Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

[FIRRTL] Make IMDCE work for ops w/ regions/blocks #7881

Open
wants to merge 1 commit into
base: main
Choose a base branch
from
Open

[FIRRTL] Make IMDCE work for ops w/ regions/blocks #7881

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
70 changes: 40 additions & 30 deletions lib/Dialect/FIRRTL/Transforms/IMDeadCodeElim.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
#include "circt/Dialect/HW/InnerSymbolTable.h"
#include "circt/Support/Debug.h"
#include "mlir/IR/ImplicitLocOpBuilder.h"
#include "mlir/IR/Iterators.h"
#include "mlir/IR/Threading.h"
#include "mlir/Interfaces/SideEffectInterfaces.h"
#include "mlir/Pass/Pass.h"
Expand Down Expand Up @@ -240,15 +241,16 @@ void IMDeadCodeElimPass::markBlockExecutable(Block *block) {
if (!executableBlocks.insert(block).second)
return; // Already executable.

auto fmodule = cast<FModuleOp>(block->getParentOp());
if (fmodule.isPublic())
auto fmodule = dyn_cast<FModuleOp>(block->getParentOp());
if (fmodule && fmodule.isPublic())
markAlive(fmodule);

// Mark ports with don't touch as alive.
for (auto blockArg : block->getArguments())
if (hasDontTouch(blockArg)) {
markAlive(blockArg);
markAlive(fmodule);
if (fmodule)
markAlive(fmodule);
}

for (auto &op : *block) {
Expand All @@ -264,6 +266,12 @@ void IMDeadCodeElimPass::markBlockExecutable(Block *block) {
else if (hasUnknownSideEffect(&op))
markUnknownSideEffectOp(&op);

// Recursively mark any blocks contained within these operations as
// executable.
for (auto &region : op.getRegions())
for (auto &block : region.getBlocks())
markBlockExecutable(&block);

// TODO: Handle attach etc.
}
}
Expand Down Expand Up @@ -561,33 +569,35 @@ void IMDeadCodeElimPass::rewriteModuleBody(FModuleOp module) {
std::bind(removeDeadNonLocalAnnotations, -1, std::placeholders::_1));

// Walk the IR bottom-up when deleting operations.
for (auto &op : llvm::make_early_inc_range(llvm::reverse(*body))) {
// Connects to values that we found to be dead can be dropped.
if (auto connect = dyn_cast<FConnectLike>(op)) {
if (isAssumedDead(connect.getDest())) {
LLVM_DEBUG(llvm::dbgs() << "DEAD: " << connect << "\n";);
connect.erase();
++numErasedOps;
}
continue;
}

// Delete dead wires, regs, nodes and alloc/read ops.
if ((isDeclaration(&op) || !hasUnknownSideEffect(&op)) &&
isAssumedDead(&op)) {
LLVM_DEBUG(llvm::dbgs() << "DEAD: " << op << "\n";);
assert(op.use_empty() && "users should be already removed");
op.erase();
++numErasedOps;
continue;
}

// Remove non-sideeffect op using `isOpTriviallyDead`.
if (mlir::isOpTriviallyDead(&op)) {
op.erase();
++numErasedOps;
}
}
module.walk<mlir::WalkOrder::PostOrder, mlir::ReverseIterator>(
[&](Operation *op) {
// Connects to values that we found to be dead can be dropped.
LLVM_DEBUG(llvm::dbgs() << "Visit: " << *op << "\n");
if (auto connect = dyn_cast<FConnectLike>(op)) {
if (isAssumedDead(connect.getDest())) {
LLVM_DEBUG(llvm::dbgs() << "DEAD: " << connect << "\n";);
connect.erase();
++numErasedOps;
}
return;
}

// Delete dead wires, regs, nodes and alloc/read ops.
if ((isDeclaration(op) || !hasUnknownSideEffect(op)) &&
isAssumedDead(op)) {
LLVM_DEBUG(llvm::dbgs() << "DEAD: " << *op << "\n";);
assert(op->use_empty() && "users should be already removed");
op->erase();
++numErasedOps;
return;
}

// Remove non-sideeffect op using `isOpTriviallyDead`.
if (mlir::isOpTriviallyDead(op)) {
op->erase();
++numErasedOps;
}
});
}

void IMDeadCodeElimPass::rewriteModuleSignature(FModuleOp module) {
Expand Down
25 changes: 25 additions & 0 deletions test/Dialect/FIRRTL/imdce.mlir
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -617,3 +617,28 @@ firrtl.circuit "OMIRRemoval" {
]} : !firrtl.uint<4>
}
}

// -----

// Test that an operation with a nested block user will be removed (and not
// crash).
//
// CHECK-LAEBL: "Foo"
firrtl.circuit "Foo" {
firrtl.layer @A bind {}
sv.macro.decl @B["B"]
// CHECK-NOT: @Bar
firrtl.module private @Bar() {}
firrtl.module @Foo() {
// CHECK-LABEL: firrtl.layerblock @A
firrtl.layerblock @A {
// CHECK-NOT: firrtl.instance
firrtl.instance bar @Bar()
// CHECK-LABEL: sv.ifdef @B
sv.ifdef @B {
// CHECK-NOT: firrtl.instance
firrtl.instance bar2 @Bar()
}
}
}
}
Loading