diff options
Diffstat (limited to 'gnu/egcs/gcc/cse.c')
| -rw-r--r-- | gnu/egcs/gcc/cse.c | 61 |
1 files changed, 14 insertions, 47 deletions
diff --git a/gnu/egcs/gcc/cse.c b/gnu/egcs/gcc/cse.c index 35dfaa79028..8b87c72fb1e 100644 --- a/gnu/egcs/gcc/cse.c +++ b/gnu/egcs/gcc/cse.c @@ -1,5 +1,5 @@ /* Common subexpression elimination for GNU compiler. - Copyright (C) 1987, 88, 89, 92-7, 1998, 1999 Free Software Foundation, Inc. + Copyright (C) 1987, 88, 89, 92-99, 2000 Free Software Foundation, Inc. This file is part of GNU CC. @@ -42,12 +42,14 @@ Boston, MA 02111-1307, USA. */ expressions encountered with the cheapest equivalent expression. It is too complicated to keep track of the different possibilities - when control paths merge; so, at each label, we forget all that is - known and start fresh. This can be described as processing each - basic block separately. Note, however, that these are not quite - the same as the basic blocks found by a later pass and used for - data flow analysis and register packing. We do not need to start fresh - after a conditional jump instruction if there is no label there. + when control paths merge in this code; so, at each label, we forget all + that is known and start fresh. This can be described as processing each + extended basic block separately. We have a separate pass to perform + global CSE. + + Note CSE can turn a conditional or computed jump into a nop or + an unconditional jump. When this occurs we arrange to run the jump + optimizer after CSE to delete the unreachable code. We use two data structures to record the equivalent expressions: a hash table for most expressions, and several vectors together @@ -7496,7 +7498,6 @@ cse_insn (insn, libcall_insn) rtx new = emit_jump_insn_before (gen_jump (XEXP (src, 0)), insn); JUMP_LABEL (new) = XEXP (src, 0); LABEL_NUSES (XEXP (src, 0))++; - delete_insn (insn); insn = new; } else @@ -7507,42 +7508,11 @@ cse_insn (insn, libcall_insn) Until the right place is found, might as well do this here. */ INSN_CODE (insn) = -1; - /* Now that we've converted this jump to an unconditional jump, - there is dead code after it. Delete the dead code until we - reach a BARRIER, the end of the function, or a label. Do - not delete NOTEs except for NOTE_INSN_DELETED since later - phases assume these notes are retained. */ - - p = insn; - - while (NEXT_INSN (p) != 0 - && GET_CODE (NEXT_INSN (p)) != BARRIER - && GET_CODE (NEXT_INSN (p)) != CODE_LABEL) - { - /* Note, we must update P with the return value from - delete_insn, otherwise we could get an infinite loop - if NEXT_INSN (p) had INSN_DELETED_P set. */ - if (GET_CODE (NEXT_INSN (p)) != NOTE - || NOTE_LINE_NUMBER (NEXT_INSN (p)) == NOTE_INSN_DELETED) - p = PREV_INSN (delete_insn (NEXT_INSN (p))); - else - p = NEXT_INSN (p); - } - - /* If we don't have a BARRIER immediately after INSN, put one there. - Much code assumes that there are no NOTEs between a JUMP_INSN and - BARRIER. */ - - if (NEXT_INSN (insn) == 0 - || GET_CODE (NEXT_INSN (insn)) != BARRIER) - emit_barrier_before (NEXT_INSN (insn)); - - /* We might have two BARRIERs separated by notes. Delete the second - one if so. */ - - if (p != insn && NEXT_INSN (p) != 0 - && GET_CODE (NEXT_INSN (p)) == BARRIER) - delete_insn (NEXT_INSN (p)); + /* Now emit a BARRIER after the unconditional jump. Do not bother + deleting any unreachable code, let jump/flow do that. */ + if (NEXT_INSN (insn) != 0 + && GET_CODE (NEXT_INSN (insn)) != BARRIER) + emit_barrier_after (insn); cse_jumps_altered = 1; sets[i].rtl = 0; @@ -9035,9 +9005,6 @@ cse_basic_block (from, to, next_branch, around_loop) insn = NEXT_INSN (to); - if (LABEL_NUSES (to) == 0) - insn = delete_insn (to); - /* If TO was the last insn in the function, we are done. */ if (insn == 0) return 0; |