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Run the SSE4.2 span scanners on default x86-64 builds via runtime dispatch #896

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Run the SSE4.2 span scanners on default x86-64 builds via runtime dispatch #896

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12 changes: 12 additions & 0 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,18 @@ set(LLHTTP_SOURCES
${CMAKE_CURRENT_SOURCE_DIR}/src/api.c
)

# On x86-64, compile a second instantiation of the parser with SSE4.2 enabled so
# llhttp_execute() can select it at runtime (see src/api.c). The default build
# passes no -march, so the SSE4.2 span scanners in the generated code are
# otherwise never compiled in. Skipped on MSVC (no __builtin_cpu_supports).
if(NOT MSVC AND CMAKE_SYSTEM_PROCESSOR MATCHES "^(x86_64|amd64|AMD64)$")
list(APPEND LLHTTP_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/src/llhttp_sse42.c)
set_source_files_properties(
${CMAKE_CURRENT_SOURCE_DIR}/src/llhttp_sse42.c
PROPERTIES COMPILE_OPTIONS "-msse4.2"
)
endif()

set(LLHTTP_HEADERS
${CMAKE_CURRENT_SOURCE_DIR}/include/llhttp.h
)
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20 changes: 17 additions & 3 deletions Makefile
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Expand Up @@ -11,6 +11,15 @@ endif

INCLUDES += -Ibuild/

# On x86-64, also build a second instantiation of the generated parser with
# -msse4.2 so llhttp_execute() can select the SSE4.2 span scanners at runtime
# (see src/native/api.c). The default build passes no -march, so without this
# the SSE4.2 code generated under `#ifdef __SSE4_2__` is never compiled in.
ARCH ?= $(shell uname -m)
ifneq (,$(filter $(ARCH),x86_64 amd64 AMD64))
SSE42_OBJ = build/c/llhttp_sse42.o
endif

INSTALL ?= install
PREFIX ?= /usr/local
LIBDIR = $(PREFIX)/lib
Expand All @@ -23,17 +32,20 @@ clean:
rm -rf build/
rm -rf test/tmp

build/libllhttp.so: build/c/llhttp.o build/native/api.o \
build/libllhttp.so: build/c/llhttp.o $(SSE42_OBJ) build/native/api.o \
build/native/http.o
$(CLANG) -shared $^ -o $@

build/libllhttp.a: build/c/llhttp.o build/native/api.o \
build/libllhttp.a: build/c/llhttp.o $(SSE42_OBJ) build/native/api.o \
build/native/http.o
$(AR) rcs $@ build/c/llhttp.o build/native/api.o build/native/http.o
$(AR) rcs $@ build/c/llhttp.o $(SSE42_OBJ) build/native/api.o build/native/http.o

build/c/llhttp.o: build/c/llhttp.c
$(CLANG) $(CFLAGS) $(INCLUDES) -c $< -o $@

build/c/llhttp_sse42.o: build/c/llhttp_sse42.c build/c/llhttp.c
$(CLANG) $(CFLAGS) -msse4.2 $(INCLUDES) -c $< -o $@

build/native/%.o: src/native/%.c build/llhttp.h src/native/api.h \
build/native
$(CLANG) $(CFLAGS) $(INCLUDES) -c $< -o $@
Expand All @@ -52,6 +64,8 @@ release: clean all generate
mkdir -p release/include
cp -rf build/llhttp.h release/include/
cp -rf build/c/llhttp.c release/src/
cp -rf build/c/llhttp_sse42.c release/src/
cp -rf build/c/llhttp_sse42_rename.h release/src/
cp -rf src/native/*.c release/src/
cp -rf src/llhttp.gyp release/
cp -rf src/common.gypi release/
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31 changes: 31 additions & 0 deletions bin/generate.ts
100755 → 100644
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Expand Up @@ -11,6 +11,8 @@ const semverRE = /^(?<major>0|[1-9]\d*)\.(?<minor>0|[1-9]\d*)\.(?<patch>0|[1-9]\

const C_FILE = resolve(__dirname, '../build/c/llhttp.c');
const HEADER_FILE = resolve(__dirname, '../build/llhttp.h');
const SSE42_RENAME_FILE = resolve(__dirname, '../build/c/llhttp_sse42_rename.h');
const SSE42_C_FILE = resolve(__dirname, '../build/c/llhttp_sse42.c');

const pkg = JSON.parse(
readFileSync(resolve(__dirname, '..', 'package.json')).toString(),
Expand Down Expand Up @@ -49,3 +51,32 @@ ${nativeHeaders}
mkdirSync(dirname(C_FILE), { recursive: true });
writeFileSync(HEADER_FILE, headers);
writeFileSync(C_FILE, generated.c);

// A second instantiation of the generated parser, compiled with -msse4.2, lets
// llhttp_execute() use the SSE4.2 span scanners at runtime on default x86-64
// builds (which pass no -march, so the `#ifdef __SSE4_2__` code is otherwise
// dead). The parser defines symbols prefixed `llhttp__internal`; the callbacks
// it imports are prefixed `llhttp__on`/`llhttp__before`/`llhttp__after` and stay
// shared. Rename only the defined `llhttp__internal*` symbols so the second copy
// links beside the first. Derived from the generated source, so it stays correct
// across grammar changes.
const internalSymbols = Array.from(
new Set(generated.c.match(/\bllhttp__internal[0-9A-Za-z_]*/g) ?? []),
).sort();
const renameHeader = `/* Generated by bin/generate.ts. Renames the defined symbols of llhttp.c so a
* second, -msse4.2 instantiation (llhttp_sse42.c) can link beside the first. */
#ifndef INCLUDE_LLHTTP_SSE42_RENAME_H_
#define INCLUDE_LLHTTP_SSE42_RENAME_H_
${internalSymbols.map((s) => `#define ${s} ${s}_sse42`).join('\n')}
#endif /* INCLUDE_LLHTTP_SSE42_RENAME_H_ */
`;
const sse42Wrapper = `/* Generated by bin/generate.ts. See src/native/api.c: a second instantiation of
* the generated parser with the SSE4.2 span scanners enabled, selected once at
* runtime by llhttp_execute(). Built with -msse4.2 by the build system. */
#if defined(__x86_64__) || defined(_M_X64)
#include "llhttp_sse42_rename.h"
#include "llhttp.c"
#endif
`;
writeFileSync(SSE42_RENAME_FILE, renameHeader);
writeFileSync(SSE42_C_FILE, sse42Wrapper);
24 changes: 24 additions & 0 deletions src/native/api.c
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Expand Up @@ -122,9 +122,33 @@ void llhttp_reset(llhttp_t* parser) {
}


#if (defined(__x86_64__) || defined(_M_X64)) && !defined(__SSE4_2__) && \
(defined(__GNUC__) || defined(__clang__))
/* A second instantiation of the generated parser, compiled with -msse4.2 (see
* llhttp_sse42.c), which turns on the SSE4.2 span scanners that the generated
* code guards with `#ifdef __SSE4_2__`. The default x86-64 build (no -march)
* never contains them, so pick the SSE4.2 build once at runtime. Both
* instantiations come from the same generated source, so the parser state
* layout is identical and a parser may be driven by either. */
llhttp_errno_t llhttp__internal_execute_sse42(llhttp_t* state, const char* p,
const char* endp);

static int llhttp__sse42 = -1;

llhttp_errno_t llhttp_execute(llhttp_t* parser, const char* data, size_t len) {
if (llhttp__sse42 < 0) {
llhttp__sse42 = __builtin_cpu_supports("sse4.2") ? 1 : 0;
}
if (llhttp__sse42) {
return llhttp__internal_execute_sse42(parser, data, data + len);
}
return llhttp__internal_execute(parser, data, data + len);
}
#else
llhttp_errno_t llhttp_execute(llhttp_t* parser, const char* data, size_t len) {
return llhttp__internal_execute(parser, data, data + len);
}
#endif


void llhttp_settings_init(llhttp_settings_t* settings) {
Expand Down