Michael Hope wrote: > Hi Sergio. Any luck so far? Micheal, thanks for your inquiry. I made some progress, in fact.
I got the GO_IF_LEGITIMATE_ADDRESS() macro to detect correctly REG+IMM addresses, and then the LEGITIMIZE_ADDRESS() macro to force them to be pre-computed in a register. However, now the compiler freaks out with an ICE.. :-/ I put some details below. Thanks for any clue that you or others can give me. Cheers, Sergio ========================================================================== This is a fragment of my LEGITIMIZE_ADDRESS(): ----------------------------------------------------------------- rtx legitimize_address(rtx X,rtx OLDX, enum machine_mode MODE) { rtx op1,op2,op,sum; op=NULL; ... if(GET_CODE(X)==PLUS && !no_new_pseudos) { op1=XEXP(X,0); op2=XEXP(X,1); if(GET_CODE(op1) == CONST_INT && (GET_CODE(op2) == REG || GET_CODE(op2) == SUBREG)) // base displacement { sum = gen_rtx_PLUS (MODE, op1, op2); op = force_reg(MODE, sum); } ... ----------------------------------------------------------------- Now when compiling a simple program such as: void foobar(int par1, int par2, int parN) { int a,b; a = 0x1234; b = a; } the instructions (n. 8,12,13) which compute the addresses in registers seem to be generated correctly: ----------------------------------------------------------------- ;; Function foobar ;; Register dispositions: 37 in 4 38 in 2 39 in 4 40 in 2 41 in 2 ;; Hard regs used: 2 4 30 (note 2 0 3 NOTE_INSN_DELETED) (note 3 2 6 0 NOTE_INSN_FUNCTION_BEG) ;; Start of basic block 1, registers live: 1 [A1] 29 [B13] 30 [B14] (note 6 3 8 1 [bb 1] NOTE_INSN_BASIC_BLOCK) (insn 8 6 9 1 (set (reg/f:HI 4 A4 [37]) (plus:HI (reg/f:HI 30 B14) (const_int -16 [0xfffffffffffffff0]))) 9 {addhi3} (nil) (nil)) (insn 9 8 10 1 (set (reg:HI 2 A2 [38]) (const_int 4660 [0x1234])) 5 {*constant_load} (nil) (nil)) (insn 10 9 12 1 (set (mem/i:HI (reg/f:HI 4 A4 [37]) [0 a+0 S2 A32]) (reg:HI 2 A2 [38])) 7 {*store_word} (nil) (nil)) (insn 12 10 13 1 (set (reg/f:HI 4 A4 [39]) (plus:HI (reg/f:HI 30 B14) (const_int -14 [0xfffffffffffffff2]))) 9 {addhi3} (nil) (nil)) (insn 13 12 14 1 (set (reg/f:HI 2 A2 [40]) (plus:HI (reg/f:HI 30 B14) (const_int -16 [0xfffffffffffffff0]))) 9 {addhi3} (nil) (nil)) (insn 14 13 15 1 (set (reg:HI 2 A2 [orig:41 a ] [41]) (mem/i:HI (reg/f:HI 2 A2 [40]) [0 a+0 S2 A32])) 4 {*load_word} (nil) (nil)) (insn 15 14 16 1 (set (mem/i:HI (reg/f:HI 4 A4 [39]) [0 b+0 S2 A16]) (reg:HI 2 A2 [orig:41 a ] [41])) 7 {*store_word} (nil) (nil)) ;; End of basic block 1, registers live: 1 [A1] 29 [B13] 30 [B14] (note 16 15 25 NOTE_INSN_FUNCTION_END) (note 25 16 0 NOTE_INSN_DELETED) ----------------------------------------------------------------- However, when I compile it $ hcc -da foobar8.c I get an ICE at the end of the compilation, and the assembly source is not produced: [ lots of my debugging output removed ] legitimate_address2(non-strict, soft-reg allowed), X= (reg/f:HI 29 B13) legitimate_address2() yes: (X)==REG && non_strict_base_reg(REGNO(X)) -----------------MOVHI--------------- [generating a MOV X, Y insn] MOVHI: operands[0] (mem:HI (reg/f:HI 29 B13) [0 S2 A8]) MOVHI: operands[1] (reg:HI 31 B15) MOVHI --- END [then checking if -2(B13) is legitimate, it is not...] legitimate_address2(non-strict, soft-reg allowed), X= (plus:HI (reg/f:HI 29 B13) (const_int -2 [0xfffffffffffffffe])) legitimate_address2(): FOUND register+offset --> FAIL! legitimate_address2(non-strict, soft-reg allowed), X= (plus:HI (reg/f:HI 29 B13) (const_int -2 [0xfffffffffffffffe])) legitimate_address2(): FOUND register+offset --> FAIL! legitimate_address2(non-strict, soft-reg allowed), X= (plus:HI (reg/f:HI 29 B13) (const_int -2 [0xfffffffffffffffe])) legitimate_address2(): FOUND register+offset --> FAIL! legitimate_address2(non-strict, soft-reg allowed), X= (plus:HI (reg/f:HI 29 B13) (const_int -2 [0xfffffffffffffffe])) legitimate_address2(): FOUND register+offset --> FAIL! [and after four check of the add above, gcc 4.0.2 freaks out with ] foobar8.c: In function ‘foobar’: foobar8.c:7: internal compiler error: in change_address_1, at emit-rtl.c:1800 Please submit a full bug report, with preprocessed source if appropriate. See <URL:http://gcc.gnu.org/bugs.html> for instructions. The failed assertion is in line 1800: some "addr" is not an address. 1784 change_address_1 (rtx memref, enum machine_mode mode, rtx addr, int validate) 1785 { 1786 rtx new; 1787 1788 gcc_assert (MEM_P (memref)); 1789 if (mode == VOIDmode) 1790 mode = GET_MODE (memref); 1791 if (addr == 0) 1792 addr = XEXP (memref, 0); 1793 if (mode == GET_MODE (memref) && addr == XEXP (memref, 0) 1794 && (!validate || memory_address_p (mode, addr))) 1795 return memref; 1796 1797 if (validate) 1798 { 1799 if (reload_in_progress || reload_completed) 1800 gcc_assert (memory_address_p (mode, addr)); 1801 else 1802 addr = memory_address (mode, addr); 1803 } 1804 1805 if (rtx_equal_p (addr, XEXP (memref, 0)) && mode == GET_MODE (memref)) 1806 return memref; 1807 1808 new = gen_rtx_MEM (mode, addr); 1809 MEM_COPY_ATTRIBUTES (new, memref); 1810 return new; 1811 } Could it be the REG+OFF which the LEGITIMATE_ADDRESS() rejects above? But then why all the others before it get re-written by a call to LEGITIMIZE_ ADDRESS() ?! What is calling change_address_1() at the end of the compilation phase? Thanks Sergio ========================================================================== Sergio Ruocco wrote: > > Now my GO_IF_LEGITIMATE_ADDRESS refuses anything that is not a REG > or a CONSTANT_ADDRESS: > > int legitimate_address1(enum machine_mode MODE,rtx X) > { > if(CONSTANT_ADDRESS_P(X)) > return 1; > if(GET_CODE(X)==REG && is_base_reg(REGNO(X))) > return 1; > > return 0; /* fails everything else */ > > } /* this is the strict version, the non strict version is similar */ > > but GCC (4.0.2, just in case the version is relevant) still aborts the > compilation. > > > Then I found this wiki note about forcing complex addresses into > registers: http://gcc.gnu.org/wiki/WritingANewBackEnd > > ... > rtx copy_addr_to_reg (rtx x) > Equivalent to copy_to_mode_reg (Pmode, x). For example, this > function can be used to compute a complex address X in a register for an > instruction which supports only register indirect addressing. See also > replace_equiv_address() below. > ... > > > Thus I changed in the .md file the movXX RTL expand macro to force any > MEM expression into a register: > > (define_expand "movhi" /* my micro is 16 bit... */ > [(set (match_operand:HI 0 "nonimmediate_operand" "") > (match_operand:HI 1 "general_operand" "") > )] > "" > { > if(!no_new_pseudos && GET_CODE(operands[0])==MEM) { > if( /* addr in operands[0] == base reg + offset */ ) > operands[0] = copy_addr_to_reg ( operands[0] ); > } > ) > > The GCC still fails to generate the assembly code to do the arithmetic > computation of the baseReg+offset-->tempReg, and then use (tempReg) as > address. > > Note that with the current MD GCC is able to generate simple sums like > R1 = R2 + R3 and R1 = R2 + IMM, thus the basic math to compute an > address is there. > > Any suggestion on what I am doing wrong ? > > Sergio > > > Michael Hope wrote: >> Hi Sergio. My port has similar addressing modes - all memory must be >> accessed by one of two registers and can only be accessed indirectly, >> indirect with pre increment, and indirect with post increment. The >> key is GO_IF_LEGITIMATE_ADDRESS and the legitimate address helper >> function. Mine looks like this: >> >> /* Return 1 if the address is OK, otherwise 0. >> Used by GO_IF_LEGITIMATE_ADDRESS. */ >> >> bool >> tomi_legitimate_address (enum machine_mode mode ATTRIBUTE_UNUSED, >> rtx x, >> bool strict_checking) >> { >> /* (mem reg) */ >> if (REG_P (x) >> && tomi_reg_ok (x, strict_checking) >> ) >> { >> return 1; >> } >> >> if (GET_CODE(x) == PRE_DEC) >> { >> ... >> } >> >> if (GET_CODE(x) == POST_INC) >> { >> ... >> } >> >> return 0; >> } >> >> tomi_reg_ok returns true if x is any register when strict checking is >> clear and true if x is one of my addressing registers when strict >> checking is set. >> >> GCC will feed any memory accesses through this function to see if they >> are directly supported, and if not it will break them up into >> something smaller and try again. >> >> Hope that helps, >> >> -- Michael >> >> >> 2010/1/26 Sergio Ruocco <sergio.ruo...@gmail.com>: >>> Gabriel Paubert wrote: >>>> On Mon, Jan 25, 2010 at 01:34:09PM +0100, Sergio Ruocco wrote: >>>>> Hi everyone, >>>>> >>>>> I am porting GCC to a custom 16-bit microcontroller with very limited >>>>> addressing modes. Basically, it can only load/store using a (general >>>>> purpose) register as the address, without any offset: >>>>> >>>>> LOAD (R2) R1 ; load R1 from memory at address (R2) >>>>> STORE R1 (R2) ; store R1 to memory at address (R2) >>>>> >>>>> As far as I can understand, this is more limited than the current >>>>> architectures supported by GCC that I found in the current gcc/config/*. >>>> The Itanium (ia64) has the same limited choice of addressing modes. >>>> >>>> Gabriel >>> Thanks Gabriel. >>> >>> I dived into the ia64 md, but it is still unclear to me how the various >>> parts (macros, define_expand and define_insn in MD etc.) work together >>> to force the computation of a source/dest address plus offset into a >>> register... can anyone help me with this ? >>> >>> Thanks, >>> >>> Sergio >>> > >