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Implement a handler for XLS->LLVM conversion for the cover op. #4011

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Implement a handler for XLS->LLVM conversion for the cover op. #4011

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24 changes: 24 additions & 0 deletions xls/jit/BUILD
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Original file line number Diff line number Diff line change
Expand Up @@ -1381,12 +1381,36 @@ xls_aot_generate(
with_msan = XLS_IS_MSAN_BUILD,
)

xls_dslx_library(
name = "coverage_test_dslx",
srcs = ["coverage_test.x"],
)

xls_dslx_ir(
name = "coverage_test_ir",
dslx_top = "run_coverage",
ir_conv_args = {"lower_to_proc_scoped_channels": "true"},
library = ":coverage_test_dslx",
)

xls_aot_generate(
name = "coverage_test_aot",
testonly = True,
src = ":coverage_test_ir",
enable_llvm_coverage = True,
salt_symbols = False,
top = "run_coverage",
top_type = "FUNCTION",
with_msan = XLS_IS_MSAN_BUILD,
)

# Tests that the coverage instrumentation can be enabled.
build_test(
name = "jit_build_test",
targets = [
":multi_function_aot_coverage",
":multi_function_aot_coverage_jobs",
":coverage_test_aot",
],
)

Expand Down
18 changes: 18 additions & 0 deletions xls/jit/coverage_test.x
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@@ -0,0 +1,18 @@
// Copyright 2026 The XLS Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

pub fn run_coverage(a: u32, b: u32, c: u32) -> u32 {
cover!("a_plus_b_gt_c", a + b > c);
a + b + c
}
23 changes: 21 additions & 2 deletions xls/jit/ir_builder_visitor.cc
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Expand Up @@ -43,6 +43,7 @@
#include "llvm/include/llvm/IR/DerivedTypes.h"
#include "llvm/include/llvm/IR/GEPNoWrapFlags.h"
#include "llvm/include/llvm/IR/IRBuilder.h"
#include "llvm/include/llvm/IR/InlineAsm.h"
#include "llvm/include/llvm/IR/Instructions.h"
#include "llvm/include/llvm/IR/Intrinsics.h"
#include "llvm/include/llvm/IR/LLVMContext.h"
Expand Down Expand Up @@ -323,7 +324,7 @@ std::vector<std::string> NumberedStrings(std::string_view s, int64_t count) {
return result;
}

// Returns the concatentation of two vectors.
// Returns the concatenation of two vectors.
std::vector<std::string> ConcatVectors(absl::Span<const std::string> a,
absl::Span<const std::string> b) {
std::vector<std::string> result(a.begin(), a.end());
Expand Down Expand Up @@ -2295,8 +2296,26 @@ absl::Status IrBuilderVisitor::HandleCover(Cover* cover) {
// support to the JIT.
XLS_ASSIGN_OR_RETURN(NodeIrContext node_context,
NewNodeIrContext(cover, {"condition"}));
std::optional<llvm::IRBuilder<>*> exit_builder;
if (jit_context_.llvm_compiler().include_llvm_coverage()) {
llvm::IRBuilder<>& b = node_context.entry_builder();
llvm::Value* cond = Truthiness(node_context.LoadOperand(0), b);
LlvmIfThen if_then = CreateIfThen(cond, b, cover->GetName());
llvm::FunctionType* ft =
llvm::FunctionType::get(llvm::Type::getVoidTy(ctx()), {}, false);
// We invoke inline asm (with hasSideEffects=true) to ensure that the
// coverage point is not optimized away.
llvm::InlineAsm* ia =
llvm::InlineAsm::get(ft, absl::StrCat("# coverage: ", cover->label()),
"", /*hasSideEffects=*/true);
if_then.then_builder->CreateCall(ia, {});

exit_builder = if_then.Finalize().get();
}

llvm::Value* token = type_converter()->GetToken();
return FinalizeNodeIrContextWithValue(std::move(node_context), token);
return FinalizeNodeIrContextWithValue(std::move(node_context), token,
exit_builder);
}

absl::Status IrBuilderVisitor::HandleDecode(Decode* decode) {
Expand Down
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