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2018-08-24Introduce a new SSA-based intermediate formatBjörn Gustavsson
v3_codegen is replaced by three new passes: * beam_kernel_to_ssa which translates the Kernel Erlang format to a new SSA-based intermediate format. * beam_ssa_pre_codegen which prepares the SSA-based format for code generation, including register allocation. Registers are allocated using the linear scan algorithm. * beam_ssa_codegen which generates BEAM assembly code from the SSA-based format. It easier and more effective to optimize the SSA-based format before X and Y registers have been assigned. The current optimization passes constantly have to make sure no "holes" in the X register assignments are created (that is, that no X register becomes undefined that an allocation instruction depends on). This commit also introduces the following optimizations: * Replacing of tuple matching of records with the is_tagged_tuple instruction. (Replacing beam_record.) * Sinking of get_tuple_element instructions to just before the first use of the extracted values. As well as potentially avoiding extracting tuple elements when they are not actually used on all executions paths, this optimization could also reduce the number values that will need to be stored in Y registers. (Similar to beam_reorder, but more effective.) * Live optimizations, removing the definition of a variable that is not subsequently used (provided that the operation has no side effects), as well strength reduction of binary matching by replacing the extraction of value from a binary with a skip instruction. (Used to be done by beam_block, beam_utils, and v3_codegen.) * Removal of redundant bs_restore2 instructions. (Formerly done by beam_bs.) * Type-based optimizations across branches. More effective than the old beam_type pass that only did type-based optimizations in basic blocks. * Optimization of floating point instructions. (Formerly done by beam_type.) * Optimization of receive statements to introduce recv_mark and recv_set instructions. More effective with far fewer restrictions on what instructions are allowed between creating the reference and entering the receive statement. * Common subexpression elimination. (Formerly done by beam_block.)
2013-04-19Use a set to store ref registers in beam_receiveAnthony Ramine
In some circumstances, as when inlining code, when some optimization passes are disabled or with hand-written but semantically correct Core Erlang or BEAM assembly, a fresh reference may be live in more than one register: ... {allocate_zero,2,2}. ... {call_ext,0,{extfunc,erlang,make_ref,0}}. % Ref in [x0] ... {move,{x,0},{y,0}}. % Ref in [x0,y0] {move,{y,1},{x,0}}. % Ref in [y0] ... {move,{y,0},{x,0}}. % Ref in [x0,y0] {move,{x,0},{y,1}}. % Ref in [x0,y0,y1] {label,5}. {loop_rec,{f,6},{x,0}}. % Ref in [y0,y1] ... {loop_rec_end,{f,5}}. {label,6}. {wait,{f,5}}. ... Pass beam_receive expects a single live register for the ref when it encounters the loop_rec instruction and crashes with the following reason: $ erlc t.S ... crash reason: {{case_clause, {'EXIT', {{case_clause,[{y,1},{y,0}]}, [{beam_receive,opt_recv,5, [{file,"beam_receive.erl"},{line,154}]}, ...]}}}, ...} This commit teaches beam_receive how to use a set of registers instead of a single one when tracking fresh references, thus avoiding the crash.
2013-04-05Use erlang:demonitor(Ref, [flush]) where applicableLoïc Hoguin
2012-10-09beam_receive: Optimize receives using refs created by spawn_monitor/{1,3}Björn Gustavsson
2012-10-09beam_jump: Don't move a block which can be entered via a fallthroughBjörn Gustavsson
beam_jump moves short code sequences ending in an instruction that causes an exception to the end of the function, in the hope that a jump around the moved blocked can be replaced with a fallthrough. Therefore, moving a block that is entered via a fallthrough defeats the purpose of the optimization. Also add two more test cases for the beam_receive module to ensure that all lines are still covered.
2010-05-11compiler test: Test optimization of receive statementsBjörn Gustavsson
We don't attempt to run the generated code, but use beam_disasm and check for the presence or absence (as appropriate) of the recv_mark/1 and recv_set/1 instructions.