From dd7b402d96ebfdf9db5567922a5dce285e99dfc1 Mon Sep 17 00:00:00 2001
From: Liam Jay <145520385+liamslj13@users.noreply.github.com>
Date: Fri, 11 Jul 2025 06:50:42 +0900
Subject: [PATCH] [MooreToCore] Lower moore.powu to math.ipowi (#8654)

Change PowUOpConversion to call into the MLIR math dialect for unsigned
integer exponentiation.
---
 lib/Conversion/MooreToCore/MooreToCore.cpp | 29 +++++++---------------
 test/Conversion/MooreToCore/basic.mlir     |  8 +++---
 2 files changed, 14 insertions(+), 23 deletions(-)

diff --git a/lib/Conversion/MooreToCore/MooreToCore.cpp b/lib/Conversion/MooreToCore/MooreToCore.cpp
index 6efee48444..350a91587a 100644
--- a/lib/Conversion/MooreToCore/MooreToCore.cpp
+++ b/lib/Conversion/MooreToCore/MooreToCore.cpp
@@ -1325,29 +1325,18 @@ struct PowUOpConversion : public OpConversionPattern<PowUOp> {
                   ConversionPatternRewriter &rewriter) const override {
     Type resultType = typeConverter->convertType(op.getResult().getType());
 
-    Location loc = op.getLoc();
-    auto intType = cast<IntType>(op.getRhs().getType());
+    Location loc = op->getLoc();
 
-    // transform a ** b into scf.for 0 to b step 1 { init *= a }, init = 1
-    Type integerType = rewriter.getIntegerType(intType.getWidth());
-    Value lowerBound = rewriter.create<hw::ConstantOp>(loc, integerType, 0);
-    Value upperBound =
-        rewriter.create<ConversionOp>(loc, integerType, op.getRhs());
-    Value step = rewriter.create<hw::ConstantOp>(loc, integerType, 1);
+    Value zeroVal = rewriter.create<hw::ConstantOp>(loc, APInt(1, 0));
+    // zero extend both LHS & RHS to ensure the unsigned integers are
+    // interpreted correctly when calculating power
+    auto lhs = rewriter.create<comb::ConcatOp>(loc, zeroVal, adaptor.getLhs());
+    auto rhs = rewriter.create<comb::ConcatOp>(loc, zeroVal, adaptor.getRhs());
 
-    Value initVal = rewriter.create<hw::ConstantOp>(loc, resultType, 1);
-    Value lhsVal = rewriter.create<ConversionOp>(loc, resultType, op.getLhs());
-
-    auto forOp = rewriter.create<scf::ForOp>(
-        loc, lowerBound, upperBound, step, ValueRange(initVal),
-        [&](OpBuilder &builder, Location loc, Value i, ValueRange iterArgs) {
-          Value loopVar = iterArgs.front();
-          Value mul = rewriter.create<comb::MulOp>(loc, lhsVal, loopVar);
-          rewriter.create<scf::YieldOp>(loc, ValueRange(mul));
-        });
-
-    rewriter.replaceOp(op, forOp.getResult(0));
+    // lower the exponentiation via MLIR's math dialect
+    auto pow = rewriter.create<mlir::math::IPowIOp>(loc, lhs, rhs);
 
+    rewriter.replaceOpWithNewOp<comb::ExtractOp>(op, resultType, pow, 0);
     return success();
   }
 };
diff --git a/test/Conversion/MooreToCore/basic.mlir b/test/Conversion/MooreToCore/basic.mlir
index 6c5f22691f..c6df3d449e 100644
--- a/test/Conversion/MooreToCore/basic.mlir
+++ b/test/Conversion/MooreToCore/basic.mlir
@@ -1111,9 +1111,11 @@ func.func @Conversions(%arg0: !moore.i16, %arg1: !moore.l16) {
 
 // CHECK-LABEL: func.func @PowUOp
 func.func @PowUOp(%arg0: !moore.l32, %arg1: !moore.l32) {
-  // CHECK: %{{.*}} = scf.for %{{.*}} = %{{.*}} to %arg1 step %{{.*}} iter_args([[VAR:%.+]] = %{{.*}}) -> (i32)  : i32 {
-  // CHECK: [[MUL:%.+]] = comb.mul %arg0, [[VAR]] : i32
-  // CHECK: scf.yield [[MUL]] : i32
+  // CHECK: %[[ZEROVAL:.*]] = hw.constant false
+  // CHECK: %[[CONCATA:.*]] = comb.concat %[[ZEROVAL]], %arg0 : i1, i32
+  // CHECK: %[[CONCATB:.*]] = comb.concat %[[ZEROVAL]], %arg1 : i1, i32
+  // CHECK: %[[RES:.*]] = math.ipowi %[[CONCATA]], %[[CONCATB]] : i33
+  // CHECK: comb.extract %[[RES]] from 0 : (i33) -> i32
   %0 = moore.powu %arg0, %arg1 : l32
   return
 }