[PATCH 1/1] Makefile: Speed up parallel build

[Anup Patel]

On Thu, Sep 24, 2026 at 11:32 AM Maxim Kochetkov <fido_max at inbox.ru> wrote:
>
> Parallel build is extremely slow when using vars (O, I,
> PLATFORM_DIR+PLATFORM). And all this is because the variables are
> calculated continuously, with the simultaneous invocation of
> the $(shell ...). So use "Simply expanded variables" to
> calculate value and call $(shell ...) just once.
>
> Signed-off-by: Maxim Kochetkov <fido_max at inbox.ru>

LGMT.

Reviewed-by: Anup Patel <anup at brainfault.org>

Applied this patch to the riscv/opensbi repo.

Thanks,
Anup


> ---
>  Makefile | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 1b3333f3..da6751fd 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -22,18 +22,18 @@ endif
>  # Find out source, build, and install directories
>  src_dir=$(CURDIR)
>  ifdef O
> - build_dir=$(shell $(READLINK) -f $(O))
> + build_dir:=$(shell $(READLINK) -f $(O))
>  else
> - build_dir=$(CURDIR)/build
> + build_dir:=$(CURDIR)/build
>  endif
>  ifeq ($(build_dir),$(CURDIR))
>  $(error Build directory is same as source directory.)
>  endif
>  install_root_dir_default=$(CURDIR)/install
>  ifdef I
> - install_root_dir=$(shell $(READLINK) -f $(I))
> + install_root_dir:=$(shell $(READLINK) -f $(I))
>  else
> - install_root_dir=$(install_root_dir_default)/usr
> + install_root_dir:=$(install_root_dir_default)/usr
>  endif
>  ifeq ($(install_root_dir),$(CURDIR))
>  $(error Install root directory is same as source directory.)
> @@ -42,12 +42,12 @@ ifeq ($(install_root_dir),$(build_dir))
>  $(error Install root directory is same as build directory.)
>  endif
>  ifdef PLATFORM_DIR
> -  platform_dir_path=$(shell $(READLINK) -f $(PLATFORM_DIR))
> +  platform_dir_path:=$(shell $(READLINK) -f $(PLATFORM_DIR))
>    ifdef PLATFORM
>      platform_parent_dir=$(platform_dir_path)
>    else
> -    PLATFORM=$(shell basename $(platform_dir_path))
> -    platform_parent_dir=$(shell realpath ${platform_dir_path}/..)
> +    PLATFORM:=$(shell basename $(platform_dir_path))
> +    platform_parent_dir:=$(shell realpath ${platform_dir_path}/..)
>    endif
>  else
>   platform_parent_dir=$(src_dir)/platform
> --
> 2.55.0
>
>
> --
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