diff options
Diffstat (limited to 'gcc/local-alloc.c')
| -rw-r--r-- | gcc/local-alloc.c | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/gcc/local-alloc.c b/gcc/local-alloc.c index a465bb7ffa3..9daf31dda14 100644 --- a/gcc/local-alloc.c +++ b/gcc/local-alloc.c @@ -67,6 +67,7 @@ Boston, MA 02111-1307, USA. */ #include "regs.h" #include "hard-reg-set.h" #include "insn-config.h" +#include "insn-attr.h" #include "recog.h" #include "output.h" @@ -1414,8 +1415,48 @@ block_alloc (b) q = qty_order[i]; if (qty_phys_reg[q] < 0) { +#ifdef INSN_SCHEDULING + /* These values represent the adjusted lifetime of a qty so + that it conflicts with qtys which appear near the start/end + of this qty's lifetime. + + The purpose behind extending the lifetime of this qty is to + discourage the register allocator from creating false + dependencies. + + The adjustment by the value +-3 indicates precisely that + this qty conflicts with qtys in the instructions immediately + before and after the lifetime of this qty. + + Experiments have shown that higher values tend to hurt + overall code performance. + + If allocation using the extended lifetime fails we will try + again with the qty's unadjusted lifetime. */ + int fake_birth = MAX (0, qty_birth[q] - 3); + int fake_death = MIN (insn_number * 2 + 1, qty_death[q] + 3); +#endif + if (N_REG_CLASSES > 1) { +#ifdef INSN_SCHEDULING + /* We try to avoid using hard registers allocated to qtys which + are born immediately after this qty or die immediately before + this qty. + + This optimization is only appropriate when we will run + a scheduling pass after reload and we are not optimizing + for code size. */ + if (flag_schedule_insns_after_reload && !optimize_size) + { + + qty_phys_reg[q] = find_free_reg (qty_min_class[q], + qty_mode[q], q, 0, 0, + fake_birth, fake_death); + if (qty_phys_reg[q] >= 0) + continue; + } +#endif qty_phys_reg[q] = find_free_reg (qty_min_class[q], qty_mode[q], q, 0, 0, qty_birth[q], qty_death[q]); @@ -1423,6 +1464,14 @@ block_alloc (b) continue; } +#ifdef INSN_SCHEDULING + /* Similarly, avoid false dependencies. */ + if (flag_schedule_insns_after_reload && !optimize_size + && qty_alternate_class[q] != NO_REGS) + qty_phys_reg[q] = find_free_reg (qty_alternate_class[q], + qty_mode[q], q, 0, 0, + fake_birth, fake_death); +#endif if (qty_alternate_class[q] != NO_REGS) qty_phys_reg[q] = find_free_reg (qty_alternate_class[q], qty_mode[q], q, 0, 0, |
