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我想为armv6构建libx264,但是我得到的似乎是为armv7构建的。我使用这个配置行:为什么即使我设置了-march = armv6,为armv7构建的库?
./configure --host=arm-linux-gnueabihf --enable-static --cross-prefix=${CCPREFIX} --prefix=... --extra-cflags='-march=armv6' --extra-ldflags='-march=armv6' --extra-asflags='-march=armv6'
导致像这样的输出:
[...]
arm-linux-gnueabihf-gcc -Wno-maybe-uninitialized -Wshadow -O3 -ffast-math -Wall -I. -I. -march=armv6 -std=gnu99 -D_GNU_SOURCE -fomit-frame-pointer -fno-tree-vectorize -c -o common/opencl.o common/opencl.c
arm-linux-gnueabihf-gcc -Wno-maybe-uninitialized -Wshadow -O3 -ffast-math -Wall -I. -I. -march=armv6 -std=gnu99 -D_GNU_SOURCE -fomit-frame-pointer -fno-tree-vectorize -c -o encoder/slicetype-cl.o encoder/slicetype-cl.c
arm-linux-gnueabihf-gcc -I. -I. -march=armv6 -c -DSTACK_ALIGNMENT=4 -DHIGH_BIT_DEPTH=0 -DBIT_DEPTH=8 -o common/arm/cpu-a.o common/arm/cpu-a.S
[...]
现在这是我所看到的:
$ readelf -A x264
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "7-A"
Tag_CPU_arch: v7
Tag_CPU_arch_profile: Application
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-2
Tag_FP_arch: VFPv3
Tag_Advanced_SIMD_arch: NEONv1
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align_needed: 8-byte
Tag_ABI_enum_size: int
Tag_ABI_HardFP_use: Deprecated
Tag_ABI_VFP_args: VFP registers
Tag_CPU_unaligned_access: v6
Tag_DIV_use: Not allowed
我也看到这一点:
$ readelf -A encoder/slicetype-cl.o
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "6"
Tag_CPU_arch: v6
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-1
Tag_FP_arch: VFPv2
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_number_model: Finite
Tag_ABI_align_needed: 8-byte
Tag_ABI_align_preserved: 8-byte, except leaf SP
Tag_ABI_enum_size: int
Tag_ABI_HardFP_use: Deprecated
Tag_ABI_VFP_args: VFP registers
Tag_ABI_optimization_goals: Aggressive Speed
Tag_CPU_unaligned_access: v6
但是:
$ readelf -A common/arm/cpu-a.o
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "7-A"
Tag_CPU_arch: v7
Tag_CPU_arch_profile: Application
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-2
Tag_FP_arch: VFPv3
Tag_Advanced_SIMD_arch: NEONv1
有人可以解释为什么这些命令似乎输出armv6二进制一次,但在另一种情况下,armv7二进制?这可能是为什么生成的二进制文件被标记为armv7的原因? 谢谢你的任何解释。
所以我猜汇编器会自动选择armv7而不是armv6吗?这意味着可能armv6完全不受该代码的支持。实际上,我只是发现了一个--disable-asm选项,它可能在这种情况下使用。结果现在是armv6。谢谢! –