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Re: [Minios-devel] [UNIKRAFT PATCHv5 22/46] arch/arm64: Avoid using the floating-point and Advanced SIMD registers



Hi,

On 10.08.2018 09:08, Wei Chen wrote:
From: Wei Chen <Wei.Chen@xxxxxxx>

On Arm64, sometimes, the GCC will use floating-point and Advanced
SIMD registers to pass parameters. For example, the va_list will
use the SIMD&FP registers (like q0, q1) to store parameters, no
matter you are using floating-point or not.

So, we use the GCC -mgeneral-regs-only flag to force GCC to use
generic registers only util the floating-point and Advanced SIMD
registers are required actually.

Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
---
  arch/arm/arm64/Makefile.uk | 6 +++---
  1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm/arm64/Makefile.uk b/arch/arm/arm64/Makefile.uk
index d4ba7e3..82a159f 100644
--- a/arch/arm/arm64/Makefile.uk
+++ b/arch/arm/arm64/Makefile.uk
@@ -1,6 +1,6 @@
-ASFLAGS  += -D__ARM_64__
-CFLAGS   += -D__ARM_64__ -fms-extensions
-CXXFLAGS += -D__ARM_64__ -fms-extensions
+ASFLAGS  += -D__ARM_64__ -mgeneral-regs-only
+CFLAGS   += -D__ARM_64__ -fms-extensions -mgeneral-regs-only
+CXXFLAGS += -D__ARM_64__ -fms-extensions -mgeneral-regs-only

Could you maybe also add a short TODO comment and explain that we are using non-floating point for now.
Other form this, this patch is fine ;-)

# GCC support -mcpu=native for arm64 from 6.0
  ifeq ($(CONFIG_MARCH_ARM64_NATIVE),y)


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