[PATCH 2/2] Makefile: Don't enable V-extension using -march option

[Jessica Clarke]

On 10 Dec 2024, at 04:16, Anup Patel <apatel at ventanamicro.com> wrote:
> 
> Enabling V-extension using -march option causes OpenSBI boot-time
> hang with LLVM compiler.
> 
> As a work-around, don't enable V-extension using -march option and
> instead use a custom OpenSBI specific define inform availability of
> V-extension to lib/sbi/sbi_trap_v_ldst.c.
> 
> Fixes: c2acc5e5b0d8 ("lib: sbi_misaligned_ldst: Add handling of vector load/store")
> Signed-off-by: Anup Patel <apatel at ventanamicro.com>
> ---
> Makefile                  | 8 ++++----
> lib/sbi/sbi_trap_v_ldst.c | 5 +++--
> 2 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 5ac95a0f..7e0a1399 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -190,7 +190,7 @@ CC_SUPPORT_STRICT_ALIGN := $(shell $(CC) $(CLANG_TARGET) $(RELAX_FLAG) -nostdlib
> CC_SUPPORT_ZICSR_ZIFENCEI := $(shell $(CC) $(CLANG_TARGET) $(RELAX_FLAG) -nostdlib -march=rv$(OPENSBI_CC_XLEN)imafd_zicsr_zifencei -x c /dev/null -o /dev/null 2>&1 | grep -e "zicsr" -e "zifencei" > /dev/null && echo n || echo y)
> 
> # Check whether the assembler and the compiler support the Vector extension
> -CC_SUPPORT_VECT := $(shell echo | $(CC) -dM -E -march=rv$(OPENSBI_CC_XLEN)gv - | grep -q riscv.*vector && echo y || echo n)
> +CC_SUPPORT_VECT := $(shell $(CC) $(CLANG_TARGET) $(RELAX_FLAG) -nostdlib -march=rv$(OPENSBI_CC_XLEN)gv -dM -E -x c /dev/null 2>&1 | grep -q riscv.*vector && echo y || echo n)
> 
> ifneq ($(OPENSBI_LD_PIE),y)
> $(error Your linker does not support creating PIEs, opensbi requires this.)
> @@ -298,9 +298,6 @@ endif
> ifndef PLATFORM_RISCV_ISA
>   ifneq ($(PLATFORM_RISCV_TOOLCHAIN_DEFAULT), 1)
>     PLATFORM_RISCV_ISA := rv$(PLATFORM_RISCV_XLEN)imafdc
> -    ifeq ($(CC_SUPPORT_VECT), y)
> -      PLATFORM_RISCV_ISA := $(PLATFORM_RISCV_ISA)v
> -    endif
>     ifeq ($(CC_SUPPORT_ZICSR_ZIFENCEI), y)
>       PLATFORM_RISCV_ISA := $(PLATFORM_RISCV_ISA)_zicsr_zifencei
>     endif
> @@ -363,6 +360,9 @@ GENFLAGS += $(firmware-genflags-y)
> CFLAGS = -g -Wall -Werror -ffreestanding -nostdlib -fno-stack-protector -fno-strict-aliasing -ffunction-sections -fdata-sections
> CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
> # Optionally supported flags
> +ifeq ($(CC_SUPPORT_VECT),y)
> +CFLAGS += -DOPENSBI_CC_SUPPORT_VECT -fno-tree-vectorize

The latter isn’t needed now you don’t enable V. Clang ignores it, even,
it’s a flag that’s tied to GCC’s internals.

Jess