This should not be posted to the gcc list. You want gcc-help. Mohamed Shafi writes: > Hello all, > > Can anyone tell me what the below expression means ? It's a memory clobber. It doesn't actually do anything itself, but it prevents expressions that touch memory from being moved over it. > (insn 38 37 40 4 (parallel [ > (asm_operands/v ("") ("") 0 [ //line 2 > (reg:SI 32 [ s5.1 ]) > //line 3 > ] > [ > (asm_input:SI ("r")) > //line 6 > ] ("test55.c") 42) > //line 7 > (clobber (mem:BLK (scratch) [0 A8])) > //line 8 > ]) -1 (nil) > (nil)) > > in line 2, what is the 0 for? > > what does line 3 mean?what is it purpose ? > > In line 7 test55.c is the file name . why is it needed and what is 42? > In line 8 what does [0 A8] mean? Why is the filename needed? For debugging. As for the rest: I can't remember. Read the source. Andrew.