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[PATCH][RFA] Teach more transformations in ifcvt.c how to update the CFG
On Sunday 07 January 2007 23:03, Steven Bosscher wrote:
> Hi,
>
> This is an "upgrade" of yesterday's patch.
And this is the final version.
> This was bootstrapped and tested on {ia64,x86_64}-unknown-linux-gnu.
This updated patch was bootstrapped on x86_64-unknown-linux-gnu.
The only change is that I removed b_unconditional, but I had an
assert for that in the compilers I bootstrapped previously (which
wasn't in the patch I posted).
> I don't ask for approval yet because I want to look into the generated
> code a bit first.
I've done this now.
There are some minor code changes due to changes in which we process
the blocks, but this doesn't lead to any other changes than some
different regalloc/scheduler choices and changed label numbers. I.e.
nothing I'm very worried about.
So I'd like to request approval for this patch, please.
I have a few more changes in the queue that make it easier to gather
statistics about the transformations that ifcvt is doing. But I'll
first try to enable cfglayout mode when this patch goes in, and see
if this buys us the compiler speedups I'm looking for...
Thanks,
Gr.
Steven
* ifcvt.c (struct noce_if_info): Add comments to the fields.
Remove the b_unconditional field.
(noce_try_sign_mask): Do not look at b_unconditional.
(noce_process_if_block): Do not use merge_if_blocks. Update
the CFG here. Do not set b_unconditional.
(cond_move_process_if_block): Likewise.
(find_cond_trap): Likewise.
(check_cond_move_block): Require simple jump insns at the end
of the basic block.
Index: ifcvt.c
===================================================================
--- ifcvt.c (revision 120620)
+++ ifcvt.c (working copy)
@@ -596,12 +596,31 @@ cond_exec_process_if_block (ce_if_block_
struct noce_if_info
{
+ /* A basic block that ends in a simple conditional jump. */
basic_block test_bb;
+
+ /* The jump that ends TEST_BB. */
+ rtx jump;
+
+ /* The jump condition. */
+ rtx cond;
+
+ /* New insns should be inserted before this one. */
+ rtx cond_earliest;
+
+ /* Insns in the THEN and ELSE block. There is always just this
+ one insns in those blocks. The insns are single_set insns.
+ If there was no ELSE block, INSN_B is the last insn before
+ COND_EARLIEST, or NULL_RTX. In the former case, the insn
+ operands are still valid, as if INSN_B was moved down below
+ the jump. */
rtx insn_a, insn_b;
- rtx x, a, b;
- rtx jump, cond, cond_earliest;
- /* True if "b" was originally evaluated unconditionally. */
- bool b_unconditional;
+
+ /* The SET_SRC of INSN_A and INSN_B. */
+ rtx a, b;
+
+ /* The SET_DEST of INSN_A. */
+ rtx x;
};
static rtx noce_emit_store_flag (struct noce_if_info *, rtx, int, int);
@@ -1877,9 +1896,10 @@ noce_try_sign_mask (struct noce_if_info
return FALSE;
/* This is only profitable if T is cheap, or T is unconditionally
- executed/evaluated in the original insn sequence. */
+ executed/evaluated in the original insn sequence. The latter
+ happens if INSN_B was taken from TEST_BB. */
if (rtx_cost (t, SET) >= COSTS_N_INSNS (2)
- && (!if_info->b_unconditional
+ && (BLOCK_FOR_INSN (if_info->insn_b) != if_info->test_bb
|| t != if_info->b))
return FALSE;
@@ -2173,6 +2193,7 @@ noce_process_if_block (struct ce_if_bloc
basic_block test_bb = ce_info->test_bb; /* test block */
basic_block then_bb = ce_info->then_bb; /* THEN */
basic_block else_bb = ce_info->else_bb; /* ELSE or NULL */
+ basic_block join_bb;
struct noce_if_info if_info;
rtx insn_a, insn_b;
rtx set_a, set_b;
@@ -2283,7 +2304,6 @@ noce_process_if_block (struct ce_if_bloc
if_info.x = x;
if_info.a = a;
if_info.b = b;
- if_info.b_unconditional = else_bb == 0;
/* Try optimizations in some approximation of a useful order. */
/* ??? Should first look to see if X is live incoming at all. If it
@@ -2364,39 +2384,47 @@ noce_process_if_block (struct ce_if_bloc
return FALSE;
success:
- /* The original sets may now be killed. */
- delete_insn (insn_a);
-
- /* Several special cases here: First, we may have reused insn_b above,
- in which case insn_b is now NULL. Second, we want to delete insn_b
- if it came from the ELSE block, because follows the now correct
- write that appears in the TEST block. However, if we got insn_b from
- the TEST block, it may in fact be loading data needed for the comparison.
- We'll let life_analysis remove the insn if it's really dead. */
- if (insn_b && else_bb)
- delete_insn (insn_b);
-
- /* The new insns will have been inserted immediately before the jump. We
- should be able to remove the jump with impunity, but the condition itself
- may have been modified by gcse to be shared across basic blocks. */
- delete_insn (jump);
/* If we used a temporary, fix it up now. */
if (orig_x != x)
{
+ rtx seq;
+
start_sequence ();
noce_emit_move_insn (orig_x, x);
- insn_b = get_insns ();
+ seq = get_insns ();
set_used_flags (orig_x);
- unshare_all_rtl_in_chain (insn_b);
+ unshare_all_rtl_in_chain (seq);
end_sequence ();
- emit_insn_after_setloc (insn_b, BB_END (test_bb), INSN_LOCATOR (insn_a));
+ emit_insn_before_setloc (seq, BB_END (test_bb), INSN_LOCATOR (insn_a));
+ }
+
+ /* The original THEN and ELSE blocks may now be removed. The test block
+ must now jump to the join block. If the test block and the join block
+ can be merged, do so. */
+
+ join_bb = single_succ (then_bb);
+ if (else_bb)
+ {
+ delete_basic_block (else_bb);
+ num_true_changes++;
}
+ else
+ remove_edge (find_edge (test_bb, join_bb));
- /* Merge the blocks! */
- merge_if_block (ce_info);
+ remove_edge (find_edge (then_bb, join_bb));
+ redirect_edge_and_branch_force (single_succ_edge (test_bb), join_bb);
+ delete_basic_block (then_bb);
+ num_true_changes++;
+
+ if (can_merge_blocks_p (test_bb, join_bb))
+ {
+ merge_blocks (test_bb, join_bb);
+ num_true_changes++;
+ }
+ num_updated_if_blocks++;
return TRUE;
}
@@ -2463,6 +2491,12 @@ check_cond_move_block (basic_block bb, r
return FALSE;
}
+ /* We can only handle simple jumps at the end of the basic block.
+ It is almost impossible to update the CFG otherwise. */
+ insn = BB_END (bb);
+ if (JUMP_P (insn) && ! onlyjump_p (insn))
+ return FALSE;
+
return TRUE;
}
@@ -2537,10 +2571,12 @@ cond_move_convert_if_block (struct noce_
static int
cond_move_process_if_block (struct ce_if_block *ce_info)
{
+ basic_block test_bb = ce_info->test_bb;
basic_block then_bb = ce_info->then_bb;
basic_block else_bb = ce_info->else_bb;
+ basic_block join_bb;
struct noce_if_info if_info;
- rtx jump, cond, insn, seq, loc_insn;
+ rtx jump, cond, seq, loc_insn;
int max_reg, size, c, i;
rtx *then_vals;
rtx *else_vals;
@@ -2624,21 +2660,30 @@ cond_move_process_if_block (struct ce_if
}
emit_insn_before_setloc (seq, jump, INSN_LOCATOR (loc_insn));
- FOR_BB_INSNS (then_bb, insn)
- if (INSN_P (insn) && !JUMP_P (insn))
- delete_insn (insn);
+ join_bb = single_succ (then_bb);
if (else_bb)
{
- FOR_BB_INSNS (else_bb, insn)
- if (INSN_P (insn) && !JUMP_P (insn))
- delete_insn (insn);
+ delete_basic_block (else_bb);
+ num_true_changes++;
}
- delete_insn (jump);
+ else
+ remove_edge (find_edge (test_bb, join_bb));
- merge_if_block (ce_info);
+ remove_edge (find_edge (then_bb, join_bb));
+ redirect_edge_and_branch_force (single_succ_edge (test_bb), join_bb);
+ delete_basic_block (then_bb);
+ num_true_changes++;
+
+ if (can_merge_blocks_p (test_bb, join_bb))
+ {
+ merge_blocks (test_bb, join_bb);
+ num_true_changes++;
+ }
+ num_updated_if_blocks++;
return TRUE;
}
+
/* Attempt to convert an IF-THEN or IF-THEN-ELSE block into
straight line code. Return true if successful. */
@@ -3201,29 +3246,20 @@ find_cond_trap (basic_block test_bb, edg
if (seq == NULL)
return FALSE;
- num_true_changes++;
-
/* Emit the new insns before cond_earliest. */
emit_insn_before_setloc (seq, cond_earliest, INSN_LOCATOR (trap));
/* Delete the trap block if possible. */
remove_edge (trap_bb == then_bb ? then_edge : else_edge);
if (EDGE_COUNT (trap_bb->preds) == 0)
- delete_basic_block (trap_bb);
-
- /* If the non-trap block and the test are now adjacent, merge them.
- Otherwise we must insert a direct branch. */
- if (test_bb->next_bb == other_bb)
{
- struct ce_if_block new_ce_info;
- delete_insn (jump);
- memset (&new_ce_info, '\0', sizeof (new_ce_info));
- new_ce_info.test_bb = test_bb;
- new_ce_info.then_bb = NULL;
- new_ce_info.else_bb = NULL;
- new_ce_info.join_bb = other_bb;
- merge_if_block (&new_ce_info);
+ delete_basic_block (trap_bb);
+ num_true_changes++;
}
+
+ /* Wire together the blocks again. */
+ if (current_ir_type () == IR_RTL_CFGLAYOUT)
+ single_succ_edge (test_bb)->flags |= EDGE_FALLTHRU;
else
{
rtx lab, newjump;
@@ -3233,10 +3269,16 @@ find_cond_trap (basic_block test_bb, edg
LABEL_NUSES (lab) += 1;
JUMP_LABEL (newjump) = lab;
emit_barrier_after (newjump);
+ }
+ delete_insn (jump);
- delete_insn (jump);
+ if (can_merge_blocks_p (test_bb, other_bb))
+ {
+ merge_blocks (test_bb, other_bb);
+ num_true_changes++;
}
+ num_updated_if_blocks++;
return TRUE;
}