On Sun, Jan 19, 2014 at 6:24 AM, Uros Bizjak <ubiz...@gmail.com> wrote: > On Sun, Jan 19, 2014 at 3:20 PM, H.J. Lu <hjl.to...@gmail.com> wrote: > >>>> For LEA operation with SImode_address_operand, which zero-extends SImode >>>> to DImode, ix86_split_lea_for_addr turns >>>> >>>> (set (reg:DI) ...) >>>> >>>> into >>>> >>>> (set (reg:SI) ...) >>>> >>>> We need to do >>>> >>>> (set (reg:DI) (zero_extend:DI (reg:SI))) >>>> >>>> at the end. If the LEA operation is >>>> >>>> (set (reg:DI) (zero_extend:DI (reg:SI))) >>> >>> ree pass should remove these. However, we can just emit zero-extend >>> insn at the end of sequence, and ree (which is located after >>> post-reload split) should handle it: >>> >>> --cut here-- >>> Index: config/i386/i386.md >>> =================================================================== >>> --- config/i386/i386.md (revision 206753) >>> +++ config/i386/i386.md (working copy) >>> @@ -5428,12 +5428,17 @@ >>> operands[0] = SET_DEST (pat); >>> operands[1] = SET_SRC (pat); >>> >>> - /* Emit all operations in SImode for zero-extended addresses. Recall >>> - that x86_64 inheretly zero-extends SImode operations to DImode. */ >>> + /* Emit all operations in SImode for zero-extended addresses. */ >>> if (SImode_address_operand (operands[1], VOIDmode)) >>> mode = SImode; >>> >>> ix86_split_lea_for_addr (curr_insn, operands, mode); >>> + >>> + /* Zero-extend return register to DImode for zero-extended addresses. */ >>> + if (mode != <MODE>mode) >>> + emit_insn (gen_zero_extendsidi2 >>> + (operands[0], gen_lowpart ((mode), operands[0]))); >>> + >>> DONE; >>> } >>> [(set_attr "type" "lea") >>> --cut here-- >>> >>> The patch was tested with a testcase from Comment #9 of the PR using >>> "-O --march=corei7 -mtune=slm", and resulting binary runs without >>> problems. >>> >> >> Yes, the resulting GCC works correctly. However, we generate >> extra >> >> (set (reg:DI) (zero_extend:DI (reg:SI))) >> >> It is because we generate >> >> (set (reg:SI) (reg:SI) >> (set (reg:DI) (zero_extend:DI (reg:SI))) >> >> REE pass doesn't know >> >> (set (reg:SI) (reg:SI) >> >> has an implicit ZERO_EXTEND. Here is a testcase: > > This is the correct sequence,and REE pass should be improved to handle > this situation. > > Note, that the problem was that we assumed SImode operations > (including move) have implicit DImode zero-extend, but in fact we > haven't communicate this to the compiler in a proper way. > > So, I propose we go with my patch and file an enhancement PR for the REE pass. >
That is fine with me. Please install it on all affected branches and close the PR. I will open a new PR for REE pass. Thanks. -- H.J.
