powerpc: Introduce and enforce assembler checks on GPR usage
PowerPC general-purpose registers are historically specified as plain
numbers (0-31), which makes them hard to distinguish from immediates.
For this reason, include/ppc_asm.tmpl defines aliases named r0-r31.
This can still lead to uncaught mistakes if a register is used in place
of a number.
Instead of (e.g.) 5 use %r5, which will result in an assembler warning
if used as a number. Turn these warnings into errors by passing
`--fatal-warnings` to the assembler.
I verified with gazerbeam_defconfig (MPC83xx) and qemu-ppce500_defconfig
(MPC85xx) that this patch results in the same machine code.
Signed-off-by: J. Neuschäfer <j.ne@posteo.net>
diff --git a/arch/powerpc/config.mk b/arch/powerpc/config.mk
index dd0124c..6e30df6 100644
--- a/arch/powerpc/config.mk
+++ b/arch/powerpc/config.mk
@@ -8,7 +8,7 @@
PLATFORM_RELFLAGS += -fpic -mrelocatable -ffunction-sections \
-fdata-sections -mcall-linux
-PF_CPPFLAGS_POWERPC := $(call cc-option,-fno-ira-hoist-pressure,)
+PF_CPPFLAGS_POWERPC := $(call cc-option,-fno-ira-hoist-pressure,) $(call cc-option,-Xassembler --fatal-warnings,)
PLATFORM_CPPFLAGS += -D__powerpc__ -ffixed-r2 -m32 $(PF_CPPFLAGS_POWERPC)
KBUILD_LDFLAGS += -m32 -melf32ppclinux