Sudden compile error: "unable to find a register to spill in class 'NO_REGS'"

Hi folks,

I am refactoring existing code, which until this point compiled fine. I didn't add any new libraries or functionality. Suddenly, compilation fails with a long, drawn out series of errors. I don't understand what caused this or what to do. Have I reached some point of critical mass? Too many variables? Source file too long?

In my investigation, I uploaded my sketch to the Arduino Web Compiler and I get a similar error. Something is wrong, I don't know what, and I would greatly appreciate your help!

Thanks,
Mike

PS Here is the compilation output:

Arduino: 1.8.3 (Mac OS X), Board: "Arduino/Genuino Uno"

/Users/Mike/Library/Arduino15/packages/arduino/hardware/avr/1.6.19/cores/arduino/main.cpp: In function 'main':
/Users/Mike/Library/Arduino15/packages/arduino/hardware/avr/1.6.19/cores/arduino/main.cpp:51:1: error: unable to find a register to spill in class 'NO_REGS'
}
^
/Users/Mike/Library/Arduino15/packages/arduino/hardware/avr/1.6.19/cores/arduino/main.cpp:51:1: error: this is the insn:
(insn 949 946 952 82 (set (mem:QI (post_dec:HI (reg/f:HI 32 SP_L)) [0 S1 A8])
(subreg:QI (reg/f:HI 465) 1)) /Users/Mike/Documents/Arduino/TouchBass2/TouchBass2.ino:867 1 {pushqi1}
(expr_list:REG_ARGS_SIZE (const_int 1 [0x1])
(nil)))
/Users/Mike/Library/Arduino15/packages/arduino/hardware/avr/1.6.19/cores/arduino/main.cpp:51: confused by earlier errors, bailing out
lto-wrapper: /Users/Mike/Library/Arduino15/packages/arduino/tools/avr-gcc/4.9.2-atmel3.5.4-arduino2/bin/avr-gcc returned 1 exit status
/Users/Mike/Library/Arduino15/packages/arduino/tools/avr-gcc/4.9.2-atmel3.5.4-arduino2/bin/../lib/gcc/avr/4.9.2/../../../../avr/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status
exit status 1
Error compiling for board Arduino/Genuino Uno.

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

Not exactly the same error message but this might be helpful: