[HW] Add reduction patterns to trim port list of top-level module (#7587

)

lib/Dialect/HW/HWReductions.cpp

@@ -135,6 +135,83 @@ struct HWConstantifier : public Reduction {
   std::string getName() const override { return "hw-constantifier"; }
 };
 
+/// Remove the first or last output of the top-level module depending on the
+/// 'Front' template parameter.
+template <bool Front>
+struct ModuleOutputPruner : public OpReduction<HWModuleOp> {
+  void beforeReduction(mlir::ModuleOp op) override {
+    useEmpty.clear();
+
+    SymbolTableCollection table;
+    SymbolUserMap users(table, op);
+    for (auto module : op.getOps<HWModuleOp>())
+      if (users.useEmpty(module))
+        useEmpty.insert(module);
+  }
+
+  uint64_t match(HWModuleOp op) override {
+    return op.getNumOutputPorts() != 0 && useEmpty.contains(op);
+  }
+
+  LogicalResult rewrite(HWModuleOp op) override {
+    Operation *terminator = op.getBody().front().getTerminator();
+    auto operands = terminator->getOperands();
+    ValueRange newOutputs = operands.drop_back();
+    unsigned portToErase = op.getNumOutputPorts() - 1;
+    if (Front) {
+      newOutputs = operands.drop_front();
+      portToErase = 0;
+    }
+
+    terminator->setOperands(newOutputs);
+    op.erasePorts({}, {portToErase});
+
+    return success();
+  }
+
+  std::string getName() const override {
+    return Front ? "hw-module-output-pruner-front"
+                 : "hw-module-output-pruner-back";
+  }
+
+  DenseSet<HWModuleOp> useEmpty;
+};
+
+/// Remove all input ports of the top-level module that have no users
+struct ModuleInputPruner : public OpReduction<HWModuleOp> {
+  void beforeReduction(mlir::ModuleOp op) override {
+    useEmpty.clear();
+
+    SymbolTableCollection table;
+    SymbolUserMap users(table, op);
+    for (auto module : op.getOps<HWModuleOp>())
+      if (users.useEmpty(module))
+        useEmpty.insert(module);
+  }
+
+  uint64_t match(HWModuleOp op) override { return useEmpty.contains(op); }
+
+  LogicalResult rewrite(HWModuleOp op) override {
+    SmallVector<unsigned> inputsToErase;
+    BitVector toErase(op.getNumPorts());
+    for (auto [i, arg] : llvm::enumerate(op.getBody().getArguments())) {
+      if (arg.use_empty()) {
+        toErase.set(i);
+        inputsToErase.push_back(i);
+      }
+    }
+
+    op.erasePorts(inputsToErase, {});
+    op.getBodyBlock()->eraseArguments(toErase);
+
+    return success();
+  }
+
+  std::string getName() const override { return "hw-module-input-pruner"; }
+
+  DenseSet<HWModuleOp> useEmpty;
+};
+
 //===----------------------------------------------------------------------===//
 // Reduction Registration
 //===----------------------------------------------------------------------===//
@@ -151,6 +228,9 @@ void HWReducePatternDialectInterface::populateReducePatterns(
   patterns.add<HWOperandForwarder<0>, 4>();
   patterns.add<HWOperandForwarder<1>, 3>();
   patterns.add<HWOperandForwarder<2>, 2>();
+  patterns.add<ModuleOutputPruner<true>, 2>();
+  patterns.add<ModuleOutputPruner<false>, 2>();
+  patterns.add<ModuleInputPruner, 2>();
 }
 
 void hw::registerReducePatternDialectInterface(

test/Dialect/Arc/Reduction/pattern-registration.mlir

@@ -6,19 +6,13 @@
 
 // RUN: circt-reduce %s --test /usr/bin/env --test-arg cat --list | FileCheck %s
 
-// CHECK: hw-
-// CHECK: hw-
-// CHECK: hw-
-// CHECK-NEXT: arc-strip-sv
-// CHECK-NEXT: cse
-// CHECK-NEXT: hw-
-// CHECK-NEXT: arc-dedup
-// CHECK-NEXT: canonicalize
-// CHECK-NEXT: hw-
-// CHECK-NEXT: arc-state-elimination
-// CHECK-NEXT: operation-pruner
-// CHECK-NEXT: arc-canonicalizer
-// CHECK-EMPTY:
+// CHECK-DAG: arc-strip-sv
+// CHECK-DAG: cse
+// CHECK-DAG: arc-dedup
+// CHECK-DAG: canonicalize
+// CHECK-DAG: arc-state-elimination
+// CHECK-DAG: operation-pruner
+// CHECK-DAG: arc-canonicalizer
 arc.define @DummyArc(%arg0: i32) -> i32 {
   arc.output %arg0 : i32
 }

test/Dialect/FIRRTL/Reduction/pattern-registration.mlir

@@ -7,41 +7,41 @@
 // RUN: circt-reduce %s --test /usr/bin/env --test-arg cat --list | FileCheck %s
 
 // CHECK:      firrtl-lower-chirrtl
-// CHECK-NEXT: firrtl-infer-widths
-// CHECK-NEXT: firrtl-infer-resets
-// CHECK-NEXT: firrtl-module-externalizer
-// CHECK-NEXT: instance-stubber
-// CHECK-NEXT: memory-stubber
-// CHECK-NEXT: eager-inliner
-// CHECK-NEXT: firrtl-lower-types
-// CHECK-NEXT: firrtl-expand-whens
-// CHECK-NEXT: firrtl-inliner
-// CHECK-NEXT: firrtl-imconstprop
-// CHECK-NEXT: firrtl-remove-unused-ports
-// CHECK-NEXT: node-symbol-remover
-// CHECK-NEXT: connect-forwarder
-// CHECK-NEXT: connect-invalidator
-// CHECK-NEXT: firrtl-constantifier
-// CHECK-NEXT: firrtl-operand0-forwarder
-// CHECK-NEXT: firrtl-operand1-forwarder
-// CHECK-NEXT: firrtl-operand2-forwarder
-// CHECK-NEXT: detach-subaccesses
-// CHECK-NEXT: hw-module-externalizer
-// CHECK-NEXT: annotation-remover
-// CHECK-NEXT: hw-constantifier
-// CHECK-NEXT: root-port-pruner
-// CHECK-NEXT: hw-operand0-forwarder
-// CHECK-NEXT: extmodule-instance-remover
-// CHECK-NEXT: cse
-// CHECK-NEXT: hw-operand1-forwarder
-// CHECK-NEXT: connect-source-operand-0-forwarder
-// CHECK-NEXT: canonicalize
-// CHECK-NEXT: hw-operand2-forwarder
-// CHECK-NEXT: connect-source-operand-1-forwarder
-// CHECK-NEXT: operation-pruner
-// CHECK-NEXT: connect-source-operand-2-forwarder
-// CHECK-NEXT: module-internal-name-sanitizer
-// CHECK-NEXT: module-name-sanitizer
+// CHECK-DAG: firrtl-infer-widths
+// CHECK-DAG: firrtl-infer-resets
+// CHECK-DAG: firrtl-module-externalizer
+// CHECK-DAG: instance-stubber
+// CHECK-DAG: memory-stubber
+// CHECK-DAG: eager-inliner
+// CHECK-DAG: firrtl-lower-types
+// CHECK-DAG: firrtl-expand-whens
+// CHECK-DAG: firrtl-inliner
+// CHECK-DAG: firrtl-imconstprop
+// CHECK-DAG: firrtl-remove-unused-ports
+// CHECK-DAG: node-symbol-remover
+// CHECK-DAG: connect-forwarder
+// CHECK-DAG: connect-invalidator
+// CHECK-DAG: firrtl-constantifier
+// CHECK-DAG: firrtl-operand0-forwarder
+// CHECK-DAG: firrtl-operand1-forwarder
+// CHECK-DAG: firrtl-operand2-forwarder
+// CHECK-DAG: detach-subaccesses
+// CHECK-DAG: hw-module-externalizer
+// CHECK-DAG: annotation-remover
+// CHECK-DAG: hw-constantifier
+// CHECK-DAG: root-port-pruner
+// CHECK-DAG: hw-operand0-forwarder
+// CHECK-DAG: extmodule-instance-remover
+// CHECK-DAG: cse
+// CHECK-DAG: hw-operand1-forwarder
+// CHECK-DAG: connect-source-operand-0-forwarder
+// CHECK-DAG: canonicalize
+// CHECK-DAG: hw-operand2-forwarder
+// CHECK-DAG: connect-source-operand-1-forwarder
+// CHECK-DAG: operation-pruner
+// CHECK-DAG: connect-source-operand-2-forwarder
+// CHECK-DAG: module-internal-name-sanitizer
+// CHECK-DAG: module-name-sanitizer
 // CHECK-EMPTY:
 firrtl.circuit "Foo" {
   firrtl.module @Foo() {}

test/Dialect/HW/Reduction/hw-module-input-pruner.mlir

@@ -0,0 +1,9 @@
+// UNSUPPORTED: system-windows
+//   See https://github.com/llvm/circt/issues/4129
+// RUN: circt-reduce %s --test /usr/bin/env --test-arg grep --test-arg -q --test-arg "hw.output %arg" --keep-best=0 --include hw-module-input-pruner | FileCheck %s
+
+// CHECK-LABEL: hw.module @Foo(in %arg0 : i32, out out0 : i32)
+hw.module @Foo(in %arg0 : i32, in %arg1 : i32, in %arg2 : i32, out out0 : i32) {
+  // CHECK-NEXT: hw.output %arg0 : i32
+  hw.output %arg0 : i32
+}

test/Dialect/HW/Reduction/hw-module-output-pruner.mlir

@@ -0,0 +1,12 @@
+// UNSUPPORTED: system-windows
+//   See https://github.com/llvm/circt/issues/4129
+// RUN: circt-reduce %s --test /usr/bin/env --test-arg grep --test-arg -q --test-arg "hw.output %arg" --keep-best=0 --include hw-module-output-pruner-back | FileCheck %s --check-prefix=CHECK-BACK
+// RUN: circt-reduce %s --test /usr/bin/env --test-arg grep --test-arg -q --test-arg "hw.output %arg" --keep-best=0 --include hw-module-output-pruner-front | FileCheck %s --check-prefix=CHECK-FRONT
+
+// CHECK-FRONT-LABEL: hw.module @Foo(in %arg0 : i32, in %arg1 : i32, in %arg2 : i32, out out2 : i32)
+// CHECK-BACK-LABEL: hw.module @Foo(in %arg0 : i32, in %arg1 : i32, in %arg2 : i32, out out0 : i32)
+hw.module @Foo(in %arg0 : i32, in %arg1 : i32, in %arg2 : i32, out out0 : i32, out out1 : i32, out out2 : i32) {
+  // CHECK-FRONT-NEXT: hw.output %arg2 : i32
+  // CHECK-BACK-NEXT: hw.output %arg0 : i32
+  hw.output %arg0, %arg1, %arg2 : i32, i32, i32
+}

test/Dialect/HW/Reduction/pattern-registration.mlir

@@ -6,15 +6,17 @@
 
 // RUN: circt-reduce %s --test /usr/bin/env --test-arg cat --list | FileCheck %s
 
-// CHECK:      hw-module-externalizer
-// CHECK-NEXT: hw-constantifier
-// CHECK-NEXT: hw-operand0-forwarder
-// CHECK-NEXT: cse
-// CHECK-NEXT: hw-operand1-forwarder
-// CHECK-NEXT: canonicalize
-// CHECK-NEXT: hw-operand2-forwarder
-// CHECK-NEXT: operation-pruner
-// CHECK-EMPTY:
+// CHECK-DAG: hw-module-externalizer
+// CHECK-DAG: hw-constantifier
+// CHECK-DAG: hw-operand0-forwarder
+// CHECK-DAG: cse
+// CHECK-DAG: hw-operand1-forwarder
+// CHECK-DAG: canonicalize
+// CHECK-DAG: hw-operand2-forwarder
+// CHECK-DAG: hw-module-output-pruner-front
+// CHECK-DAG: hw-module-output-pruner-back
+// CHECK-DAG: hw-module-input-pruner
+// CHECK-DAG: operation-pruner
 hw.module @Foo(in %in : i1, out out : i1) {
   hw.output %in : i1
 }