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馃悰 Reject nonlinear Hadamard-lifting inputs safely #2309

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馃悰 Reject nonlinear Hadamard-lifting inputs safely #2309

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5 changes: 5 additions & 0 deletions mlir/lib/Dialect/QCO/Transforms/Optimizations/HadamardLifting.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
#include "mlir/Dialect/MQT/Utils/Modifiers.h"
#include "mlir/Dialect/QCO/IR/QCOInterfaces.h"
#include "mlir/Dialect/QCO/IR/QCOOps.h"
#include "mlir/Dialect/QCO/QCOUtils.h"
#include "mlir/Dialect/QCO/Transforms/Passes.h"

#include <llvm/ADT/STLExtras.h>
Expand Down Expand Up @@ -228,6 +229,10 @@ struct HadamardLifting final : impl::HadamardLiftingBase<HadamardLifting> {
void runOnOperation() override {
auto op = getOperation();
auto* ctx = &getContext();
if (failed(qco::verifyLinearity(op))) {
signalPassFailure();
return;
}
Comment on lines +232 to +235

@burgholzer burgholzer Sep 1, 2026

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Hm. I am not sure we should actually be adding this in front of every pass.
Passes can expect valid IR. They should not have to verify that it is valid.
I'd rather drop that in cases like here.
Does that make sense?


// Define the set of patterns to use.
RewritePatternSet patterns(ctx);
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53 changes: 53 additions & 0 deletions mlir/unittests/Dialect/QCO/Transforms/Optimizations/test_qco_hadamard_lifting.cpp
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Expand Up @@ -20,8 +20,11 @@
#include <mlir/Dialect/MemRef/IR/MemRef.h>
#include <mlir/IR/BuiltinOps.h>
#include <mlir/IR/DialectRegistry.h>
#include <mlir/IR/OperationSupport.h>
#include <mlir/IR/OwningOpRef.h>
#include <mlir/IR/Value.h>
#include <mlir/IR/Verifier.h>
#include <mlir/Parser/Parser.h>
#include <mlir/Pass/PassManager.h>
#include <mlir/Support/LLVM.h>
#include <mlir/Support/LogicalResult.h>
Expand Down Expand Up @@ -81,6 +84,56 @@ class QCOHadamardLiftingTest : public testing::Test {

} // namespace

TEST_F(QCOHadamardLiftingTest, HandlesUnusedPauliOutput) {
auto input = parseSourceString<ModuleOp>(R"mlir(
module {
func.func @main() {
%q = qco.static 0 : !qco.qubit
%unused = qco.x %q : !qco.qubit -> !qco.qubit
return
}
}
)mlir",
Comment on lines +87 to +96

@burgholzer burgholzer Sep 1, 2026

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This is invalid QCO IR.
We should really enforce the invariant that passes may assume IR to be valid.
We may check in tests that this is actually true before and after passes, but the corner case checking in all of our passes can be reduced.
Even more so can the amount of tests that check these invalid IR programs.
This extends well beyond this PR.

&context);
ASSERT_TRUE(input);
ASSERT_TRUE(succeeded(verify(*input)));
OwningOpRef<ModuleOp> original(input->clone());

EXPECT_TRUE(failed(runHadamardLiftingPass(*input)));
EXPECT_TRUE(OperationEquivalence::isEquivalentTo(
input->getOperation(), original->getOperation(),
OperationEquivalence::Flags::None));
}

TEST_F(QCOHadamardLiftingTest, HandlesUnusedCnotControlOutput) {
auto input = parseSourceString<ModuleOp>(R"mlir(
module {
func.func @main() {
%control = qco.static 0 : !qco.qubit
%target = qco.static 1 : !qco.qubit
%unused, %target_out = qco.ctrl(%control) targets(%arg = %target) {
%body = qco.x %arg : !qco.qubit -> !qco.qubit
qco.yield %body : !qco.qubit
} : ({!qco.qubit}, {!qco.qubit})
-> ({!qco.qubit}, {!qco.qubit})
%hadamard = qco.h %target_out : !qco.qubit -> !qco.qubit
%measured, %result = qco.measure %hadamard : !qco.qubit
qco.sink %measured : !qco.qubit
return
}
}
)mlir",
&context);
ASSERT_TRUE(input);
ASSERT_TRUE(succeeded(verify(*input)));
OwningOpRef<ModuleOp> original(input->clone());

EXPECT_TRUE(failed(runHadamardLiftingPass(*input)));
EXPECT_TRUE(OperationEquivalence::isEquivalentTo(
input->getOperation(), original->getOperation(),
OperationEquivalence::Flags::None));
}

// ##################################################
// # Raise Hadamard over uncontrolled Pauli gate Tests
// ##################################################
Expand Down
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