aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
-rw-r--r--lib/hipe/icode/hipe_icode.erl13
-rw-r--r--lib/hipe/rtl/hipe_rtl.erl19
-rw-r--r--lib/hipe/ssa/hipe_ssa.inc22
3 files changed, 43 insertions, 11 deletions
diff --git a/lib/hipe/icode/hipe_icode.erl b/lib/hipe/icode/hipe_icode.erl
index 78508dff22..dce2fcb392 100644
--- a/lib/hipe/icode/hipe_icode.erl
+++ b/lib/hipe/icode/hipe_icode.erl
@@ -594,6 +594,7 @@
uses/1,
defines/1,
is_safe/1,
+ reduce_unused/1,
strip_comments/1,
subst/2,
subst_uses/2,
@@ -1765,6 +1766,18 @@ is_safe(Instr) ->
#icode_end_try{} -> false
end.
+%% @doc Produces a simplified instruction sequence that is equivalent to [Instr]
+%% under the assumption that all results of Instr are unused, or 'false' if
+%% there is no such sequence (other than [Instr] itself).
+
+-spec reduce_unused(icode_instr()) -> false | [icode_instr()].
+
+reduce_unused(Instr) ->
+ case is_safe(Instr) of
+ true -> [];
+ false -> false
+ end.
+
%%-----------------------------------------------------------------------
-spec highest_var(icode_instrs()) -> non_neg_integer().
diff --git a/lib/hipe/rtl/hipe_rtl.erl b/lib/hipe/rtl/hipe_rtl.erl
index e4e857ec43..d39969a0ed 100644
--- a/lib/hipe/rtl/hipe_rtl.erl
+++ b/lib/hipe/rtl/hipe_rtl.erl
@@ -334,6 +334,7 @@
defines/1,
redirect_jmp/3,
is_safe/1,
+ reduce_unused/1,
%% highest_var/1,
pp/1,
pp/2,
@@ -1314,6 +1315,24 @@ is_safe(Instr) ->
#switch{} -> false %% Maybe this is safe...
end.
+%% @spec reduce_unused(rtl_instruction())
+%% -> false | [rtl_instruction()].
+%%
+%% @doc Produces a simplified instruction sequence that is equivalent to [Instr]
+%% under the assumption that all results of Instr are unused, or 'false' if
+%% there is no such sequence (other than [Instr] itself).
+
+reduce_unused(Instr) ->
+ case Instr of
+ #alub{dst=Dst} when Dst =/= [] ->
+ [Instr#alub{dst=[]}];
+ _ ->
+ case is_safe(Instr) of
+ true -> [];
+ false -> false
+ end
+ end.
+
%%
%% True if argument is an alu-operator
%%
diff --git a/lib/hipe/ssa/hipe_ssa.inc b/lib/hipe/ssa/hipe_ssa.inc
index 83ab320306..b511bb6f25 100644
--- a/lib/hipe/ssa/hipe_ssa.inc
+++ b/lib/hipe/ssa/hipe_ssa.inc
@@ -1,4 +1,4 @@
-%% -*- erlang-indent-level: 2 -*-
+%% -*- mode: erlang; erlang-indent-level: 2 -*-
%%
%% %CopyrightBegin%
%%
@@ -943,9 +943,9 @@ do_code([Instr|Instrs], LiveOut, Changed, Acc) ->
false ->
do_code(Instrs, LiveIn, Changed, [Instr|Acc]);
true ->
- case ?CODE:is_safe(Instr) of
+ case ?CODE:is_call(Instr) of
true ->
- case ?CODE:is_call(Instr) of
+ case ?CODE:is_safe(Instr) of
true ->
case ?CODE:call_continuation(Instr) of
[] ->
@@ -955,11 +955,6 @@ do_code([Instr|Instrs], LiveOut, Changed, Acc) ->
do_code(Instrs, LiveOut, true, [NewInstr|Acc])
end;
false ->
- do_code(Instrs, LiveOut, true, Acc)
- end;
- false -> %% not a safe instruction - cannot be removed
- case ?CODE:is_call(Instr) of
- true ->
case ?CODE:call_dstlist(Instr) of
[] -> %% result was not used anyway; no change
do_code(Instrs, LiveIn, Changed, [Instr|Acc]);
@@ -968,9 +963,14 @@ do_code([Instr|Instrs], LiveOut, Changed, Acc) ->
do_code(Instrs, LiveIn, true, [NewInstr|Acc]);
[_|_] -> %% calls with multiple dests are left untouched
do_code(Instrs, LiveIn, Changed, [Instr|Acc])
- end;
- false ->
- do_code(Instrs, LiveIn, Changed, [Instr|Acc])
+ end
+ end;
+ false ->
+ case ?CODE:reduce_unused(Instr) of
+ false -> % not a safe instruction - cannot be removed
+ do_code(Instrs, LiveIn, Changed, [Instr|Acc]);
+ Replacement ->
+ do_code(lists:reverse(Replacement, Instrs), LiveOut, true, Acc)
end
end
end;