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[FIRRTL] Allow local targets to be multiply-instantiated. #7613

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Sep 21, 2024
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[FIRRTL] Allow local targets to be multiply-instantiated. #7613

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103090a
[FIRRTL] Allow local targets to be multiply-instantiated.
mikeurbach Sep 19, 2024
71d7792
Update lib/Dialect/FIRRTL/Transforms/ResolvePaths.cpp
mikeurbach Sep 20, 2024
4d28fb7
Update comment about ambiguity.
mikeurbach Sep 20, 2024
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22 changes: 15 additions & 7 deletions lib/Dialect/FIRRTL/Transforms/LowerClasses.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -275,7 +275,8 @@ struct PathTracker {
// and `owningModule`.
FailureOr<bool> getOrComputeNeedsAltBasePath(Location loc,
StringAttr moduleName,
FModuleOp owningModule);
FModuleOp owningModule,
bool isNonLocal);
FModuleLike module;

// Local data structures.
Expand Down Expand Up @@ -364,7 +365,8 @@ LogicalResult PathTracker::runOnModule() {

FailureOr<bool>
PathTracker::getOrComputeNeedsAltBasePath(Location loc, StringAttr moduleName,
FModuleOp owningModule) {
FModuleOp owningModule,
bool isNonLocal) {

auto it = needsAltBasePathCache.find({moduleName, owningModule});
if (it != needsAltBasePathCache.end())
Expand All @@ -385,7 +387,7 @@ PathTracker::getOrComputeNeedsAltBasePath(Location loc, StringAttr moduleName,
}
// If there is more than one instance of this module, then the path
// operation is ambiguous, which is an error.
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if (!node->hasOneUse()) {
if (isNonLocal && !node->hasOneUse()) {
auto diag = mlir::emitError(loc)
<< "unable to uniquely resolve target due "
"to multiple instantiation";
Expand Down Expand Up @@ -517,8 +519,8 @@ PathTracker::processPathTrackers(const AnnoTarget &target) {
}

// Check if we need an alternative base path.
auto needsAltBasePath =
getOrComputeNeedsAltBasePath(op->getLoc(), moduleName, owningModule);
auto needsAltBasePath = getOrComputeNeedsAltBasePath(
op->getLoc(), moduleName, owningModule, hierPathOp);
if (failed(needsAltBasePath)) {
error = true;
return false;
Expand All @@ -528,6 +530,10 @@ PathTracker::processPathTrackers(const AnnoTarget &target) {
// to the start of the annotation's NLA.
InstanceGraphNode *node = instanceGraph.lookup(moduleName);
while (true) {
// If it's not a non-local target, we don't have to append anything.
if (!hierPathOp)
break;

// If we get to the owning module or the top, we're done.
if (node->getModule() == owningModule || node->noUses())
break;
Expand Down Expand Up @@ -582,8 +588,10 @@ LogicalResult PathTracker::updatePathInfoTable(PathInfoTable &pathInfoTable,
auto &pathInfo = it->second;
if (!inserted) {
assert(pathInfo.loc.has_value() && "all PathInfo should have a Location");
auto diag = emitError(pathInfo.loc.value(), "duplicate identifier found");
diag.attachNote(entry.op->getLoc()) << "other identifier here";
auto diag = emitError(pathInfo.loc.value(),
"path identifier already found, paths must resolve "
"to a unique target");
diag.attachNote(entry.op->getLoc()) << "other path identifier here";
return failure();
}

Expand Down
12 changes: 6 additions & 6 deletions lib/Dialect/FIRRTL/Transforms/ResolvePaths.cpp
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Expand Up @@ -41,6 +41,12 @@ struct PathResolver {
const AnnoPathValue &target,
FlatSymbolRefAttr &result) {

// If the path is empty then this is a local reference and we should not
// construct a HierPathOp.
if (target.instances.empty()) {
return success();
}
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// We want to root this path at the top level module, or in the case of an
// unreachable module, we settle for as high as we can get.
auto module = target.ref.getModule();
Expand Down Expand Up @@ -69,12 +75,6 @@ struct PathResolver {
node = (*node->usesBegin())->getParent();
}

// If the path is empty then this is a local reference and we should not
// construct a HierPathOp.
if (target.instances.empty()) {
return success();
}

// Transform the instances into a list of FlatSymbolRefs.
SmallVector<Attribute> insts;
insts.reserve(target.instances.size());
Expand Down
4 changes: 2 additions & 2 deletions test/Dialect/FIRRTL/lower-classes-errors.mlir
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Expand Up @@ -32,9 +32,9 @@ firrtl.circuit "PathIllegalHierpath" {

firrtl.circuit "PathDuplicateID" {
firrtl.module @PathDuplicateID() {
// expected-error @below {{duplicate identifier found}}
// expected-error @below {{path identifier already found, paths must resolve to a unique target}}
%a = firrtl.wire {annotations = [{class = "circt.tracker", id = distinct[0]<>}]} : !firrtl.uint<8>
// expected-note @below {{other identifier here}}
// expected-note @below {{other path identifier here}}
%b = firrtl.wire {annotations = [{class = "circt.tracker", id = distinct[0]<>}]} : !firrtl.uint<8>
}
}
Expand Down
25 changes: 24 additions & 1 deletion test/Dialect/FIRRTL/lower-classes.mlir
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Expand Up @@ -158,6 +158,7 @@ firrtl.circuit "PathModule" {
// CHECK: hw.hierpath private [[WIRE_PATH:@.+]] [@PathModule::[[WIRE_SYM:@.+]]]
// CHECK: hw.hierpath private [[VECTOR_PATH:@.+]] [@PathModule::[[VECTOR_SYM:@.+]]]
// CHECK: hw.hierpath private [[INST_PATH:@.+]] [@PathModule::@child]
// CHECK: hw.hierpath private [[LOCAL_PATH:@.+]] [@Child]
// CHECK: hw.hierpath private [[MODULE_PATH:@.+]] [@PathModule::@child, @Child::[[NONLOCAL_SYM:@.+]]]

// CHECK: firrtl.module @PathModule(in %in: !firrtl.uint<1> sym [[PORT_SYM]]) {
Expand Down Expand Up @@ -209,7 +210,7 @@ firrtl.circuit "PathModule" {
// CHECK: om.path_create member_instance %basepath [[INST_PATH]]
// CHECK: om.path_create member_instance %basepath [[INST_PATH]]
// CHECK: om.path_create instance %basepath [[INST_PATH]]
// CHECK: om.path_create reference %basepath [[NONLOCAL_PATH]]
// CHECK: om.path_create reference %basepath [[LOCAL_PATH]]
%instance_member_instance = firrtl.path member_instance distinct[4]<>
%instance_member_reference = firrtl.path member_reference distinct[4]<>
%instance = firrtl.path instance distinct[4]<>
Expand Down Expand Up @@ -471,3 +472,25 @@ firrtl.circuit "PathTargetReplaced" {
firrtl.module private @WillBeReplaced(out %output: !firrtl.integer) {
}
}

// CHECK-LABEL: firrtl.circuit "LocalPath"
firrtl.circuit "LocalPath" {
// CHECK: hw.hierpath private [[MODULE_NLA:@.+]] [@Child]
// CHECK: hw.hierpath private [[WIRE_NLA:@.+]] [@Child::[[WIRE_SYM:@.+]]]

firrtl.module @Child() attributes {annotations = [{class = "circt.tracker", id = distinct[0]<>}]} {
// CHECK: firrtl.wire sym [[WIRE_SYM]]
%wire = firrtl.wire {annotations = [{class = "circt.tracker", id = distinct[1]<>}]} : !firrtl.uint<8>
}

firrtl.module @LocalPath() {
// CHECK: om.path_create instance %basepath [[MODULE_NLA]]
%0 = firrtl.path instance distinct[0]<>

// CHECK: om.path_create reference %basepath [[WIRE_NLA]]
%1 = firrtl.path reference distinct[1]<>

firrtl.instance child0 @Child()
firrtl.instance child1 @Child()
}
}
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To elaborate on my comment... What I'm concerned about is if there is a way to rewrite this circuit such that @Child is duplicated into @Child0 and @Child1. What are the trackers used then? After deduplication, it would seem like this would result in non-local annotation trackers which would then trip the error checking logic.

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I see. The main way I have noticed something like this happening is when PrefixModules clones modules. You can set up an example that would cause @Child to @Child0 and @Child1, each with a local annotation with the same distinct ID. This would then error out in LowerClasses here:

circt/lib/Dialect/FIRRTL/Transforms/LowerClasses.cpp

Lines 585 to 586 in afd61f2

auto diag = emitError(pathInfo.loc.value(), "duplicate identifier found");
diag.attachNote(entry.op->getLoc()) << "other identifier here";

Which is equivalent to this existing check:

circt/lib/Dialect/FIRRTL/Transforms/EmitOMIR.cpp

Lines 650 to 654 in afd61f2

auto diag = op->emitError(omirTrackerAnnoClass)
<< " annotation with same ID already found, must resolve "
"to single target";
diag.attachNote(it->second.op->getLoc())
<< "tracker with same ID already found here";

Note that PrefixModules happens after Dedup, but it might be possible to hit a scenario where Dedup makes local annotations non-local, and that could potentially fail the single-instantiation check, which I think is what you're referring to.

I guess my thought is with this PR, we can support some local annotations end-to-end, and in the cases where it doesn't work, we'd hit a well defined error case. So, this should support some cases, but it shouldn't allow any ambiguous cases through; those should still error in the expected ways.

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Does this help assuage your concerns? If the current state is fine, I'll go ahead and merge this PR.

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I have zero problems with this PR! Good to go!

I'm bringing up this problem with dedup because it's a general problem with any annotation representation. If this fix gets you further, please go for it. 👍

Annotations are generally problematic and we're slowly tackling getting off them. You're aware of the problems.

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Yep makes sense, thanks. I think with this we'll at least be at parity with what we could do with the tracker annotations and EmitOMIR. Excited to design a more dataflow-y representation for paths.

12 changes: 7 additions & 5 deletions test/Dialect/FIRRTL/resolve-paths-errors.mlir
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Expand Up @@ -75,13 +75,16 @@ firrtl.module @VectorTarget(in %a : !firrtl.vector<uint<1>, 1>) {
firrtl.circuit "AmbiguousPath" {
firrtl.module @AmbiguousPath() {
// expected-error @below {{unable to uniquely resolve target due to multiple instantiation}}
%0 = firrtl.unresolved_path "OMReferenceTarget:~AmbiguousPath|Child"
%0 = firrtl.unresolved_path "OMReferenceTarget:~AmbiguousPath|Child/grandchild:GrandChild"
// expected-note @below {{instance here}}
firrtl.instance child0 @Child()
// expected-note @below {{instance here}}
firrtl.instance child1 @Child()
}
firrtl.module @Child() {}
firrtl.module @Child() {
firrtl.instance grandchild @GrandChild()
}
firrtl.module @GrandChild() {}
}

// -----
Expand All @@ -102,18 +105,17 @@ firrtl.class @Test(){

firrtl.circuit "UpwardPath" {
firrtl.module @UpwardPath() {
%wire = firrtl.wire : !firrtl.uint<8>
firrtl.instance child @Child()
}

firrtl.module @Child() {
%om = firrtl.object @OM()

%wire = firrtl.wire : !firrtl.uint<8>
}

firrtl.class @OM(){
// expected-error @below {{unable to resolve path relative to owning module "Child"}}
%0 = firrtl.unresolved_path "OMReferenceTarget:~UpwardPath|UpwardPath>wire"
%0 = firrtl.unresolved_path "OMReferenceTarget:~UpwardPath|UpwardPath/child:Child>wire"
}
}

24 changes: 24 additions & 0 deletions test/Dialect/FIRRTL/resolve-paths.mlir
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Expand Up @@ -91,6 +91,30 @@ firrtl.module @Child() {

// -----

// CHECK-LABEL: firrtl.circuit "LocalPath"
firrtl.circuit "LocalPath" {
// CHECK: firrtl.module @LocalPath()
firrtl.module @LocalPath() {
// CHECK: %0 = firrtl.path instance distinct[0]<>
%0 = firrtl.unresolved_path "OMInstanceTarget:~LocalPath|Child"

// CHECK: %1 = firrtl.path reference distinct[1]<>
%1 = firrtl.unresolved_path "OMReferenceTarget:~LocalPath|Child>wire"

// CHECK: firrtl.instance child0 @Child()
// CHECK: firrtl.instance child1 @Child()
firrtl.instance child0 @Child()
firrtl.instance child1 @Child()
}
// CHECK: firrtl.module @Child() attributes {annotations = [{class = "circt.tracker", id = distinct[0]<>}]}
firrtl.module @Child() {
// CHECK: %wire = firrtl.wire {annotations = [{class = "circt.tracker", id = distinct[1]<>}]} : !firrtl.uint<8>
%wire = firrtl.wire : !firrtl.uint<8>
}
}

// -----

// CHECK-LABEL: firrtl.circuit "PathMinimization"
firrtl.circuit "PathMinimization" {
// CHECK: firrtl.module @PathMinimization()
Expand Down
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