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(find_basic_blocks): Ensure each live basic block is actually reachable. 

(life_analysis): Clean up handling of basic_block_drops_in.

From-SVN: r8340
This commit is contained in:
Richard Kenner 1994-10-26 07:33:33 -04:00
parent fd12bc82da
commit af14ce9ca9
1 changed files with 17 additions and 3 deletions
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20
gcc/flow.c
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@ -608,6 +608,20 @@ find_basic_blocks (f, nonlocal_label_list)
}
}
/* ??? See if we have a "live" basic block that is not reachable.
This can happen if it is headed by a label that is preserved or
in one of the label lists, but no call or computed jump is in
the loop. It's not clear if we can delete the block or not,
but don't for now. However, we will mess up register status if
it remains unreachable, so add a fake reachability from the
previous block. */
for (i = 1; i < n_basic_blocks; i++)
if (block_live[i] && ! basic_block_drops_in[i]
&& GET_CODE (basic_block_head[i]) == CODE_LABEL
&& LABEL_REFS (basic_block_head[i]) == basic_block_head[i])
basic_block_drops_in[i] = 1;
/* Now delete the code for any basic blocks that can't be reached.
They can occur because jump_optimize does not recognize
unreachable loops as unreachable. */
@ -1061,18 +1075,18 @@ life_analysis (f, nregs)
{
register rtx jump, head;
/* Update the basic_block_new_live_at_end's of the block
that falls through into this one (if any). */
head = basic_block_head[i];
jump = PREV_INSN (head);
if (basic_block_drops_in[i])
{
register int from_block = BLOCK_NUM (jump);
register int j;
for (j = 0; j < regset_size; j++)
basic_block_new_live_at_end[from_block][j]
basic_block_new_live_at_end[i-1][j]
|= basic_block_live_at_start[i][j];
}
/* Update the basic_block_new_live_at_end's of
all the blocks that jump to this one. */
if (GET_CODE (head) == CODE_LABEL)