[PATCH] Makefile: Avoid repeated evaluation of shell commands

[Xiang W]

在 2025-03-12三的 20:57 -0700，Samuel Holland写道：
> Recursively expanded variables (defined with '=') are expanded at
> evaluation time. These version information variables are evaluated
> inside a recipe as part of GENFLAGS. As a result, the shell commands
> are executed separately for each compiler invocation. Convert the
> version information variables to be simply expanded, so the shell
> commands are executed only once, at Makefile evaluation time. This
> speeds up the build by as much as 75%.
> 
> A separate check is needed to maintain the behavior of preferring the
> value of OPENSBI_BUILD_TIME_STAMP from the environment.
> 
> Signed-off-by: Samuel Holland <samuel.holland at sifive.com>
LGTM

Reviewed-by: Xiang W <wxjstz at 126.com>
> ---
> 
>  Makefile | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 419ce66b..c1a13037 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -94,11 +94,11 @@ OPENSBI_VERSION_MINOR=`grep "define OPENSBI_VERSION_MINOR" $(include_dir)/sbi/sb
>  OPENSBI_VERSION_GIT=
>  
>  # Detect 'git' presence before issuing 'git' commands
> -GIT_AVAIL=$(shell command -v git 2> /dev/null)
> +GIT_AVAIL := $(shell command -v git 2> /dev/null)
>  ifneq ($(GIT_AVAIL),)
> -GIT_DIR=$(shell git rev-parse --git-dir 2> /dev/null)
> +GIT_DIR := $(shell git rev-parse --git-dir 2> /dev/null)
>  ifneq ($(GIT_DIR),)
> -OPENSBI_VERSION_GIT=$(shell if [ -d $(GIT_DIR) ]; then git describe 2> /dev/null; fi)
> +OPENSBI_VERSION_GIT := $(shell if [ -d $(GIT_DIR) ]; then git describe 2> /dev/null; fi)
>  endif
>  endif
>  
> @@ -202,16 +202,18 @@ endif
>  BUILD_INFO ?= n
>  ifeq ($(BUILD_INFO),y)
>  OPENSBI_BUILD_DATE_FMT = +%Y-%m-%d %H:%M:%S %z
> +ifndef OPENSBI_BUILD_TIME_STAMP
>  ifdef SOURCE_DATE_EPOCH
> -	OPENSBI_BUILD_TIME_STAMP ?= $(shell date -u -d "@$(SOURCE_DATE_EPOCH)" \
> +	OPENSBI_BUILD_TIME_STAMP := $(shell date -u -d "@$(SOURCE_DATE_EPOCH)" \
>  		"$(OPENSBI_BUILD_DATE_FMT)" 2>/dev/null || \
>  		date -u -r "$(SOURCE_DATE_EPOCH)" \
>  		"$(OPENSBI_BUILD_DATE_FMT)" 2>/dev/null || \
>  		date -u "$(OPENSBI_BUILD_DATE_FMT)")
>  else
> -	OPENSBI_BUILD_TIME_STAMP ?= $(shell date "$(OPENSBI_BUILD_DATE_FMT)")
> +	OPENSBI_BUILD_TIME_STAMP := $(shell date "$(OPENSBI_BUILD_DATE_FMT)")
>  endif
> -OPENSBI_BUILD_COMPILER_VERSION=$(shell $(CC) -v 2>&1 | grep ' version ' | \
> +endif
> +OPENSBI_BUILD_COMPILER_VERSION := $(shell $(CC) -v 2>&1 | grep ' version ' | \
>  	sed 's/[[:space:]]*$$//')
>  endif
>  
> -- 
> 2.47.2
>