[Seq] Fix the canonicalization of seq registers with a clock type (#6274

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llvm · Oct 10, 2023 · 225e26e · 225e26e
1 parent 0d7cd67
commit 225e26e
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Showing 2 changed files with 17 additions and 3 deletions.
diff --git a/lib/Dialect/Seq/SeqOps.cpp b/lib/Dialect/Seq/SeqOps.cpp
@@ -526,9 +526,15 @@ LogicalResult FirRegOp::canonicalize(FirRegOp op, PatternRewriter &rewriter) {
       // If the register has a reset value, we can replace it with that.
       rewriter.replaceOp(op, resetValue);
     } else {
-      auto constant = rewriter.create<hw::ConstantOp>(
-          op.getLoc(), APInt::getZero(hw::getBitWidth(op.getType())));
-      rewriter.replaceOpWithNewOp<hw::BitcastOp>(op, op.getType(), constant);
+      if (op.getType().isa<seq::ClockType>()) {
+        rewriter.replaceOpWithNewOp<seq::ConstClockOp>(
+            op,
+            seq::ClockConstAttr::get(rewriter.getContext(), ClockConst::Low));
+      } else {
+        auto constant = rewriter.create<hw::ConstantOp>(
+            op.getLoc(), APInt::getZero(hw::getBitWidth(op.getType())));
+        rewriter.replaceOpWithNewOp<hw::BitcastOp>(op, op.getType(), constant);
+      }
     }
     return success();
   }

diff --git a/test/Dialect/Seq/canonicalization.mlir b/test/Dialect/Seq/canonicalization.mlir
@@ -230,4 +230,12 @@ hw.module @const_clock(out clock_true : !seq.clock, out clock_false : !seq.clock
 
   // CHECK: hw.output [[CLOCK_FALSE]], [[CLOCK_TRUE]]
   hw.output %clock_false, %clock_true : !seq.clock, !seq.clock
+}
+
+// CHECK-LABEL: @const_clock_reg
+hw.module @const_clock_reg(in %clock : !seq.clock, out r_data : !seq.clock) {
+  // CHECK: seq.const_clock low
+  %0 = seq.const_clock  low
+  %1 = seq.firreg %1 clock %0 : !seq.clock
+  hw.output %1 : !seq.clock
 }