Hi !!
- Long time ago I've used Keil's IDE (µVision=C51) , evaluation version (2KB limited) with AT89C2051 chips (2KB Flash) First class C compiler for a chip not very C friendly.....
Still available ? Maybe :https://www.instructables.com/8051-Programming-Using-Keil-UVision-IDE/
-
IAR Embedded workbench for 8051 is 4KB limited .... and 14 days limited

-
Here is the Winckenhaûser µC/51 , 8kb limited demo (never used)
-
SDCC as full and free fallback path....