On Fri, Aug 6, 2021 at 3:40 AM Nick Desaulniers [off-list ref] wrote:

On Thu, Aug 5, 2021 at 8:16 AM Masahiro Yamada [off-list ref] wrote:

quoted

On Tue, Aug 3, 2021 at 8:43 AM Nick Desaulniers [off-list ref] wrote:

quoted

diff --git a/Makefile b/Makefile
index 444558e62cbc..b24b48c9ebb7 100644
--- a/Makefile
+++ b/Makefile

@@ -845,7 +845,7 @@ else
 DEBUG_CFLAGS   += -g
 endif

-ifneq ($(LLVM_IAS),1)
+ifeq ($(LLVM_IAS),0)
 KBUILD_AFLAGS  += -Wa,-gdwarf-2
 endif

diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index bc74afdbf31e..807f7c94bc6f 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile

@@ -41,7 +41,7 @@ endif
 ifeq ($(CONFIG_LD_IS_LLD),y)
        KBUILD_CFLAGS += -mno-relax
        KBUILD_AFLAGS += -mno-relax
-ifneq ($(LLVM_IAS),1)
+ifeq ($(LLVM_IAS),0)
        KBUILD_CFLAGS += -Wa,-mno-relax
        KBUILD_AFLAGS += -Wa,-mno-relax
 endif

Please drop these two hunks.

I will apply my patch instead.
https://lore.kernel.org/patchwork/patch/1472580/

Sure.  Will send a v2 with Matthew's suggestion as well.

quoted

When we negate a flag that is enabled by default,
which is a common way?
 - set it to '0'
 - set is to empty


So, I was wondering if we should support
not only LLVM_IAS=0 but also LLVM_IAS=.

What do you think?

LLVM_IAS= looks weird (so I agree with Khem's response), but if it's
common/expected then maybe if there's a way to write a concise check
for either =<blank> or =0?  I don't feel strongly about how it's
specified to disable the integrated assembler, but let's sort that out
_before_ I send a v2.

How can you tell the difference between `make CC=clang` and `make
CC=clang LLVM_IAS=`? (maybe that doesn't matter here, as either imply
"don't use clang as the assembler when compiling with clang")

$(origin LLVM_IAS) knows the difference.

make CC=clang            ->  $(origin LLVM_IAS) is 'undefined'
make CC=clang LLVM_IAS=  ->  $(origin LLVM_IAS) is 'command line'
LLVM_IAS= make CC=clang  ->  $(origin LLVM_IAS) is 'environment'




The following patch makes both LLVM_IAS= and LLVM_IAS=0
work for disabling the integrated assembler.

@@ -22,6 +22,9 @@ else
 CLANG_FLAGS    += --target=$(notdir $(CROSS_COMPILE:%-=%))
 endif # CROSS_COMPILE

+# The integrated assembler is enabled by default.
+LLVM_IAS ?= 1
+
 ifeq ($(LLVM_IAS),1)
 CLANG_FLAGS    += -integrated-as
 else

But, I am not pretty sure if it is a good idea...

Perhaps, it is better to require LLVM_IAS=0
as Khem mentioned.


Another way for avoiding ambiguity is, perhaps
LLVM_IAS_DISABLE=1 instead of LLVM_IAS=0.


-- 
Best Regards
Masahiro Yamada