diff options
Diffstat (limited to 'gcc/flow.c')
| -rw-r--r-- | gcc/flow.c | 32 |
1 files changed, 29 insertions, 3 deletions
@@ -2859,7 +2859,7 @@ life_analysis (f, file, flags) { rtx insn; - /* Search for any REG_LABEL notes whih reference deleted labels. */ + /* Search for any REG_LABEL notes which reference deleted labels. */ for (insn = get_insns (); insn; insn = NEXT_INSN (insn)) { rtx inote = find_reg_note (insn, REG_LABEL, NULL_RTX); @@ -3385,6 +3385,24 @@ calculate_global_regs_live (blocks_in, blocks_out, flags) if (blocks_out) sbitmap_zero (blocks_out); + /* We work through the queue until there are no more blocks. What + is live at the end of this block is precisely the union of what + is live at the beginning of all its successors. So, we set its + GLOBAL_LIVE_AT_END field based on the GLOBAL_LIVE_AT_START field + for its successors. Then, we compute GLOBAL_LIVE_AT_START for + this block by walking through the instructions in this block in + reverse order and updating as we go. If that changed + GLOBAL_LIVE_AT_START, we add the predecessors of the block to the + queue; they will now need to recalculate GLOBAL_LIVE_AT_END. + + We are guaranteed to terminate, because GLOBAL_LIVE_AT_START + never shrinks. If a register appears in GLOBAL_LIVE_AT_START, it + must either be live at the end of the block, or used within the + block. In the latter case, it will certainly never disappear + from GLOBAL_LIVE_AT_START. In the former case, the register + could go away only if it disappeared from GLOBAL_LIVE_AT_START + for one of the successor blocks. By induction, that cannot + occur. */ while (qhead != qtail) { int rescan, changed; @@ -3396,7 +3414,7 @@ calculate_global_regs_live (blocks_in, blocks_out, flags) qhead = queue; bb->aux = NULL; - /* Begin by propogating live_at_start from the successor blocks. */ + /* Begin by propagating live_at_start from the successor blocks. */ CLEAR_REG_SET (new_live_at_end); for (e = bb->succ; e; e = e->succ_next) { @@ -4609,7 +4627,11 @@ mark_set_regs (pbi, x, insn) } } -/* Process a single SET rtx, X. */ +/* Process a single set, which appears in INSN. REG (which may not + actually be a REG, it may also be a SUBREG, PARALLEL, etc.) is + being set using the CODE (which may be SET, CLOBBER, or COND_EXEC). + If the set is conditional (because it appear in a COND_EXEC), COND + will be the condition. */ static void mark_set_1 (pbi, code, reg, cond, insn, flags) @@ -6258,6 +6280,10 @@ dump_regset (r, outf) }); } +/* Print a human-reaable representation of R on the standard error + stream. This function is designed to be used from within the + debugger. */ + void debug_regset (r) regset r; |