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authorMagnus Lång <[email protected]>2016-09-24 09:42:01 +0200
committerMagnus Lång <[email protected]>2016-11-15 14:59:00 +0100
commitdf04801d5585f52ddc042d30873bdc95da019af6 (patch)
treeb803d4b450ffbde43bac39ac2375f9c23971ce5f /lib/hipe/x86
parent35f74834dc4130c613fea2a5483ba02ed43af2c4 (diff)
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hipe_x86: LeaToAdd peephole rule
Although LEA is useful for three-address form adds, sometimes it is used where a normal add would have sufficed (due to the addition being the last use of one of the operands; but RTL lowering does not know that as it does not have liveness information). As a workaround, we convert LEA back to ADD when the destination is the same as one of the operands.
Diffstat (limited to 'lib/hipe/x86')
-rw-r--r--lib/hipe/x86/hipe_x86_postpass.erl12
1 files changed, 12 insertions, 0 deletions
diff --git a/lib/hipe/x86/hipe_x86_postpass.erl b/lib/hipe/x86/hipe_x86_postpass.erl
index bd232041b6..390f5bf5e7 100644
--- a/lib/hipe/x86/hipe_x86_postpass.erl
+++ b/lib/hipe/x86/hipe_x86_postpass.erl
@@ -183,6 +183,18 @@ peep([B = #alu{aluop=Op,src=#x86_imm{value=Val},dst=Dst}|Insns], Res, Lst) ->
peep(Insns, [B|Res], Lst)
end;
+%% LeaToAdd
+%% This rule transforms lea into add when the destination is the same as one of
+%% the operands. Sound because lea is never used where the condition codes are
+%% live (and would be clobbered by add).
+%% ----------
+peep([#lea{mem=#x86_mem{base=#x86_temp{reg=DstR},off=Src},
+ temp=Dst=#x86_temp{reg=DstR}}|Insns], Res, Lst) ->
+ peep(Insns, [#alu{aluop='add',src=Src,dst=Dst}|Res], [leaToAdd|Lst]);
+peep([#lea{mem=#x86_mem{base=Src,off=#x86_temp{reg=DstR}},
+ temp=Dst=#x86_temp{reg=DstR}}|Insns], Res, Lst) ->
+ peep(Insns, [#alu{aluop='add',src=Src,dst=Dst}|Res], [leaToAdd|Lst]);
+
%% SubToDec
%% This rule turns "subl $1,Dst; jl Lab" into "decl Dst; jl Lab", which
%% changes reduction counter tests to use decl instead of subl.