From 0eb9265fe737d901f484e4bcd73ffe386eb35693 Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Tue, 13 Feb 2024 14:26:48 -0500 Subject: [PATCH] c++/modules: use optimized crc32 from zlib The current implementation of bytes::calc_crc computes the checksum one byte at a time which turns out to be quite slow, accounting for 15% of streaming in time for a modular Hello World. We have a crc32_unsigned version that processes 4 bytes at a time which we could use here, but since we bundle zlib we might as well use its highly optimized crc routines that can process up to 32 bytes at a time. So this patch makes us use zlib's crc32 in this hot code path. This reduces stream in time for a modular Hello World by around 15% for me with a release compiler. gcc/cp/ChangeLog: * Make-lang.in (CFLAGS-cp/module.o): Add $(ZLIBINC). * module.cc: Include . (bytes::calc_crc): Use crc32 from zlib. (bytes_out::set_crc): Use crc32_combine from zlib. Reviewed-by: Jason Merill --- gcc/cp/Make-lang.in | 2 +- gcc/cp/module.cc | 8 +++----- 2 files changed, 4 insertions(+), 6 deletions(-) diff --git a/gcc/cp/Make-lang.in b/gcc/cp/Make-lang.in index 630db41d87e..f153891a1ef 100644 --- a/gcc/cp/Make-lang.in +++ b/gcc/cp/Make-lang.in @@ -55,7 +55,7 @@ c++.serial = cc1plus$(exeext) CFLAGS-cp/g++spec.o += $(DRIVER_DEFINES) CFLAGS-cp/module.o += -DHOST_MACHINE=\"$(host)\" \ - -DTARGET_MACHINE=\"$(target)\" + -DTARGET_MACHINE=\"$(target)\" $(ZLIBINC) # In non-release builds, use a date-related module version. ifneq ($(DEVPHASE_c),) diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc index 34fafe7c978..0291d456ff5 100644 --- a/gcc/cp/module.cc +++ b/gcc/cp/module.cc @@ -233,6 +233,7 @@ Classes used: /* This TU doesn't need or want to see the networking. */ #define CODY_NETWORKING 0 #include "mapper-client.h" +#include // for crc32, crc32_combine #if 0 // 1 for testing no mmap #define MAPPED_READING 0 @@ -487,10 +488,7 @@ protected: unsigned bytes::calc_crc (unsigned l) const { - unsigned crc = 0; - for (size_t ix = 4; ix < l; ix++) - crc = crc32_byte (crc, buffer[ix]); - return crc; + return crc32 (0, (unsigned char *)buffer + 4, l - 4); } class elf_in; @@ -717,7 +715,7 @@ bytes_out::set_crc (unsigned *crc_ptr) unsigned crc = calc_crc (pos); unsigned accum = *crc_ptr; /* Only mix the existing *CRC_PTR if it is non-zero. */ - accum = accum ? crc32_unsigned (accum, crc) : crc; + accum = accum ? crc32_combine (accum, crc, pos - 4) : crc; *crc_ptr = accum; /* Buffer will be sufficiently aligned. */