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Switch to BumpPtrAllocator for C-string storage (#6550)

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This keeps the allocations cheap and simplifies the code. It was
inspired by the need to expand param files, but
no functionality changed yet.
This commit is contained in:
Chandler Carruth
2026-01-07 02:53:31 +00:00
committed by GitHub
parent 505b1c86b9
commit eecbb7e508
7 changed files with 34 additions and 44 deletions
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common/string_helpers.cpp
+5 -18
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@@ -18,6 +18,7 @@
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/ConvertUTF.h"
namespace Carbon {
@@ -211,33 +212,19 @@ auto StringRefContainsPointer(llvm::StringRef ref, const char* ptr) -> bool {
auto BuildCStrArgs(llvm::StringRef tool_path,
llvm::ArrayRef<llvm::StringRef> args,
llvm::OwningArrayRef<char>& cstr_arg_storage)
llvm::BumpPtrAllocator& alloc)
-> llvm::SmallVector<const char*, 64> {
return BuildCStrArgs(tool_path, /*prefix_args=*/{}, args, cstr_arg_storage);
return BuildCStrArgs(tool_path, /*prefix_args=*/{}, args, alloc);
}
auto BuildCStrArgs(llvm::StringRef tool_path,
llvm::ArrayRef<std::string> prefix_args,
llvm::ArrayRef<llvm::StringRef> args,
llvm::OwningArrayRef<char>& cstr_arg_storage)
llvm::BumpPtrAllocator& alloc)
-> llvm::SmallVector<const char*, 64> {
// Render the arguments into null-terminated C-strings. Command lines can get
// quite long in build systems so this tries to minimize the memory allocation
// overhead.
// Precompute the total C-string data size needed.
int total_size = tool_path.size() + 1;
for (llvm::StringRef arg : args) {
// Accumulate both the string size and a null terminator byte.
total_size += arg.size() + 1;
}
// Allocate one chunk of storage for the actual C-strings, and reserve a
// vector of pointers into the storage.
cstr_arg_storage = llvm::OwningArrayRef<char>(total_size);
ssize_t i = 0;
auto make_cstr = [&](llvm::StringRef arg) {
char* cstr = &cstr_arg_storage[i];
char* cstr = alloc.Allocate<char>(arg.size() + 1);
memcpy(cstr, arg.data(), arg.size());
cstr[arg.size()] = '\0';
i += arg.size() + 1;
common/string_helpers.h
+3 -2
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@@ -12,6 +12,7 @@
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Allocator.h"
namespace Carbon {
@@ -44,7 +45,7 @@ auto StringRefContainsPointer(llvm::StringRef ref, const char* ptr) -> bool;
// lines to avoid extra allocations and growth passes.
auto BuildCStrArgs(llvm::StringRef tool_path,
llvm::ArrayRef<llvm::StringRef> args,
llvm::OwningArrayRef<char>& cstr_arg_storage)
llvm::BumpPtrAllocator& alloc)
-> llvm::SmallVector<const char*, 64>;
// An overload of `BuildCStrArgs` with the same core behavior as the above, but
@@ -61,7 +62,7 @@ auto BuildCStrArgs(llvm::StringRef tool_path,
auto BuildCStrArgs(llvm::StringRef tool_path,
llvm::ArrayRef<std::string> prefix_args,
llvm::ArrayRef<llvm::StringRef> args,
llvm::OwningArrayRef<char>& cstr_arg_storage)
llvm::BumpPtrAllocator& alloc)
-> llvm::SmallVector<const char*, 64>;
} // namespace Carbon
common/string_helpers_test.cpp
+15 -14
View File
@@ -12,6 +12,7 @@
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Allocator.h"
using ::testing::Eq;
using ::testing::Optional;
@@ -233,23 +234,23 @@ TEST(ParseBlockStringLiteral, OkMultipleSlashes) {
}
TEST(BuildCStrArgs, NoArgs) {
llvm::OwningArrayRef<char> storage;
auto result = BuildCStrArgs("tool", {}, storage);
llvm::BumpPtrAllocator alloc;
auto result = BuildCStrArgs("tool", {}, alloc);
ASSERT_THAT(result.size(), Eq(1));
EXPECT_THAT(result[0], StrEq("tool"));
}
TEST(BuildCStrArgs, OneArg) {
llvm::OwningArrayRef<char> storage;
auto result = BuildCStrArgs("tool", {"arg1"}, storage);
llvm::BumpPtrAllocator alloc;
auto result = BuildCStrArgs("tool", {"arg1"}, alloc);
ASSERT_THAT(result.size(), Eq(2));
EXPECT_THAT(result[0], StrEq("tool"));
EXPECT_THAT(result[1], StrEq("arg1"));
}
TEST(BuildCStrArgs, MultipleArgs) {
llvm::OwningArrayRef<char> storage;
auto result = BuildCStrArgs("tool", {"arg1", "arg2"}, storage);
llvm::BumpPtrAllocator alloc;
auto result = BuildCStrArgs("tool", {"arg1", "arg2"}, alloc);
ASSERT_THAT(result.size(), Eq(3));
EXPECT_THAT(result[0], StrEq("tool"));
EXPECT_THAT(result[1], StrEq("arg1"));
@@ -257,16 +258,16 @@ TEST(BuildCStrArgs, MultipleArgs) {
}
TEST(BuildCStrArgsWithPrefix, NoArgs) {
llvm::OwningArrayRef<char> storage;
auto result = BuildCStrArgs("tool", {}, {}, storage);
llvm::BumpPtrAllocator alloc;
auto result = BuildCStrArgs("tool", {}, {}, alloc);
ASSERT_THAT(result.size(), Eq(1));
EXPECT_THAT(result[0], StrEq("tool"));
}
TEST(BuildCStrArgsWithPrefix, PrefixOnly) {
llvm::OwningArrayRef<char> storage;
llvm::BumpPtrAllocator alloc;
std::string prefix_args[] = {"p_arg1", "p_arg2"};
auto result = BuildCStrArgs("tool", prefix_args, {}, storage);
auto result = BuildCStrArgs("tool", prefix_args, {}, alloc);
ASSERT_THAT(result.size(), Eq(3));
EXPECT_THAT(result[0], StrEq("tool"));
EXPECT_THAT(result[1], Eq(prefix_args[0].c_str()));
@@ -274,8 +275,8 @@ TEST(BuildCStrArgsWithPrefix, PrefixOnly) {
}
TEST(BuildCStrArgsWithPrefix, ArgsOnly) {
llvm::OwningArrayRef<char> storage;
auto result = BuildCStrArgs("tool", {}, {"arg1", "arg2"}, storage);
llvm::BumpPtrAllocator alloc;
auto result = BuildCStrArgs("tool", {}, {"arg1", "arg2"}, alloc);
ASSERT_THAT(result.size(), Eq(3));
EXPECT_THAT(result[0], StrEq("tool"));
EXPECT_THAT(result[1], StrEq("arg1"));
@@ -283,9 +284,9 @@ TEST(BuildCStrArgsWithPrefix, ArgsOnly) {
}
TEST(BuildCStrArgsWithPrefix, BothPrefixAndArgs) {
llvm::OwningArrayRef<char> storage;
llvm::BumpPtrAllocator alloc;
std::string prefix_args[] = {"p_arg1", "p_arg2"};
auto result = BuildCStrArgs("tool", prefix_args, {"arg1", "arg2"}, storage);
auto result = BuildCStrArgs("tool", prefix_args, {"arg1", "arg2"}, alloc);
ASSERT_THAT(result.size(), Eq(5));
EXPECT_THAT(result[0], StrEq("tool"));
EXPECT_THAT(result[1], Eq(prefix_args[0].c_str()));
toolchain/base/clang_invocation.cpp
+2 -2
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@@ -95,9 +95,9 @@ auto BuildClangInvocation(Diagnostics::Consumer& consumer,
// The clang driver inconveniently wants an array of `const char*`, so convert
// the arguments.
llvm::OwningArrayRef<char> cstr_arg_storage;
llvm::BumpPtrAllocator alloc;
llvm::SmallVector<const char*> cstr_args = BuildCStrArgs(
install_paths.clang_path().native(), args, extra_args, cstr_arg_storage);
install_paths.clang_path().native(), args, extra_args, alloc);
// Build a diagnostics engine. Note that we don't have any diagnostic options
// yet; they're produced by running the driver.
toolchain/driver/clang_runner.cpp
+3 -4
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@@ -237,14 +237,13 @@ auto ClangRunner::RunInternal(
std::optional<std::filesystem::path> libunwind_path,
std::optional<std::filesystem::path> libcxx_path, bool enable_leaking)
-> bool {
// Rebuild the args as C-string args.
llvm::OwningArrayRef<char> cstr_arg_storage;
llvm::BumpPtrAllocator alloc;
// Handle special dispatch for CC1 commands as they don't use the driver and
// we don't synthesize any default arguments there.
if (!args.empty() && args[0].starts_with("-cc1")) {
llvm::SmallVector<const char*, 64> cstr_args =
BuildCStrArgs(clang_path_.native(), args, cstr_arg_storage);
BuildCStrArgs(clang_path_.native(), args, alloc);
if (args[0] == "-cc1") {
CARBON_VLOG("Dispatching `-cc1` command line...");
int exit_code =
@@ -297,7 +296,7 @@ auto ClangRunner::RunInternal(
// Rebuild the args as C-string args.
llvm::SmallVector<const char*, 64> cstr_args =
BuildCStrArgs(clang_path_.native(), prefix_args, args, cstr_arg_storage);
BuildCStrArgs(clang_path_.native(), prefix_args, args, alloc);
CARBON_VLOG("Running Clang driver with the following arguments:\n");
for (const char* cstr_arg : llvm::ArrayRef(cstr_args)) {
toolchain/driver/lld_runner.cpp
+3 -2
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@@ -14,6 +14,7 @@
#include "common/vlog.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Allocator.h"
// Declare the supported driver flavor entry points.
//
@@ -33,9 +34,9 @@ auto LldRunner::LinkHelper(llvm::StringLiteral label,
-> bool {
// Allocate one chunk of storage for the actual C-strings and a vector of
// pointers into the storage.
llvm::OwningArrayRef<char> cstr_arg_storage;
llvm::BumpPtrAllocator alloc;
llvm::SmallVector<const char*, 64> cstr_args =
BuildCStrArgs(path, args, cstr_arg_storage);
BuildCStrArgs(path, args, alloc);
CARBON_VLOG("Running LLD {0}-platform link with args:\n", label);
for (const char* cstr_arg : cstr_args) {
toolchain/driver/llvm_runner.cpp
+3 -2
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@@ -15,6 +15,7 @@
#include "lld/Common/Driver.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Allocator.h"
namespace Carbon {
@@ -24,9 +25,9 @@ auto LLVMRunner::Run(LLVMTool tool, llvm::ArrayRef<llvm::StringRef> args)
// Allocate one chunk of storage for the actual C-strings and a vector of
// pointers into the storage.
llvm::OwningArrayRef<char> cstr_arg_storage;
llvm::BumpPtrAllocator alloc;
llvm::SmallVector<const char*, 64> cstr_args =
BuildCStrArgs(path, args, cstr_arg_storage);
BuildCStrArgs(path, args, alloc);
CARBON_VLOG("Running LLVM's {0} tool with args:\n", tool.name());
for (const char* cstr_arg : cstr_args) {