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authorMagnus Lång <[email protected]>2016-09-01 20:10:12 +0200
committerMagnus Lång <[email protected]>2016-09-05 15:02:03 +0200
commit69e338f4a85f47ad2d8c1b63adb761006dc4a979 (patch)
tree2dcb2152fa3257e3fe37b9090ecfdd85d02f86fb
parent904caa71a3754e3ee7f681cc7d4106d4a9979f1f (diff)
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hipe_regalloc_prepass: Change splitting heuristic
The division into an initial pass that may introduce temps, and following passes that must not forces us to make the same heuristic decision during each of these passes. Thus, the splitting heuristic can't be based on the number of temporaries -- at least without excluding temporaries above SpillLimit.
-rw-r--r--lib/hipe/regalloc/hipe_regalloc_prepass.erl21
1 files changed, 13 insertions, 8 deletions
diff --git a/lib/hipe/regalloc/hipe_regalloc_prepass.erl b/lib/hipe/regalloc/hipe_regalloc_prepass.erl
index 5a52e5ad51..c2531bc451 100644
--- a/lib/hipe/regalloc/hipe_regalloc_prepass.erl
+++ b/lib/hipe/regalloc/hipe_regalloc_prepass.erl
@@ -60,8 +60,8 @@
-define(TUNE_TOO_FEW_BBS, 256).
%% Ignore the ra_partitioned option (and do whole function RA instead) when
-%% there are fewer than ?TUNE_MIN_SPLIT_PSEUDOS non-spilled used pseudos.
--define(TUNE_MIN_SPLIT_PSEUDOS, 1024).
+%% there are fewer than ?TUNE_MIN_SPLIT_BBS basic blocks.
+-define(TUNE_MIN_SPLIT_BBS, 384).
%% We present a "pseudo-target" to the register allocator we wrap.
%% Note: all arities are +1 as we're currently using the parameterised module
@@ -145,7 +145,12 @@ regalloc(RegAllocMod, CFG, SpillIndex0, SpillLimit, Target, Options) ->
Liveness),
{Coloring, SpillIndex, Liveness}.
-%% regalloc_initial/6 is allowed to introduce new temporaries, unlike regalloc/6
+%% regalloc_initial/6 is allowed to introduce new temporaries, unlike
+%% regalloc/6.
+%% In order for regalloc/6 to never introduce temporaries, regalloc/6 must never
+%% choose to do split allocation unless regalloc_initial/6 does. This is the
+%% reason that the splitting heuristic is solely based on the number of basic
+%% blocks, which does not change during the register allocation loop.
-spec regalloc_initial(module(), target_cfg(), spillno(), spillno(), module(),
proplists:proplist())
-> {hipe_map(), spillno(), target_cfg(),
@@ -169,12 +174,11 @@ regalloc_1(RegAllocMod, CFG0, SpillIndex0, SpillLimit, Target, Options,
{ScanBBs, Seen, SpillMap, SpillIndex1} =
scan_cfg(CFG0, Liveness, SpillIndex0, Target),
- AllPrecoloured = Target:all_precoloured(),
-
{PartColoring, SpillIndex, NewCFG} =
- case proplists:get_bool(ra_partitioned, Options) of
- true when map_size(Seen) - map_size(SpillMap) - length(AllPrecoloured)
- > ?TUNE_MIN_SPLIT_PSEUDOS ->
+ case proplists:get_bool(ra_partitioned, Options)
+ andalso length(Target:labels(CFG0)) > ?TUNE_MIN_SPLIT_BBS
+ of
+ true ->
regalloc_partitioned(SpillMap, SpillIndex1, SpillLimit, ScanBBs,
CFG0, Target, RegAllocMod, Options);
_ ->
@@ -186,6 +190,7 @@ regalloc_1(RegAllocMod, CFG0, SpillIndex0, SpillLimit, Target, Options,
Coloring = SpillColors ++ PartColoring,
?ASSERT(begin
+ AllPrecoloured = Target:all_precoloured(),
MaxPhys = lists:max(AllPrecoloured) + 1,
Unused = unused(live_pseudos(Seen, SpillMap, MaxPhys),
SpillMap, CFG0, Target),