[Bug ld/17212] Tag_CPU_name merging produces wrong tag for ARM.

[Maxim Ostapenko]

Hi,

I tried to compile a binary optimized for ARM Cortex-A15 with ARM 
Cortex-A8 cross-toolchain (host is x86_64-pc-linux-gnu), but 
Tag_CPU_name appears to be "Cortex-A8" for the binary instead of 
"Cortex-A15". The example session follows:

$ arm-v7a8-linux-gnueabi-gcc -O2 -mcpu=cortex-a15 divtest.c -o divtest.a15

$ readelf -A divtest.a15

Attribute Section: aeabi
File Attributes
Tag_CPU_name: "Cortex-A8"
Tag_CPU_arch: v7
................................................
Tag_DIV_use: Allowed in v7-A with integer division extension

After some investigation I found out, that Tag_CPU_name merging based on 
Tag_CPU_arch. Since the first file to appear during linking is crt1.o, 
which has Tag_CPU_name: "Cortex-A8" for A8 toolchain, the result 
binary's Tag_CPU_name is also "Cortex-A8". Is this expected behavior of 
ld, or maybe tags should be merged to a more specific "Cortex-A15"? 
Perhaps we should use Tag_DIV_use when merging names?

-Maxim