Value *VPTransformState::get(VPValue *Def, VPIteration Instance) {
+  // For uniform definitions, all lanes produce the same value, so we can always
+  // return the first lane.
+  if (auto *ReplicateR = dyn_cast<VPReplicateRecipe>(Def))
+    if (ReplicateR->isUniform())
+      Instance.Lane = 0;
+  // If the Def is managed directly by VPTransformState, extract the lane from
+  // the relevant part. Note that currently only VPInstructions and external
+  // defs are managed by VPTransformState. Other Defs are still created by ILV
+  // and managed in its ValueMap. For those this method currently just
+  // delegates the call to ILV below.
+  if (Data.PerPartOutput.count(Def)) {
+    auto *VecPart = Data.PerPartOutput[Def][Instance.Part];
+    if (!VecPart->getType()->isVectorTy()) {
+      assert(Instance.Lane == 0 && "cannot get lane > 0 for scalar");
+      return VecPart;
+    }
+    // TODO: Cache created scalar values.
+    return Builder.CreateExtractElement(VecPart,
+                                        Builder.getInt32(Instance.Lane));
+  }
+
+  return Callback.getOrCreateScalarValue(VPValue2Value[Def], Instance);
+}
+
 BasicBlock *
 VPBasicBlock::createEmptyBasicBlock(VPTransformState::CFGState &CFG) {
   // BB stands for IR BasicBlocks. VPBB stands for VPlan VPBasicBlocks.


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