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authorBjörn Gustavsson <[email protected]>2017-10-06 09:06:24 +0200
committerBjörn Gustavsson <[email protected]>2017-10-11 09:59:41 +0200
commit34c8b06de52ac81e2938e93ed7a219d7611c16f9 (patch)
tree0ed2df8a4aa99368ee5bf483c056cf808d34fd25 /lib/hipe/icode/hipe_beam_to_icode.erl
parent4fe3f3b8be4825726fab6d4ea7515adf5b5df1ac (diff)
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Optimize try/catch that ignores the return value
If a try/catch is used to ignore the potential exception caused by some expression with a side effect such as: try side_effect() catch _Class:_Reason -> ok end, . . . the generated code will be wasteful: try YReg TryLabel %% call side_effect() here try_end Yreg jump GoodLabel TryLabel: try_case YReg %% try_case has set up registers as follows: %% x(0) -> error | exit | throw %% x(1) -> reason %% x(2) -> raw stack trace data GoodLabel: %% This code does not use any x registers. There will be two code paths that both end up at GoodLabel, and the try_case instruction will set up registers that are never used. We can do better by replacing try_case with try_end to obtain this code: try YReg TryLabel %% call side_effect() here try_end Yreg jump GoodLabel TryLabel: try_end YReg GoodLabel: The jump optimizer (beam_jump) can further optimize this code like this: try YReg TryLabel %% call side_effect() here TryLabel: try_end YReg
Diffstat (limited to 'lib/hipe/icode/hipe_beam_to_icode.erl')
-rw-r--r--lib/hipe/icode/hipe_beam_to_icode.erl6
1 files changed, 6 insertions, 0 deletions
diff --git a/lib/hipe/icode/hipe_beam_to_icode.erl b/lib/hipe/icode/hipe_beam_to_icode.erl
index 2abecf7f18..167f5c67bb 100644
--- a/lib/hipe/icode/hipe_beam_to_icode.erl
+++ b/lib/hipe/icode/hipe_beam_to_icode.erl
@@ -2296,6 +2296,12 @@ split_code([First|Code], Label, Instr) ->
split_code([Instr|Code], Label, Instr, Prev, As) when Prev =:= Label ->
split_code_final(Code, As); % drop both label and instruction
+split_code([{icode_end_try}|_]=Code, Label, {try_case,_}, Prev, As)
+ when Prev =:= Label ->
+ %% The try_case has been replaced with try_end as an optimization.
+ %% Keep this instruction, since it might be the only try_end instruction
+ %% for this try/catch block.
+ split_code_final(Code, As); % drop label
split_code([Other|_Code], Label, Instr, Prev, _As) when Prev =:= Label ->
?EXIT({missing_instr_after_label, Label, Instr, [Other, Prev | _As]});
split_code([Other|Code], Label, Instr, Prev, As) ->