[Mlir-commits] [mlir] 3e746bd - Allowing RDV to call `getArgOperandsMutable()` (#160415)
llvmlistbot at llvm.org
llvmlistbot at llvm.org
Fri Sep 26 06:30:51 PDT 2025
Author: Francisco Geiman Thiesen
Date: 2025-09-26T15:30:46+02:00
New Revision: 3e746bd8fb6aece3c6d56dae4a9a7f0a7ec61859
URL: https://github.com/llvm/llvm-project/commit/3e746bd8fb6aece3c6d56dae4a9a7f0a7ec61859
DIFF: https://github.com/llvm/llvm-project/commit/3e746bd8fb6aece3c6d56dae4a9a7f0a7ec61859.diff
LOG: Allowing RDV to call `getArgOperandsMutable()` (#160415)
## Problem
`RemoveDeadValues` can legally drop dead function arguments on private
`func.func` callees. But call-sites to such functions aren't fixed if
the call operation keeps its call arguments in a **segmented operand
group** (i.ie, uses `AttrSizedOperandSegments`), unless the call op
implements `getArgOperandsMutable` and the RDV pass actually uses it.
## Fix
When RDV decides to drop callee function args, it should, for each
call-site that implements `CallOpInterface`, **shrink the call's
argument segment** via `getArgOperandsMutable()` using the same dead-arg
indices. This keeps both the flat operand list and the
`operand_segment_sizes` attribute in sync (that's what
`MutableOperandRange` does when bound to the segment).
## Note
This change is a no-op for:
* call ops without segment operands (they still get their flat operands
erased via the generic path)
* call ops whose calle args weren't dropped (public, external,
non-`func-func`, unresolved symbol, etc)
* `llvm.call`/`llvm.invoke` (RDV doesn't drop `llvm.func` args
---------
Co-authored-by: Mehdi Amini <joker.eph at gmail.com>
Added:
mlir/test/Transforms/remove-dead-values-call-segments.mlir
Modified:
mlir/lib/Transforms/RemoveDeadValues.cpp
mlir/test/lib/Dialect/Test/TestDialect.cpp
mlir/test/lib/Dialect/Test/TestOps.td
Removed:
################################################################################
diff --git a/mlir/lib/Transforms/RemoveDeadValues.cpp b/mlir/lib/Transforms/RemoveDeadValues.cpp
index 0e84b6dd17f29..fe74f3d4632a6 100644
--- a/mlir/lib/Transforms/RemoveDeadValues.cpp
+++ b/mlir/lib/Transforms/RemoveDeadValues.cpp
@@ -88,6 +88,8 @@ struct FunctionToCleanUp {
struct OperationToCleanup {
Operation *op;
BitVector nonLive;
+ Operation *callee =
+ nullptr; // Optional: For CallOpInterface ops, stores the callee function
};
struct BlockArgsToCleanup {
@@ -306,19 +308,19 @@ static void processFuncOp(FunctionOpInterface funcOp, Operation *module,
nonLiveSet.insert(arg);
}
- // Do (2).
+ // Do (2). (Skip creating generic operand cleanup entries for call ops.
+ // Call arguments will be removed in the call-site specific segment-aware
+ // cleanup, avoiding generic eraseOperands bitvector mechanics.)
SymbolTable::UseRange uses = *funcOp.getSymbolUses(module);
for (SymbolTable::SymbolUse use : uses) {
Operation *callOp = use.getUser();
assert(isa<CallOpInterface>(callOp) && "expected a call-like user");
- // The number of operands in the call op may not match the number of
- // arguments in the func op.
- BitVector nonLiveCallOperands(callOp->getNumOperands(), false);
- SmallVector<OpOperand *> callOpOperands =
- operandsToOpOperands(cast<CallOpInterface>(callOp).getArgOperands());
- for (int index : nonLiveArgs.set_bits())
- nonLiveCallOperands.set(callOpOperands[index]->getOperandNumber());
- cl.operands.push_back({callOp, nonLiveCallOperands});
+ // Push an empty operand cleanup entry so that call-site specific logic in
+ // cleanUpDeadVals runs (it keys off CallOpInterface). The BitVector is
+ // intentionally all false to avoid generic erasure.
+ // Store the funcOp as the callee to avoid expensive symbol lookup later.
+ cl.operands.push_back({callOp, BitVector(callOp->getNumOperands(), false),
+ funcOp.getOperation()});
}
// Do (3).
@@ -746,6 +748,10 @@ static void cleanUpDeadVals(RDVFinalCleanupList &list) {
// 3. Functions
LDBG() << "Cleaning up " << list.functions.size() << " functions";
+ // Record which function arguments were erased so we can shrink call-site
+ // argument segments for CallOpInterface operations (e.g. ops using
+ // AttrSizedOperandSegments) in the next phase.
+ DenseMap<Operation *, BitVector> erasedFuncArgs;
for (auto &f : list.functions) {
LDBG() << "Cleaning up function: " << f.funcOp.getOperation()->getName();
LDBG() << " Erasing " << f.nonLiveArgs.count() << " non-live arguments";
@@ -754,17 +760,52 @@ static void cleanUpDeadVals(RDVFinalCleanupList &list) {
// Some functions may not allow erasing arguments or results. These calls
// return failure in such cases without modifying the function, so it's okay
// to proceed.
- (void)f.funcOp.eraseArguments(f.nonLiveArgs);
+ if (succeeded(f.funcOp.eraseArguments(f.nonLiveArgs))) {
+ // Record only if we actually erased something.
+ if (f.nonLiveArgs.any())
+ erasedFuncArgs.try_emplace(f.funcOp.getOperation(), f.nonLiveArgs);
+ }
(void)f.funcOp.eraseResults(f.nonLiveRets);
}
// 4. Operands
LDBG() << "Cleaning up " << list.operands.size() << " operand lists";
for (OperationToCleanup &o : list.operands) {
- if (o.op->getNumOperands() > 0) {
- LDBG() << "Erasing " << o.nonLive.count()
- << " non-live operands from operation: "
- << OpWithFlags(o.op, OpPrintingFlags().skipRegions());
+ // Handle call-specific cleanup only when we have a cached callee reference.
+ // This avoids expensive symbol lookup and is defensive against future
+ // changes.
+ bool handledAsCall = false;
+ if (o.callee && isa<CallOpInterface>(o.op)) {
+ auto call = cast<CallOpInterface>(o.op);
+ auto it = erasedFuncArgs.find(o.callee);
+ if (it != erasedFuncArgs.end()) {
+ const BitVector &deadArgIdxs = it->second;
+ MutableOperandRange args = call.getArgOperandsMutable();
+ // First, erase the call arguments corresponding to erased callee
+ // args. We iterate backwards to preserve indices.
+ for (unsigned argIdx : llvm::reverse(deadArgIdxs.set_bits()))
+ args.erase(argIdx);
+ // If this operand cleanup entry also has a generic nonLive bitvector,
+ // clear bits for call arguments we already erased above to avoid
+ // double-erasing (which could impact other segments of ops with
+ // AttrSizedOperandSegments).
+ if (o.nonLive.any()) {
+ // Map the argument logical index to the operand number(s) recorded.
+ int operandOffset = call.getArgOperands().getBeginOperandIndex();
+ for (int argIdx : deadArgIdxs.set_bits()) {
+ int operandNumber = operandOffset + argIdx;
+ if (operandNumber < static_cast<int>(o.nonLive.size()))
+ o.nonLive.reset(operandNumber);
+ }
+ }
+ handledAsCall = true;
+ }
+ }
+ // Perform generic operand erasure for:
+ // - Non-call operations
+ // - Call operations without cached callee (where handledAsCall is false)
+ // But skip call operations that were already handled via segment-aware path
+ if (!handledAsCall && o.nonLive.any()) {
o.op->eraseOperands(o.nonLive);
}
}
diff --git a/mlir/test/Transforms/remove-dead-values-call-segments.mlir b/mlir/test/Transforms/remove-dead-values-call-segments.mlir
new file mode 100644
index 0000000000000..fed9cabbd2ee8
--- /dev/null
+++ b/mlir/test/Transforms/remove-dead-values-call-segments.mlir
@@ -0,0 +1,23 @@
+// RUN: mlir-opt --split-input-file --remove-dead-values --mlir-print-op-generic %s | FileCheck %s --check-prefix=GEN
+
+// -----
+// Private callee: both args become dead after internal DCE; RDV drops callee
+// args and shrinks the *args* segment on the call-site to zero; sizes kept in
+// sync.
+
+module {
+ func.func private @callee(%x: i32, %y: i32) {
+ %u = arith.addi %x, %x : i32 // %y is dead
+ return
+ }
+
+ func.func @caller(%a: i32, %b: i32) {
+ // args segment initially has 2 operands.
+ "test.call_with_segments"(%a, %b) { callee = @callee,
+ operandSegmentSizes = array<i32: 0, 2, 0> } : (i32, i32) -> ()
+ return
+ }
+}
+
+// GEN: "test.call_with_segments"() <{callee = @callee, operandSegmentSizes = array<i32: 0, 0, 0>}> : () -> ()
+// ^ args shrank from 2 -> 0
diff --git a/mlir/test/lib/Dialect/Test/TestDialect.cpp b/mlir/test/lib/Dialect/Test/TestDialect.cpp
index 987e8f3654ce8..21d75f58b0a3a 100644
--- a/mlir/test/lib/Dialect/Test/TestDialect.cpp
+++ b/mlir/test/lib/Dialect/Test/TestDialect.cpp
@@ -431,3 +431,47 @@ void TestDialect::getCanonicalizationPatterns(
RewritePatternSet &results) const {
results.add(&dialectCanonicalizationPattern);
}
+
+//===----------------------------------------------------------------------===//
+// TestCallWithSegmentsOp
+//===----------------------------------------------------------------------===//
+// The op `test.call_with_segments` models a call-like operation whose operands
+// are divided into 3 variadic segments: `prefix`, `args`, and `suffix`.
+// Only the middle segment represents the actual call arguments. The op uses
+// the AttrSizedOperandSegments trait, so we can derive segment boundaries from
+// the generated `operandSegmentSizes` attribute. We provide custom helpers to
+// expose the logical call arguments as both a read-only range and a mutable
+// range bound to the proper segment so that insertion/erasure updates the
+// attribute automatically.
+
+// Segment layout indices in the DenseI32ArrayAttr: [prefix, args, suffix].
+static constexpr unsigned kTestCallWithSegmentsArgsSegIndex = 1;
+
+Operation::operand_range CallWithSegmentsOp::getArgOperands() {
+ // Leverage generated getters for segment sizes: slice between prefix and
+ // suffix using current operand list.
+ return getOperation()->getOperands().slice(getPrefix().size(),
+ getArgs().size());
+}
+
+MutableOperandRange CallWithSegmentsOp::getArgOperandsMutable() {
+ Operation *op = getOperation();
+
+ // Obtain the canonical segment size attribute name for this op.
+ auto segName =
+ CallWithSegmentsOp::getOperandSegmentSizesAttrName(op->getName());
+ auto sizesAttr = op->getAttrOfType<DenseI32ArrayAttr>(segName);
+ assert(sizesAttr && "missing operandSegmentSizes attribute on op");
+
+ // Compute the start and length of the args segment from the prefix size and
+ // args size stored in the attribute.
+ auto sizes = sizesAttr.asArrayRef();
+ unsigned start = static_cast<unsigned>(sizes[0]); // prefix size
+ unsigned len = static_cast<unsigned>(sizes[1]); // args size
+
+ NamedAttribute segNamed(segName, sizesAttr);
+ MutableOperandRange::OperandSegment binding{kTestCallWithSegmentsArgsSegIndex,
+ segNamed};
+
+ return MutableOperandRange(op, start, len, {binding});
+}
diff --git a/mlir/test/lib/Dialect/Test/TestOps.td b/mlir/test/lib/Dialect/Test/TestOps.td
index d9bbb3261febc..6ea27187655ee 100644
--- a/mlir/test/lib/Dialect/Test/TestOps.td
+++ b/mlir/test/lib/Dialect/Test/TestOps.td
@@ -3746,4 +3746,47 @@ def TestOpWithSuccessorRef : TEST_Op<"dummy_op_with_successor_ref"> {
}];
}
+def CallWithSegmentsOp : TEST_Op<"call_with_segments",
+ [AttrSizedOperandSegments,
+ DeclareOpInterfaceMethods<CallOpInterface>]> {
+ let summary = "test call op with segmented args";
+ let arguments = (ins
+ FlatSymbolRefAttr:$callee,
+ Variadic<AnyType>:$prefix, // non-arg segment (e.g., 'in')
+ Variadic<AnyType>:$args, // <-- the call *arguments* segment
+ Variadic<AnyType>:$suffix // non-arg segment (e.g., 'out')
+ );
+ let results = (outs);
+ let assemblyFormat = [{
+ $callee `(` $prefix `:` type($prefix) `)`
+ `(` $args `:` type($args) `)`
+ `(` $suffix `:` type($suffix) `)` attr-dict
+ }];
+
+ // Provide stub implementations for the ArgAndResultAttrsOpInterface.
+ let extraClassDeclaration = [{
+ ::mlir::ArrayAttr getArgAttrsAttr() { return {}; }
+ ::mlir::ArrayAttr getResAttrsAttr() { return {}; }
+ void setArgAttrsAttr(::mlir::ArrayAttr) {}
+ void setResAttrsAttr(::mlir::ArrayAttr) {}
+ ::mlir::Attribute removeArgAttrsAttr() { return {}; }
+ ::mlir::Attribute removeResAttrsAttr() { return {}; }
+ }];
+
+ let extraClassDefinition = [{
+ ::mlir::CallInterfaceCallable $cppClass::getCallableForCallee() {
+ if (auto sym = (*this)->getAttrOfType<::mlir::SymbolRefAttr>("callee"))
+ return ::mlir::CallInterfaceCallable(sym);
+ return ::mlir::CallInterfaceCallable();
+ }
+ void $cppClass::setCalleeFromCallable(::mlir::CallInterfaceCallable callee) {
+ if (auto sym = callee.dyn_cast<::mlir::SymbolRefAttr>())
+ (*this)->setAttr("callee", sym);
+ else
+ (*this)->removeAttr("callee");
+ }
+ }];
+}
+
+
#endif // TEST_OPS
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