On Fri, Nov 03, 2017 at 10:53:08AM -0700, Nick Desaulniers wrote:

These mrs_s and msr_s macros in particular were preventing us from
linking arm64 with Clang's integrated assembler, regardless of LTO.
Those macros ran into: https://bugs.llvm.org/show_bug.cgi?id=19749.
So while I appreciate how clever they are, they prevent us from
assembling with Clang so I would like to see them go.

They're necessary to work with some currently-supported toolchains
(which don't support the s*_*_c*_c*_* syntax), so they're not going to
go completely.

If you could suggest something that clang might prefer, which doesn't
adversely affect GCC, I'm all ears.

Thanks,
Mark.

On Fri, Nov 3, 2017 at 10:12 AM, Sami Tolvanen [off-list ref] wrote:

quoted

Clang's integrated assembler does not allow assembly macros defined
in one inline asm block using the .macro directive to be used across
separate asm blocks. LLVM developers consider this a feature and not a
bug, recommending code refactoring:

  https://bugs.llvm.org/show_bug.cgi?id=19749

As binutils doesn't allow macros to be redefined, this change adds C
preprocessor macros that define the assembly macros globally for binutils
and locally for clang's integrated assembler.

Suggested-by: Greg Hackmann <redacted>
Suggested-by: Nick Desaulniers <redacted>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 arch/arm64/include/asm/kvm_hyp.h |  2 ++
 arch/arm64/include/asm/sysreg.h  | 71 ++++++++++++++++++++++++++++++----------
 2 files changed, 56 insertions(+), 17 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
index 4572a9b560fa..6840704ea894 100644
--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h

@@ -29,6 +29,7 @@
        ({                                                              \
                u64 reg;                                                \
                asm volatile(ALTERNATIVE("mrs %0, " __stringify(r##nvh),\
+                                        DEFINE_MRS_S                   \
                                         "mrs_s %0, " __stringify(r##vh),\
                                         ARM64_HAS_VIRT_HOST_EXTN)      \
                             : "=r" (reg));                             \

@@ -39,6 +40,7 @@
        do {                                                            \
                u64 __val = (u64)(v);                                   \
                asm volatile(ALTERNATIVE("msr " __stringify(r##nvh) ", %x0",\
+                                        DEFINE_MSR_S                   \
                                         "msr_s " __stringify(r##vh) ", %x0",\
                                         ARM64_HAS_VIRT_HOST_EXTN)      \
                                         : : "rZ" (__val));             \

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index f707fed5886f..1588ac3f3690 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h

@@ -463,21 +463,58 @@

 #include <linux/types.h>

-asm(
-"      .irp    num,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30\n"
-"      .equ    .L__reg_num_x\\num, \\num\n"
-"      .endr\n"
+#define ___MRS_MSR_S_REGNUM                                    \
+"      .irp    num,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30\n" \
+"      .equ    .L__reg_num_x\\num, \\num\n"                    \
+"      .endr\n"                                                \
 "      .equ    .L__reg_num_xzr, 31\n"
-"\n"
-"      .macro  mrs_s, rt, sreg\n"
-       __emit_inst(0xd5200000|(\\sreg)|(.L__reg_num_\\rt))
+
+#define ___MRS_S                                               \
+"      .macro  mrs_s, rt, sreg\n"                              \
+       __emit_inst(0xd5200000|(\\sreg)|(.L__reg_num_\\rt))     \
 "      .endm\n"
-"\n"
-"      .macro  msr_s, sreg, rt\n"
-       __emit_inst(0xd5000000|(\\sreg)|(.L__reg_num_\\rt))
+
+#define ___MSR_S                                               \
+"      .macro  msr_s, sreg, rt\n"                              \
+       __emit_inst(0xd5000000|(\\sreg)|(.L__reg_num_\\rt))     \
 "      .endm\n"
+
+/*
+ * llvm-as doesn't allow macros defined in an asm block to be used in other
+ * asm blocks, which means we cannot define them globally.
+ */
+#if !defined(CONFIG_CLANG_LTO)
+asm(
+       ___MRS_MSR_S_REGNUM
+       ___MRS_S
+       ___MSR_S
 );

+#undef  ___MRS_MSR_S_REGNUM
+#define ___MRS_MSR_S_REGNUM
+#undef  ___MRS_S
+#define ___MRS_S
+#undef  ___MSR_S
+#define ___MSR_S
+#endif
+
+#define DEFINE_MRS_S           \
+       ___MRS_MSR_S_REGNUM     \
+       ___MRS_S
+
+#define DEFINE_MSR_S           \
+       ___MRS_MSR_S_REGNUM     \
+       ___MSR_S
+
+
+#define __mrs_s(r, v)                                          \
+       DEFINE_MRS_S                                            \
+"      mrs_s %0, " __stringify(r) : "=r" (v)
+
+#define __msr_s(r, v)                                          \
+       DEFINE_MSR_S                                            \
+"      msr_s " __stringify(r) ", %0" : : "r" (v)
+
 /*
  * Unlike read_cpuid, calls to read_sysreg are never expected to be
  * optimized away or replaced with synthetic values.

@@ -502,15 +539,15 @@ asm(
  * For registers without architectural names, or simply unsupported by
  * GAS.
  */
-#define read_sysreg_s(r) ({                                            \
-       u64 __val;                                                      \
-       asm volatile("mrs_s %0, " __stringify(r) : "=r" (__val));       \
-       __val;                                                          \
+#define read_sysreg_s(r) ({                                    \
+       u64 __val;                                              \
+       asm volatile(__mrs_s(r, __val));                        \
+       __val;                                                  \
 })

-#define write_sysreg_s(v, r) do {                                      \
-       u64 __val = (u64)(v);                                           \
-       asm volatile("msr_s " __stringify(r) ", %x0" : : "rZ" (__val)); \
+#define write_sysreg_s(v, r) do {                              \
+       u64 __val = (u64)(v);                                   \
+       asm volatile(__msr_s(r, __val));                        \
 } while (0)

 static inline void config_sctlr_el1(u32 clear, u32 set)
--

2.15.0.403.gc27cc4dac6-goog

-- 
Thanks,
~Nick Desaulniers

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