I did some code density comparisons for a gemlog post I was writing. This is just the size of the buildroot-generated busybox binary, across every buildroot-supported target except CSky, with a preference for "typical" embedded configs when possible and with -Os as the optimization flag. I thought folks here might find it at least a little interesting.

• ARC LE - 623,912 bytes - 8K pages, HS38 Quad MAC + FPU target
  
• ARM Thumb2 LE - 599,248 bytes - Thumb2, VFPv4-D16, Cortex-A7 target
  
• ARM64 LE - 779,936 bytes - Cortex-A76 target, FP-ARMv8
  
• x86 - 713,916 bytes - i686 target
  
• m68k - 698,776 bytes - M68040 target
  
• Microblaze LE - 1,223,148 bytes - No target specific settings available
  
• MIPS32 LE - 1,017,196 bytes - P5600 target, no softfloat
  
• MIPS64 LE - 989,024 bytes - P6600 target, no softfloat, n32 ABI
  
• NDS32 - 888,124 bytes - No target specific settings available
  
• Nios II - 892,316 bytes - No target specific settings available
  
• OpenRISC - 1,133,164 bytes - No target specific settings available
  
• PPC32 - 984,396 bytes - 476FP target
  
• PPC64LE - 985,552 bytes - Power8 target
  
• RV64GC - 741,856 bytes - ilp64d ABI
  
• RV32GC - 719,916 bytes - ilp32d ABI
  
• S390X - 907,712 bytes - z15 target
  
• SH-4A LE - 842,884 bytes - No target specific settings
  
• SPARC32 - 931,064 bytes - generic SPARCv8
  
• SPARC64 - 997,624 bytes - generic SPARCv9
  
• x86_64 - 747,224 bytes - Haswell target
  
• Xtensa - 1,216,228 bytes - fsf target
  

Feel free to criticize my methodology! I don't pretend this is super scientific, but I thought it was an interesting data point.