Makefile: don't pass -mstrict-align if not supported

Support for that option will be added in LLVM 18:
https://github.com/llvm/llvm-project/commit/23ce5368409c760f3dd49d0f17f34772b0b869d8

Clang 17.0.6, however, will error when passed the
`-mstrict-align` flag.
We should only use the flag if it is supported.

Signed-off-by: Kalle Wachsmuth <kalle.wachsmuth@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Xiang W <wxjstz@126.com>

diff --git a/Makefile b/Makefile
index de4e73a0e3d830d235fc59f0a5e5afb9a5d4503f..66048c38acb8a269a49589bbd6d41a3c7a415b6e 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -170,6 +170,9 @@ OPENSBI_LD_PIE := $(shell $(CC) $(CLANG_TARGET) $(RELAX_FLAG) $(USE_LD_FLAG) -fP
 # Check whether the compiler supports -m(no-)save-restore
 CC_SUPPORT_SAVE_RESTORE := $(shell $(CC) $(CLANG_TARGET) $(RELAX_FLAG) -nostdlib -mno-save-restore -x c /dev/null -o /dev/null 2>&1 | grep -e "-save-restore" >/dev/null && echo n || echo y)
 
+# Check whether the compiler supports -m(no-)strict-align
+CC_SUPPORT_STRICT_ALIGN := $(shell $(CC) $(CLANG_TARGET) $(RELAX_FLAG) -nostdlib -mstrict-align -x c /dev/null -o /dev/null 2>&1 | grep -e "-mstrict-align\|-mno-unaligned-access" >/dev/null && echo n || echo y)
+
 # Check whether the assembler and the compiler support the Zicsr and Zifencei extensions
 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 "zicsr\|zifencei" > /dev/null && echo n || echo y)
 
@@ -337,11 +340,14 @@ CFLAGS            +=      -O0
 else
 CFLAGS         +=      -O2
 endif
-CFLAGS         +=      -fno-omit-frame-pointer -fno-optimize-sibling-calls -mstrict-align
-# enable -m(no-)save-restore option by CC_SUPPORT_SAVE_RESTORE
+CFLAGS         +=      -fno-omit-frame-pointer -fno-optimize-sibling-calls
+# Optionally supported flags
 ifeq ($(CC_SUPPORT_SAVE_RESTORE),y)
 CFLAGS         +=      -mno-save-restore
 endif
+ifeq ($(CC_SUPPORT_STRICT_ALIGN),y)
+CFLAGS         +=      -mstrict-align
+endif
 CFLAGS         +=      -mabi=$(PLATFORM_RISCV_ABI) -march=$(PLATFORM_RISCV_ISA)
 CFLAGS         +=      -mcmodel=$(PLATFORM_RISCV_CODE_MODEL)
 CFLAGS         +=      $(RELAX_FLAG)
@@ -355,11 +361,14 @@ CPPFLAGS  +=      $(platform-cppflags-y)
 CPPFLAGS       +=      $(firmware-cppflags-y)
 
 ASFLAGS                =       -g -Wall -nostdlib
-ASFLAGS                +=      -fno-omit-frame-pointer -fno-optimize-sibling-calls -mstrict-align
-# enable -m(no-)save-restore option by CC_SUPPORT_SAVE_RESTORE
+ASFLAGS                +=      -fno-omit-frame-pointer -fno-optimize-sibling-calls
+# Optionally supported flags
 ifeq ($(CC_SUPPORT_SAVE_RESTORE),y)
 ASFLAGS                +=      -mno-save-restore
 endif
+ifeq ($(CC_SUPPORT_STRICT_ALIGN),y)
+ASFLAGS                +=      -mstrict-align
+endif
 ASFLAGS                +=      -mabi=$(PLATFORM_RISCV_ABI) -march=$(PLATFORM_RISCV_ISA)
 ASFLAGS                +=      -mcmodel=$(PLATFORM_RISCV_CODE_MODEL)
 ASFLAGS                +=      $(RELAX_FLAG)