"Fran Baena" <[EMAIL PROTECTED]> writes: >> By the way, RTL is not really machine-independent. The data >> structures are machine independent. But the contents are not. You >> can not, even in principle, take the RTL generated for one processor >> and compile it on another processor. > > I thought that RTL represented something close to the target machine, > but not machine-dependent. I firstly thought that the output of the > middle-end was an RTL machine-independent representation, to which is > applied a few low-optimization machine-independent passes, and after > that is translated to a RTL machine-dependent to be applied other > optimization passes.
RTL is created using named patterns in the MD file, so even the creation process is machine-dependent. This is most obvious in the use of unspec, but it is true in general. > I read the rtl.def and rtl.h files, are very interesting, and i better > understand the whole process. But reading the output files by debuggin > options (-fdump-rtl-all) i have seen instructions like this: > > (insn 8 6 10 1 (set (mem/c/i:SI (plus:DI (reg/f:DI 54 virtual-stack-vars) > (const_int -8 [0xfffffffffffffff8])) [0 a+0 S4 A64]) > (const_int 1 [0x1])) -1 (nil) > (nil)) > > Among the multiple questions that appears i have a particular one, > what does "8 6 10 1" represents? Is it the "print format" defined in > rtl.def? 8 is in the INSN uid. 6 is the previous INSN uid. 10 is the next insn UID. 1 is the number of the basic block holding the insn. In general RTL is printed according to the format in rtl.def. There are a couple of exceptions; one of those exceptions is that field 4 of an insn, INSN_LOCATOR, is only printed if it is present. See line 391 of print-rtl.c. Ian
