Refactor architecture specific configurations

[jserv]

Instead of #43, I would propose an elegant way to specify the architecture and its configurations. The WIP changes are shown as following:

diff --git a/Makefile b/Makefile
index 9d3e9ca..8a31660 100644
--- a/Makefile
+++ b/Makefile
@@ -20,21 +20,22 @@ OBJS := $(SRCS:%.c=$(OUT)/%.o)
 deps := $(OBJS:%.o=%.o.d)
 TESTS := $(wildcard tests/*.c)
 TESTBINS := $(TESTS:%.c=$(OUT)/%.elf)
-TARGET_EXEC := `cat $(OUT)/target`
 
 all: config bootstrap
 
-config:
-ifeq (riscv,$(ARCH))
-	@$(VECHO) "$(RISCV_EXEC)" > $(OUT)/target
-	@$(VECHO) "#define TARGET_RISCV 1" > $@
-	@ln -s $(PWD)/$(SRCDIR)/riscv-codegen.c $(SRCDIR)/codegen.c
+# set ARM by default
+ifeq ($(strip $(ARCH)),riscv)
+ARCH = riscv
 else
-	@$(VECHO) "$(ARM_EXEC)" > $(OUT)/target
-	@$(VECHO) "#define TARGET_ARM 1" > $@
-	@ln -s $(PWD)/$(SRCDIR)/arm-codegen.c $(SRCDIR)/codegen.c
+ARCH = arm
 endif
-	@$(VECHO) "Target machine code switch to %s\n" "$$(cat out/target | sed 's/.*qemu-\([^ ]*\).*/\1/')"
+
+TARGET_EXEC = $($(shell echo $(ARCH) | tr a-z A-Z)_EXEC)
+
+config:
+	$(Q)ln -s $(PWD)/$(SRCDIR)/$(ARCH)-codegen.c $(SRCDIR)/codegen.c
+	$(call $(ARCH)-specific-defs) > $@
+	$(VECHO) "Target machine code switch to %s\n" $(ARCH)
 
 $(OUT)/tests/%.elf: tests/%.c $(OUT)/$(STAGE0)
 	$(VECHO) "  SHECC\t$@\n"
diff --git a/mk/arm.mk b/mk/arm.mk
index 0195288..5dbddd3 100644
--- a/mk/arm.mk
+++ b/mk/arm.mk
@@ -6,3 +6,10 @@ ARM_EXEC = echo WARN: unable to run
 endif
 
 export ARM_EXEC
+
+arm-specific-defs = \
+    $(Q)$(PRINTF) \
+" \#define ARCH_PREDEFIND \"__arm__\" /* defined by GNU C and RealView */\n\
+  \#define ELF_MACHINE 0x28 /* up to ARMv7/Aarch32 */\n \
+  \#define ELF_FLAGS 0x5000200\n \
+"
diff --git a/mk/riscv.mk b/mk/riscv.mk
index 19fe194..7c0fb62 100644
--- a/mk/riscv.mk
+++ b/mk/riscv.mk
@@ -5,4 +5,11 @@ $(warning "no qemu-riscv32 found. Please check package installation")
 RISCV_EXEC = echo WARN: unable to run
 endif
 
-export RISCV_EXEC
\ No newline at end of file
+export RISCV_EXEC
+
+riscv-specific-defs = \
+    $(Q)$(PRINTF) \
+" \#define ARCH_PREDEFIND \"__riscv\" /* Older versions of the GCC toolchain defined __riscv__ */\n\
+  \#define ELF_MACHINE 0xf3\n\
+  \#define ELF_FLAGS 0\n\
+"
diff --git a/src/cfront.c b/src/cfront.c
index af5f8d6..6da5206 100644
--- a/src/cfront.c
+++ b/src/cfront.c
@@ -2145,15 +2145,8 @@ void parse_internal()
     add_block(NULL, NULL);    /* global block */
     elf_add_symbol("", 0, 0); /* undef symbol */
 
-/* architecture defines */
-/* FIXME: use #ifdef ... #else ... #endif */
-#ifdef TARGET_ARM
-    add_alias("__arm__", "1"); /* defined by GNU C and RealView */
-#endif
-#ifdef TARGET_RISCV
-    /* Older versions of the GCC toolchain defined __riscv__ */
-    add_alias("__riscv", "1");
-#endif
+    /* architecture defines */
+    add_alias(ARCH_PREDEFIND, "1");
 
     /* binary entry point: read params, call main, exit */
     ii = add_instr(OP_label);
diff --git a/src/elf.c b/src/elf.c
index 27bfa12..e266aed 100644
--- a/src/elf.c
+++ b/src/elf.c
@@ -82,13 +82,7 @@ void elf_generate_header()
     elf_write_header_int(0);          /* EI_PAD: unused */
     elf_write_header_byte(2);         /* ET_EXEC */
     elf_write_header_byte(0);
-/* FIXME: use #ifdef ... #else ... #endif */
-#ifdef TARGET_ARM
-    elf_write_header_byte(0x28); /* ARM (up to ARMv7/Aarch32) */
-#endif
-#ifdef TARGET_RISCV
-    elf_write_header_byte(0xf3); /* RISC-V */
-#endif
+    elf_write_header_byte(ELF_MACHINE);
     elf_write_header_byte(0);
     elf_write_header_int(1);                          /* ELF version */
     elf_write_header_int(ELF_START + elf_header_len); /* entry point */
@@ -96,14 +90,7 @@ void elf_generate_header()
     elf_write_header_int(elf_header_len + elf_code_idx + elf_data_idx + 39 +
                          elf_symtab_index +
                          elf_strtab_index); /* section header offset */
-/* flags */
-/* FIXME: use #ifdef ... #else ... #endif */
-#ifdef TARGET_ARM
-    elf_write_header_int(0x5000200); /* ARM */
-#endif
-#ifdef TARGET_RISCV
-    elf_write_header_int(0);
-#endif
+    elf_write_header_int(ELF_FLAGS);
     elf_write_header_byte(0x34); /* header size */
     elf_write_header_byte(0);
     elf_write_header_byte(0x20); /* program header size */

Warning: the patch did not work yet, but it should be fairly expressive.

[eecheng87]

Because the lifetime of $(ARCH), we can't use testing command described in README:

make ARCH=riscv # bootstrap
make check # second pass can't remember value of $ARCH

Instead, we need to change into:

make ARCH=riscv # bootstrap
make ARCH=riscv check

Is this OK? If not, maybe we need some text file to store ARCH.

[jserv]

make config should set and cache the configurations in advance. Therefore, we can specify the target in the first line of config file as following:

/* target: arm */

or

/* target: riscv */

Then, a script in mk directory can read the target from config file. However, once variable ARCH is overridden, the build system should read it. The behavior should be similar to Linux kernel build process.