diff options
| -rw-r--r-- | gcc/ChangeLog | 6 | ||||
| -rw-r--r-- | gcc/reg-stack.c | 61 |
2 files changed, 52 insertions, 15 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index c828107acf0..c2e586500a2 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2004-12-11 Roger Sayle <roger@eyesopen.com> + + * reg-stack.c (change_stack): Avoid placing the new top-of-stack in + its correct location during popping if we need to permute the stack + afterwards. Attempt to preserve the original stack ordering. + 2004-12-12 Kazu Hirata <kazu@cs.umass.edu> * lcm.c (optimize_mode_switching): Free insert and delete in diff --git a/gcc/reg-stack.c b/gcc/reg-stack.c index 11dd8495e88..2ba963efcc5 100644 --- a/gcc/reg-stack.c +++ b/gcc/reg-stack.c @@ -2374,13 +2374,14 @@ change_stack (rtx insn, stack old, stack new, enum emit_where where) { bool slots[REG_STACK_SIZE]; int pops[REG_STACK_SIZE]; - int next, dest; + int next, dest, topsrc; /* First pass to determine the free slots. */ for (reg = 0; reg <= new->top; reg++) slots[reg] = TEST_HARD_REG_BIT (new->reg_set, old->reg[reg]); /* Second pass to allocate preferred slots. */ + topsrc = -1; for (reg = old->top; reg > new->top; reg--) if (TEST_HARD_REG_BIT (new->reg_set, old->reg[reg])) { @@ -2388,6 +2389,10 @@ change_stack (rtx insn, stack old, stack new, enum emit_where where) for (next = 0; next <= new->top; next++) if (!slots[next] && new->reg[next] == old->reg[reg]) { + /* If this is a preference for the new top of stack, record + the fact by remembering it's old->reg in topsrc. */ + if (next == new->top) + topsrc = reg; slots[next] = true; dest = next; break; @@ -2397,8 +2402,23 @@ change_stack (rtx insn, stack old, stack new, enum emit_where where) else pops[reg] = reg; + /* Intentionally, avoid placing the top of stack in it's correct + location, if we still need to permute the stack below and we + can usefully place it somewhere else. This is the case if any + slot is still unallocated, in which case we should place the + top of stack there. */ + if (topsrc != -1) + for (reg = 0; reg < new->top; reg++) + if (!slots[reg]) + { + pops[topsrc] = reg; + slots[new->top] = false; + slots[reg] = true; + break; + } + /* Third pass allocates remaining slots and emits pop insns. */ - next = 0; + next = new->top; for (reg = old->top; reg > new->top; reg--) { dest = pops[reg]; @@ -2406,27 +2426,38 @@ change_stack (rtx insn, stack old, stack new, enum emit_where where) { /* Find next free slot. */ while (slots[next]) - next++; - dest = next++; + next--; + dest = next--; } emit_pop_insn (insn, old, FP_MODE_REG (old->reg[dest], DFmode), EMIT_BEFORE); } } else - /* The following loop attempts to maximize the number of times we - pop the top of the stack, as this permits the use of the faster - ffreep instruction on platforms that support it. */ - for (reg = 0; reg <= old->top; reg++) - if (! TEST_HARD_REG_BIT (new->reg_set, old->reg[reg])) - { - while (old->top > reg - && ! TEST_HARD_REG_BIT (new->reg_set, old->reg[old->top])) - emit_pop_insn (insn, old, FP_MODE_REG (old->reg[old->top], DFmode), + { + /* The following loop attempts to maximize the number of times we + pop the top of the stack, as this permits the use of the faster + ffreep instruction on platforms that support it. */ + int live, next; + + live = 0; + for (reg = 0; reg <= old->top; reg++) + if (TEST_HARD_REG_BIT (new->reg_set, old->reg[reg])) + live++; + + next = live; + while (old->top >= live) + if (TEST_HARD_REG_BIT (new->reg_set, old->reg[old->top])) + { + while (TEST_HARD_REG_BIT (new->reg_set, old->reg[next])) + next--; + emit_pop_insn (insn, old, FP_MODE_REG (old->reg[next], DFmode), EMIT_BEFORE); - emit_pop_insn (insn, old, FP_MODE_REG (old->reg[reg], DFmode), + } + else + emit_pop_insn (insn, old, FP_MODE_REG (old->reg[old->top], DFmode), EMIT_BEFORE); - } + } if (new->top == -2) { |