[MSFT] Remove ChannelOp

This was unused. Fixes #6660.

include/circt/Dialect/MSFT/MSFTConstructs.td

@@ -45,30 +45,6 @@ def PEOutputOp: MSFTOp<"pe.output", [Terminator]> {
   let assemblyFormat = "$output attr-dict `:` type($output)";
 }
 
-def ChannelOp: MSFTOp<"constructs.channel",
-    [Pure, Symbol,
-     AllTypesMatch<["input", "output"]>]> {
-
-  let summary = "A pipeline-able connection";
-  let description = [{
-    A logical, feed-forward connection between a producer and consumer. Can be
-    pipelined with a number of stages (cycle delay) on a per-instance basis.
-    `defaultStages` is used when `stages` isn't specified by a
-    `DynamicInstance`. Non-resettable, for now.
-
-    Per-instance specification is not yet supported, so the default pipelining
-    is always used.
-  }];
-
-  let arguments = (ins AnyType:$input, ClockType:$clk, StrAttr:$sym_name,
-                       UI64Attr:$defaultStages);
-  let results = (outs AnyType:$output);
-
-  let assemblyFormat = [{
-    $input $clk $sym_name `(` $defaultStages `)` attr-dict `:` type($input)
-  }];
-}
-
 // Linear, pipelineable datapath.
 def LinearOp : MSFTOp<"hlc.linear", [
     SingleBlockImplicitTerminator<"OutputOp">

lib/Dialect/MSFT/Transforms/MSFTLowerConstructs.cpp

@@ -157,35 +157,6 @@ public:
 };
 } // anonymous namespace
 
-namespace {
-/// Lower MSFT's ChannelOp to a set of registers.
-struct ChannelOpLowering : public OpConversionPattern<ChannelOp> {
-public:
-  ChannelOpLowering(MLIRContext *ctxt, LowerConstructsPass &pass)
-      : OpConversionPattern(ctxt), pass(pass) {}
-
-  LogicalResult
-  matchAndRewrite(ChannelOp chan, OpAdaptor adaptor,
-                  ConversionPatternRewriter &rewriter) const final {
-    Location loc = chan.getLoc();
-    Operation *mod = chan->getParentOfType<hw::HWModuleLike>();
-    assert(mod && "ChannelOp must be contained by module");
-    Namespace &ns = pass.getNamespaceFor(mod);
-    Value clk = chan.getClk();
-    Value v = chan.getInput();
-    for (uint64_t stageNum = 0, e = chan.getDefaultStages(); stageNum < e;
-         ++stageNum)
-      v = rewriter.create<seq::CompRegOp>(loc, v, clk,
-                                          ns.newName(chan.getSymName()));
-    rewriter.replaceOp(chan, {v});
-    return success();
-  }
-
-protected:
-  LowerConstructsPass &pass;
-};
-} // namespace
-
 void LowerConstructsPass::runOnOperation() {
   auto top = getOperation();
   auto *ctxt = &getContext();
@@ -196,8 +167,6 @@ void LowerConstructsPass::runOnOperation() {
   RewritePatternSet patterns(ctxt);
   patterns.insert<SystolicArrayOpLowering>(ctxt);
   target.addIllegalOp<SystolicArrayOp>();
-  patterns.insert<ChannelOpLowering>(ctxt, *this);
-  target.addIllegalOp<ChannelOp>();
 
   if (failed(mlir::applyPartialConversion(top, target, std::move(patterns))))
     signalPassFailure();

test/Dialect/MSFT/constructs.mlir

@@ -50,18 +50,6 @@ hw.module @PE(in %clk: !seq.clock, in %a: i8, in %b: i8, out sum: i8) {
   hw.output %sumDelay1 : i8
 }
 
-// CHECK-LABEL: hw.module @ChannelExample(in %clk : !seq.clock, in %a : i8, out out : i8) {
-// CHECK:         [[REG0:%.+]] = msft.constructs.channel %a %clk "chEx"(2) : i8
-// CHECK:         hw.output [[REG0]] : i8
-// LOWER-LABEL: hw.module @ChannelExample(in %clk : !seq.clock, in %a : i8, out out : i8) {
-// LOWER:         %chEx_0 = seq.compreg sym @chEx_0 %a, %clk : i8
-// LOWER:         %chEx_1 = seq.compreg sym @chEx_1 %chEx_0, %clk : i8
-// LOWER:         hw.output %chEx_1 : i8
-hw.module @ChannelExample (in %clk: !seq.clock, in %a : i8, out out: i8) {
-  %out = msft.constructs.channel %a %clk "chEx" (2) : i8
-  hw.output %out : i8
-}
-
 // CHECK-LABEL: hw.module @foo(in %in0 : i32, in %in1 : i32, in %in2 : i32, in %clk : !seq.clock, out out : i32) {
 // CHECK:       %0 = msft.hlc.linear clock %clk : i32 {
 // CHECK:         %1 = comb.mul %in0, %in1 : i32