Comb Interval Range Analysis and Comb Opt Narrowing pass

include/circt/Dialect/Comb/Comb.td

@@ -15,6 +15,7 @@
 
 include "mlir/IR/OpBase.td"
 include "mlir/Interfaces/SideEffectInterfaces.td"
+include "mlir/Interfaces/InferIntRangeInterface.td"
 include "mlir/IR/OpAsmInterface.td"
 include "mlir/IR/SymbolInterfaces.td"
 

include/circt/Dialect/Comb/CombOps.h

@@ -20,6 +20,7 @@
 #include "mlir/IR/BuiltinOps.h"
 #include "mlir/IR/OpImplementation.h"
 #include "mlir/Interfaces/FunctionInterfaces.h"
+#include "mlir/Interfaces/InferIntRangeInterface.h"
 #include "mlir/Interfaces/InferTypeOpInterface.h"
 #include "mlir/Interfaces/SideEffectInterfaces.h"
 

include/circt/Dialect/Comb/CombPasses.h

@@ -18,6 +18,10 @@
 #include <memory>
 #include <optional>
 
+namespace mlir {
+class DataFlowSolver;
+}
+
 namespace circt {
 namespace comb {
 
@@ -26,6 +30,10 @@ namespace comb {
 #define GEN_PASS_REGISTRATION
 #include "circt/Dialect/Comb/Passes.h.inc"
 
+/// Add patterns for int range based narrowing.
+void populateCombNarrowingPatterns(mlir::RewritePatternSet &patterns,
+                                   mlir::DataFlowSolver &solver);
+
 } // namespace comb
 } // namespace circt
 

include/circt/Dialect/Comb/Combinational.td

@@ -15,6 +15,7 @@
 //===----------------------------------------------------------------------===//
 
 include "mlir/Interfaces/InferTypeOpInterface.td"
+include "mlir/Interfaces/InferIntRangeInterface.td"
 include "mlir/IR/EnumAttr.td"
 
 // Base class for binary operators.
@@ -30,7 +31,9 @@ class BinOp<string mnemonic, list<Trait> traits = []> :
 // Binary operator with uniform input/result types.
 class UTBinOp<string mnemonic, list<Trait> traits = []> :
       BinOp<mnemonic,
-               traits # [SameTypeOperands, SameOperandsAndResultType]> {
+               traits # [SameTypeOperands, SameOperandsAndResultType, 
+                DeclareOpInterfaceMethods<InferIntRangeInterface, 
+                                          ["inferResultRanges"]>]> {
   let assemblyFormat = "(`bin` $twoState^)? $lhs `,` $rhs attr-dict `:` qualified(type($result))";
 }
 
@@ -42,8 +45,10 @@ class VariadicOp<string mnemonic, list<Trait> traits = []> :
 }
 
 class UTVariadicOp<string mnemonic, list<Trait> traits = []> :
-      VariadicOp<mnemonic,
-                    traits # [SameTypeOperands, SameOperandsAndResultType]> {
+      VariadicOp<mnemonic, 
+                  traits # [SameTypeOperands, SameOperandsAndResultType, 
+                   DeclareOpInterfaceMethods<InferIntRangeInterface, 
+                                             ["inferResultRanges"]>]> {
 
   let hasCanonicalizeMethod = true;
   let hasFolder = true;
@@ -76,7 +81,7 @@ let hasFolder = true in {
 }
 
 def AndOp : UTVariadicOp<"and", [Commutative]>;
-def OrOp  : UTVariadicOp<"or", [Commutative]>;
+def OrOp  : UTVariadicOp<"or",  [Commutative]>;
 def XorOp : UTVariadicOp<"xor", [Commutative]> {
   let extraClassDeclaration = [{
     /// Return true if this is a two operand xor with an all ones constant as
@@ -114,7 +119,10 @@ def ICmpPredicate : I64EnumAttr<
      ICmpPredicateUGT, ICmpPredicateUGE, ICmpPredicateCEQ, ICmpPredicateCNE,
      ICmpPredicateWEQ, ICmpPredicateWNE]>;
 
-def ICmpOp : CombOp<"icmp", [Pure, SameTypeOperands]> {
+def ICmpOp : CombOp<"icmp", 
+  [Pure, 
+   SameTypeOperands, 
+   DeclareOpInterfaceMethods<InferIntRangeInterface, ["inferResultRanges"]>]> {
   let summary = "Compare two integer values";
   let description = [{
     This operation compares two integers using a predicate.  If the predicate is
@@ -178,7 +186,9 @@ def ParityOp : UnaryI1ReductionOp<"parity">;
 //===----------------------------------------------------------------------===//
 
 // Extract a range of bits from the specified input.
-def ExtractOp : CombOp<"extract", [Pure]> {
+def ExtractOp : CombOp<"extract", 
+  [Pure, 
+   DeclareOpInterfaceMethods<InferIntRangeInterface, ["inferResultRanges"]>]> {
   let summary = "Extract a range of bits into a smaller value, lowBit "
                 "specifies the lowest bit included.";
 
@@ -203,7 +213,9 @@ def ExtractOp : CombOp<"extract", [Pure]> {
 //===----------------------------------------------------------------------===//
 // Other Operations
 //===----------------------------------------------------------------------===//
-def ConcatOp : CombOp<"concat", [InferTypeOpInterface, Pure]> {
+def ConcatOp : CombOp<"concat", 
+  [InferTypeOpInterface, Pure, 
+   DeclareOpInterfaceMethods<InferIntRangeInterface, ["inferResultRanges"]>]> {
   let summary = "Concatenate a variadic list of operands together.";
   let description = [{
     See the comb rationale document for details on operand ordering.
@@ -237,7 +249,9 @@ def ConcatOp : CombOp<"concat", [InferTypeOpInterface, Pure]> {
   }];
 }
 
-def ReplicateOp : CombOp<"replicate", [Pure]> {
+def ReplicateOp : CombOp<"replicate", 
+  [Pure, 
+   DeclareOpInterfaceMethods<InferIntRangeInterface, ["inferResultRanges"]>]> {
   let summary = "Concatenate the operand a constant number of times";
 
   let arguments = (ins HWIntegerType:$input);
@@ -267,8 +281,10 @@ def ReplicateOp : CombOp<"replicate", [Pure]> {
 }
 
 // Select one of two values based on a condition.
-def MuxOp : CombOp<"mux",
- [Pure, AllTypesMatch<["trueValue", "falseValue", "result"]>]> {
+def MuxOp : CombOp<"mux", 
+  [Pure,   AllTypesMatch<["trueValue", "falseValue", "result"]>,
+   DeclareOpInterfaceMethods<InferIntRangeInterface, 
+                            ["inferResultRangesFromOptional"]>]> {
   let summary = "Return one or the other operand depending on a selector bit";
   let description = [{
     ```

include/circt/Dialect/Comb/Passes.td

@@ -22,4 +22,16 @@ def LowerComb : Pass<"lower-comb"> {
   }];
 }
 
+def CombIntRangeNarrowing : Pass<"comb-int-range-narrowing"> {
+  let summary = "Reduce comb op bitwidth based on integer range analysis.";
+  let description = [{
+    Compute a basic value range analysis, by propagating integer intervals 
+    through the domain. The analysis is limited by a lack of sign-extension 
+    operator in the comb dialect, leading to an over-approximation. 
+    Particularly for signed arithmetic, a single interval is often an 
+    over-approximation, a more precise analysis would require a union of 
+    intervals.
+  }];
+}
+
 #endif // CIRCT_DIALECT_COMB_PASSES_TD

include/circt/Dialect/HW/HWMiscOps.td

@@ -19,11 +19,14 @@ include "circt/Dialect/HW/HWOpInterfaces.td"
 include "circt/Dialect/HW/HWTypes.td"
 include "mlir/IR/OpAsmInterface.td"
 include "mlir/Interfaces/InferTypeOpInterface.td"
+include "mlir/Interfaces/InferIntRangeInterface.td"
 include "mlir/Interfaces/SideEffectInterfaces.td"
 
 def ConstantOp
  : HWOp<"constant", [Pure, ConstantLike, FirstAttrDerivedResultType,
-         DeclareOpInterfaceMethods<OpAsmOpInterface, ["getAsmResultNames"]>]> {
+         DeclareOpInterfaceMethods<OpAsmOpInterface, ["getAsmResultNames"]>,
+         DeclareOpInterfaceMethods<InferIntRangeInterface, 
+                                   ["inferResultRanges"]>]> {
   let summary = "Produce a constant value";
   let description = [{
     The constant operation produces a constant value of standard integer type

include/circt/Dialect/HW/HWOps.h

@@ -26,6 +26,7 @@
 #include "mlir/IR/SymbolTable.h"
 #include "mlir/Interfaces/ControlFlowInterfaces.h"
 #include "mlir/Interfaces/FunctionInterfaces.h"
+#include "mlir/Interfaces/InferIntRangeInterface.h"
 #include "mlir/Interfaces/InferTypeOpInterface.h"
 #include "mlir/Interfaces/SideEffectInterfaces.h"
 #include "llvm/ADT/StringExtras.h"

lib/Analysis/TestPasses.cpp

@@ -18,6 +18,8 @@
 #include "circt/Dialect/FIRRTL/FIRRTLInstanceGraph.h"
 #include "circt/Dialect/HW/HWInstanceGraph.h"
 #include "circt/Scheduling/Problems.h"
+#include "mlir/Analysis/DataFlow/DeadCodeAnalysis.h"
+#include "mlir/Analysis/DataFlow/IntegerRangeAnalysis.h"
 #include "mlir/Dialect/Affine/IR/AffineMemoryOpInterfaces.h"
 #include "mlir/Dialect/Affine/IR/AffineOps.h"
 #include "mlir/Dialect/Func/IR/FuncOps.h"
@@ -29,6 +31,7 @@
 
 using namespace mlir;
 using namespace mlir::affine;
+using namespace mlir::dataflow;
 using namespace circt;
 using namespace circt::analysis;
 using namespace circt::scheduling;
@@ -263,6 +266,69 @@ void FIRRTLInstanceInfoPass::runOnOperation() {
     printModuleInfo(op, iInfo);
 }
 
+//===----------------------------------------------------------------------===//
+// Comb IntRange Analysis
+//===----------------------------------------------------------------------===//
+
+namespace {
+struct TestCombIntegerRangeAnalysisPass
+    : public PassWrapper<TestCombIntegerRangeAnalysisPass,
+                         OperationPass<mlir::ModuleOp>> {
+  MLIR_DEFINE_EXPLICIT_INTERNAL_INLINE_TYPE_ID(TestCombIntegerRangeAnalysisPass)
+
+  void runOnOperation() override;
+  StringRef getArgument() const override {
+    return "test-comb-int-range-analysis";
+  }
+  StringRef getDescription() const override {
+    return "Perform integer range analysis on comb dialect and set results as "
+           "attributes.";
+  }
+};
+} // namespace
+
+void TestCombIntegerRangeAnalysisPass::runOnOperation() {
+  Operation *op = getOperation();
+  MLIRContext *ctx = op->getContext();
+  DataFlowSolver solver;
+  solver.load<DeadCodeAnalysis>();
+  solver.load<IntegerRangeAnalysis>();
+  if (failed(solver.initializeAndRun(op)))
+    return signalPassFailure();
+
+  // Append the integer range analysis as an operation attribute.
+  op->walk([&](Operation *op) {
+    for (auto value : op->getResults()) {
+      if (auto *range = solver.lookupState<IntegerValueRangeLattice>(value)) {
+        // All analyzed comb operations should return a single result.
+        assert(op->getResults().size() == 1 &&
+               "Expected a single result for the operation analysis");
+        assert(!range->getValue().isUninitialized() &&
+               "Expected a valid range for the value");
+        auto interval = range->getValue().getValue();
+        auto smax = interval.smax();
+        auto smaxAttr =
+            IntegerAttr::get(IntegerType::get(ctx, smax.getBitWidth()), smax);
+        op->setAttr("smax", smaxAttr);
+        auto smin = interval.smin();
+        auto sminAttr =
+            IntegerAttr::get(IntegerType::get(ctx, smin.getBitWidth()), smin);
+        op->setAttr("smin", sminAttr);
+        auto umax = interval.umax();
+        auto umaxAttr = IntegerAttr::get(
+            IntegerType::get(ctx, umax.getBitWidth(), IntegerType::Unsigned),
+            umax);
+        op->setAttr("umax", umaxAttr);
+        auto umin = interval.umin();
+        auto uminAttr = IntegerAttr::get(
+            IntegerType::get(ctx, umin.getBitWidth(), IntegerType::Unsigned),
+            umin);
+        op->setAttr("umin", uminAttr);
+      }
+    }
+  });
+}
+
 //===----------------------------------------------------------------------===//
 // Pass registration
 //===----------------------------------------------------------------------===//
@@ -285,6 +351,9 @@ void registerAnalysisTestPasses() {
   registerPass([]() -> std::unique_ptr<Pass> {
     return std::make_unique<FIRRTLInstanceInfoPass>();
   });
+  registerPass([]() -> std::unique_ptr<Pass> {
+    return std::make_unique<TestCombIntegerRangeAnalysisPass>();
+  });
 }
 } // namespace test
 } // namespace circt

lib/Dialect/Comb/CMakeLists.txt

@@ -3,6 +3,7 @@ add_circt_dialect_library(CIRCTComb
   CombOps.cpp
   CombAnalysis.cpp
   CombDialect.cpp
+  InferIntRangeInterfaceImpls.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${CIRCT_MAIN_INCLUDE_DIR}/circt/Dialect/Comb
@@ -19,6 +20,7 @@ add_circt_dialect_library(CIRCTComb
   CIRCTHW
   MLIRIR
   MLIRInferTypeOpInterface
+  MLIRInferIntRangeInterface
    )
 
 add_dependencies(circt-headers MLIRCombIncGen MLIRCombEnumsIncGen)