The following code for AVR target that reads from address space __memx result in wrong code: long readx (const __memx long *p) { return *p; } == compile == $ avr-gcc flash.c -S -dp -Os -mmcu=avr51 -da == configure == ../../gcc.gnu.org/trunk/configure --target=avr --prefix=/gnu/install/gcc-4.7 --disable-nls --with-dwarf2 --enable-checking=yes,rtl --enable-languages=c,c++ GNU C (GCC) version 4.8.0 20120304 (experimental) (avr) SVN 184887 from 2012-03-04 To see the bug RTL dumps will follow. There is really bloaty code from lower-subreg that splits the 4-byte move into 4 individual byte moves. After pass .peephole2 there are 4 xload_qi_libgcc insns that perform these moves. After pass .ce3 one of these moves is gone, this is wrong because no byte must be thrown away.
Created attachment 26824 [details] flash.c.208r.peephole2 This dump looks ok: there are 4 xload_qi_libgcc insns. peep2 did no optimizations except transform one (set (reg/f:PSI 12 r12 [58]) (const_int 2 [0x2])) to (parallel [(set (reg/f:PSI 12 r12 [58]) (const_int 2 [0x2])) (clobber (reg:QI 18 r18))]) which is ok (r18 is marked as dead above)
Created attachment 26825 [details] flash.c.209r.ce3 One xload_qi_libgcc has been killed.
Created attachment 26826 [details] flash.c
ce3 is correct in deleting the insn. The bug is that "xload<mode>_A" insn needs a clobber of r22 to represent the register footprint of the libcall generated in split1.
Author: gjl Date: Wed Mar 7 13:52:30 2012 New Revision: 185043 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=185043 Log: PR target/52484 * config/avr/avr.md (xload<mode>_A): Add R22... to register footprint. Modified: trunk/gcc/ChangeLog trunk/gcc/config/avr/avr.md
Author: gjl Date: Thu Mar 22 15:06:57 2012 New Revision: 185697 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=185697 Log: libgcc/ Backport from 2012-03-07 mainline r185033. PR target/52507 * config/avr/lib1funcs.S (__movmemx_hi): Fix loop label in RAM-part. Backport from 2012-03-07 mainline r185031. PR target/52505 * config/avr/lib1funcs.S (__xload_1): Don't read unintentionally from RAM. Backport from 2012-03-07 mainline r185030. PR target/52461 PR target/52508 * config/avr/lib1funcs.S (__do_copy_data): Clear RAMPZ after usage if RAMPZ affects reading from RAM. (__tablejump_elpm__): Ditto. (.xload): Ditto. (__movmemx_hi): Ditto. (__do_global_ctors): Right condition for RAMPZ usage is "have ELPM". (__do_global_dtors): Ditto. (__xload_1, __xload_2, __xload_3, __xload_4): Ditto. (__movmemx_hi): Ditto. gcc/ Backport from 2012-03-22 mainline r185692. PR target/52496 * config/avr/avr.md (unspec): Remove UNSPEC_MEMORY_BARRIER. (unspecv): Add UNSPECV_MEMORY_BARRIER. (cli_sei): Use unspec_volatile instead of unspec for memory barrier. (delay_cycles_1, delay_cycles_2): Ditto. (delay_cycles_3, delay_cycles_4): Ditto. (nopv, *nopv): Ditto. (sleep, *sleep): Ditto. (wdr, *wdr): Ditto. Backport from 2012-03-21 mainline r185605. PR rtl-optimization/52543 PR target/52461 * config/avr/avr-protos.h (avr_load_lpm): New prototype. * config/avr/avr.c (avr_mode_dependent_address_p): New function. (TARGET_MODE_DEPENDENT_ADDRESS_P): New define. (avr_load_libgcc_p): Restrict to __flash loads. (avr_out_lpm): Only handle 1-byte loads from __flash. (avr_load_lpm): New function. (avr_find_unused_d_reg): Remove. (avr_out_lpm_no_lpmx): Remove. (adjust_insn_length): Handle ADJUST_LEN_LOAD_LPM. * config/avr/avr.md (unspec): Add UNSPEC_LPM. (load_<mode>_libgcc): Use UNSPEC_LPM instead of MEM. (load_<mode>, load_<mode>_clobber): New insns. (mov<mode>): For multi-byte move from non-generic 16-bit address spaces: Expand to load_<mode> resp. load_<mode>_clobber. (load<mode>_libgcc): Remove expander. (split-lpmx): Remove split. Backport from 2012-03-13 mainline r185329. PR target/52488 * config/avr/avr.c (avr_prologue_setup_frame): Cut down stack offset (size) to a value the insns can deal with. (expand_epilogue): Ditto. Backport from 2012-03-12 mainline r185256. PR target/52499 * config/avr/avr.c (avr_mode_code_base_reg_class): Change return type from reg_class_t to enum reg_class. * config/avr/avr-protos.h (avr_mode_code_base_reg_class): Ditto. Backport from 2012-03-12 mainline r185253. PR target/52148 * config/avr/avr.c (avr_out_movmem): Fix typo in output template for the case ADDR_SPACE_FLASH and AVR_HAVE_LPMX introduced in r184615 from 2012-02-28. Backport from 2012-03-08 mainline r185105. * config/avr/avr.md (*addhi3, addhi3_clobber): Add "w" alternative for constants in [-63,63]. Backport from 2012-03-08 mainline r185100. PR target/52496 * config/avr/avr.c (avr_mem_clobber): New static function. (avr_expand_delay_cycles): Add memory clobber operand to delay_cycles_1, delay_cycles_2, delay_cycles_3, delay_cycles_4. * config/avr/avr.md (unspec): Add UNSPEC_MEMORY_BARRIER. (enable_interrupt, disable_interrupt): New expander. (nopv, sleep, wdr): New expanders. (delay_cycles_1): Add memory clobber. (delay_cycles_2): Add memory clobber. (delay_cycles_3): Add memory clobber. (delay_cycles_4): Add memory clobber. (cli_sei): New insn from former "enable_interrupt", "disable_interrupt" with memory clobber. (*wdt): New insn from former "wdt" with memory clobber. (*nopv): Similar, but for "nopv". (*sleep): Similar, but for "sleep". Backport from 2012-03-07 mainline r185043. PR target/52484 * config/avr/avr.md (xload<mode>_A): Add R22... to register footprint. Backport from 2012-03-07 mainline r185032. PR target/52506 * gcc/config/avr/avr.c (expand_epilogue): Fix order of restoration to: RAMPZ, RAMPY, RAMPX, RAMPD. (expand_prologue): Only clear RAMPZ if it has effect on RAM-read. Backport from 2012-03-07 mainline r185031. PR target/52505 * config/avr/avr.c (avr_out_xload): Don't read unintentionally from RAM. * config/avr/avr.md (xload_8): Adjust insn length. Backport from 2012-03-07 mainline r185030. PR target/52461 * gcc/config/avr/avr.c (avr_out_lpm): Clear RAMPZ after usage if RAMPZ affects reading from RAM. Backport from 2012-03-05 mainline r184919. * config/avr/avr.md (*umaddqihi4.2): New insn-and-split. Modified: branches/gcc-4_7-branch/gcc/ChangeLog branches/gcc-4_7-branch/gcc/config/avr/avr-protos.h branches/gcc-4_7-branch/gcc/config/avr/avr.c branches/gcc-4_7-branch/gcc/config/avr/avr.md branches/gcc-4_7-branch/libgcc/ChangeLog branches/gcc-4_7-branch/libgcc/config/avr/lib1funcs.S
Fixed in 4.7.1