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2016-08-05beam_block: Fix potentially unsafe optimization in move_allocates/1Björn Gustavsson
beam_block has an optimization that only is safe when it is applied immediately after code generation. That is pointed out in a comment: NOTE: Moving allocation instructions is only safe because it is done immediately after code generation so that we KNOW that if {x,X} is initialized, all x registers with lower numbers are also initialized. That assumption may not be true after other optimizations, such as the beam_utils:live_opt/1 optimization. The new beam_reorder pass added in OTP 19 runs before beam_block. Therefore, the optimization is potentially unsafe. The optimization is also unsafe if compilation is started from assembly code in a .S file. Rewrite the optimization to make it safe. See the newly added comment for details. ERL-202
2016-06-01beam_block: Eliminate crash in beam_utilsBjörn Gustavsson
Somewhat simplified, beam_block would rewrite the target for the first instruction in this code sequence: move x(0) => y(1) gc_bif '+' 1 x(0) => y(0) move y(1) => x(1) move nil => x(0) call 2 local_function/2 The resulting code would be: move x(0) => x(1) %% Changed target. gc_bif '+' 1 x(0) => y(0) move x(1) => y(1) %% Operands swapped (see 02d6135813). move nil => x(0) call 2 local_function/2 The resulting code is not safe because the x(1) will be killed by the gc_bif instruction. 7a47b20c3a cleaned up move optimizations and would reject the optimization if the target was an X register and an allocating instruction was found. To avoid this bug, the optimization must be rejected even if the target is a Y register.
2016-04-13Merge branch 'henrik/update-copyrightyear'Henrik Nord
* henrik/update-copyrightyear: update copyright-year
2016-04-08Remove unreachable code after 'raise' instructionsBjörn Gustavsson
Remove the unreachable instructions after a 'raise' instruction (e.g. a 'jump' or 'deallocate', 'return') to decrease code size.
2016-03-15update copyright-yearHenrik Nord
2016-03-10beam_block: Eliminate unsafe optimizationBjörn Gustavsson
Consider this code: %% Start of block get_tuple_element Tuple 0 Element get_map_elements Fail Map [Key => Dest] . . . move Element UltimateDest %% End of block Fail: %% Code that uses Element. beam_block (more precisely, otp_tuple_element/1) would incorrectly transform the code to this: %% Start of block get_map_elements Fail Map [Key => Dest] . . . get_tuple_element Tuple 0 UltimateDest %% End of block Fail: %% Code that uses Element. That is, the code at label Fail would use register Element, which is either uninitalized or contains the wrong value. We could fix this problem by always keeping label information at hand when optimizing blocks so that we could check the code at the failure label for get_map_elements. That would require changes to beam_block and beam_utils. We might consider doing that in the future if it turns out be worth it. For now, I have decided that I want to keep the simplicity of blocks (allowing them to be optimized without keeping label information). That could be achieved by not including get_map_elements in blocks. Another way, which I have chosen, is to only allow get_map_elements as the first instruction in the block. For background on the bug: c288ab8 introduced the beam_reorder pass and 5f431276 introduced opt_tuple_element() in beam_block.
2015-09-28beam_type: Improve optimizations by keeping track of booleansBjörn Gustavsson
There is an optimization in beam_block to simplify a select_val on a known boolean value. We can implement this optimization in a cleaner way in beam_type and it will also be applicable in more situations. (When I added the optimization to beam_type without removing the optimization from beam_block, the optimization was applied 66 times.)
2015-09-28Move out bit syntax optimizations from beam_blockBjörn Gustavsson
In the future we might want to add more bit syntax optimizations, but beam_block is already sufficiently complicated. Therefore, move the bit syntax optimizations out of beam_block into a separate compiler pass called beam_bs.
2015-09-21Regain full coverage of beam_blockBjörn Gustavsson
d0784035ab fixed a problem with register corruption. Because of that, opt_moves/2 will never be asked to optimize instructions with more than two destination registers. Therefore, to regain full coverage of beam_block, remove the final clause in opt_moves/2.
2015-09-07Merge branch 'maint'Björn-Egil Dahlberg
2015-09-04compiler: Fix get_map_elements register corruptionBjörn-Egil Dahlberg
Instruction get_map_elements might destroy target registers when the fail-label is taken. Only seen for patterns with two, and only two, target registers. Specifically: we copy one register, and then jump. foo(A,#{a := V1, b := V2}) -> ... foo(A,#{b := V}) -> ... call foo(value, #{a=>whops, c=>42}). corresponding assembler: {test,is_map,{f,5},[{x,1}]}. {get_map_elements,{f,7},{x,1},{list,[{atom,a},{x,1},{atom,b},{x,2}]}}. %% if 'a' exists but not 'b' {x,1} is overwritten, jump {f,7} {move,{integer,1},{x,0}}. {call_only,3,{f,10}}. {label,7}. {get_map_elements,{f,8},{x,1},{list,[{atom,b},{x,2}]}}. %% {x,1} (src) is read with a corrupt value {move,{x,0},{x,1}}. {move,{integer,2},{x,0}}. {call_only,3,{f,10}}. The fix is to remove 'opt_moves' pass for get_map_elements instruction in the case of two or more destinations. Reported-by: Valery Tikhonov
2015-08-21beam_validator: Don't allow x(1023) to be usedBjörn Gustavsson
In 45f469ca0890, the BEAM loader started to use x(1023) as scratch register for some instructions. Therefore we should not allow x(1023) to be used in code emitted by the compiler.
2015-08-21Put 'try' in blocks to optimize allocation instructionsBjörn Gustavsson
Put 'try' instructions inside block to improve the optimization of allocation instructions. Currently, the compiler only looks at initialization of y registers inside blocks when determining which y registers that will be "naturally" initialized.
2015-08-21Optimize get_tuple_element instructions by moving them forwardBjörn Gustavsson
2015-08-21beam_block: Improve the move optimizationsBjörn Gustavsson
Here is an example of a move instruction that could not be optimized away because the {x,2} register was not killed: get_tuple_element Reg Pos {x,2} . . . move {x,2} {y,0} put_list {x,2} nil Any We can do the optimization if we replace all occurrences of the {x,2} register as a source with {y,0}: get_tuple_element Reg Pos {y,0} . . . put_list {y,0} nil Dst
2015-08-21beam_block: Clean up optimization of move optimizationsBjörn Gustavsson
The 'move' optimization was relatively clean until GC BIFs were introduced. Instead of re-thinking the implementation, the existing code was fixed and patched. The current code unsuccessfully attempts to eliminate 'move' instructions across GC BIF and allocation instructions. We can simplify the code if we give up as soon as we encounter any instruction that allocates.
2015-08-21beam_block: Eliminate redundant wasteful call to opt/1Björn Gustavsson
opt_alloc/1 makes a redundant call to opt/1. It is redundant because the opt/1 function has already been applied to the instruction sequence prior to calling opt_alloc/1.
2015-06-18Change license text to APLv2Bruce Yinhe
2015-04-22v3_codegen: Reduce cost for fixing up bs_match_string instructionsBjörn Gustavsson
Commit b76588fb5a introduced an optimization of the compile time of huge functions with many bs_match_string instructions. The optimization is done in two passes. The first pass coalesces adjacent bs_match_string instructions. To avoid copying bitstrings multiple times, the bitstrings in the instructions are combined in to a (deep) list. The second pass goes through all instructions in the function and combines the list of bitstrings to a single bitstring in all bs_match_string instructions. The second pass (fix_bs_match_string) is run on all instructions in each function, even if there are no bs_match_instructions in the function. While fix_bs_match_string is not a bottleneck (it is a linear pass), its execution time is noticeable when profiling some modules. Move the execution of the second pass to the select_binary() function so that it will only be executed for instructions that do binary matching. Also take the opportunity to optimize away uses of bs_restore2 that occour directly after a bs_save2. That optimimization is currently done in beam_block, but it can be done essentially for free in the same pass that fixes up bs_match_string instructions.
2015-03-09sys_core_fold: Improve optimization of 'not'Björn Gustavsson
Optimize away 'not' in sys_core_fold instead of in beam_block and beam_dead, as we can do a better job in sys_core_fold. I modified the test suite temporarily to never turn off Core Erlang modifications and looked at the coverage. With the new optimizations active in sys_core_fold, the code in beam_block and beam_dead did not find a single 'not' that it could optimize. That proves that the new optimization is at least as good as the old one. Manually, I could also verify that the new optimization would optimize some variations of 'not' that the old one would not handle.
2015-03-09Introduce '%live' annotations with a complete register mapBjörn Gustavsson
As a preparation for fixing a bug, introduce a complete register map in the '%live' annotations.
2015-01-12compiler: Rename util function to adhere to name policyBjörn-Egil Dahlberg
* beam_utils:joineven/1 -> beam_utils:join_even/1 * beam_utils:split_even/1 -> beam_utils:split_even/1
2014-08-26compiler: Use variables in Map beam assmeblerBjörn-Egil Dahlberg
2014-02-13compiler: Change map instructions for fetching valuesBjörn-Egil Dahlberg
* Combine multiple get values with one instruction * Combine multiple check keys with one instruction
2014-01-28compiler: Fix get_map_element bug with allocateBjörn-Egil Dahlberg
The instruction get_map_element has a faillabel so you may not use the instruction within a allocate/deallocate block.
2014-01-28compiler: Implement different instructions for => and :=Björn Gustavsson
2014-01-28Implement support for maps in the compilerBjörn Gustavsson
To make it possible to build the entire OTP system, also define dummys for the instructions in ops.tab.
2013-12-13Collect all optimised allocate instructions in beam_blockAnthony Ramine
Any init instruction following an allocate is put in the Inits list of the corresponding alloc tuple.
2013-12-13Properly collect allocate_zero instructions in beam_blockAnthony Ramine
If an allocate_zero instruction is fed to beam_block and the beam_type pass is not used afterwards (e.g. with erlc +no_topt), the 'no_opt' atom will be rejected by beam_flatten.
2013-12-13Properly let floating-point instructions through in the BEAM compilerAnthony Ramine
The compiler shouldn't crash when fed an already-optimised BEAM assembly file.
2013-01-25Update copyright yearsBjörn-Egil Dahlberg
2012-10-10Rewrite select_val and select_tuple_arity to a select instructionBjörn Gustavsson
Eliminate some code bloat.
2012-10-09Rewrite bs_put* instructions to a generic bs_put instructionBjörn Gustavsson
Seven bs_put_* instructions can be combined into one generic bs_put instruction to avoid some code bloat. That will also improve some optimizations (such as beam_trim) that did not handle all bs_put* variants.
2012-10-09Refactor removal of unused labelsBjörn Gustavsson
Since we always want to remove unused labels directly after code generation (whether we'll run the optimization passes or not), we can simplify the code by doing it in beam_a.
2012-10-09v3_codegen: Combine adjacent bs_match_string instructionsBjörn Gustavsson
In modules with huge functions with many bs_match_string instructions, we can speed up the compilation by combining adjacent bs_match_strings instruction in v3_codegen (as opposed to in beam_block where we used to do it). For instance, on my computer the v3_codegen became more than twice as fast when compiling the re_testoutput1_split_test module in the STDLIB test suites.
2011-12-09Update copyright yearsBjörn-Egil Dahlberg
2011-08-16compiler: Generate line instructionsBjörn Gustavsson
2010-10-12beam_block: Do optimizations in the safe orderBjörn Gustavsson
Moving of allocation instructions upwards in the instruction stream (in order to enable further optimizations) in beam_block, is implemented with the assumption that if a register {x,X} contains a valid term, then all other x register with lower numbers than X also contain valid terms. That assumption is true after code generation. The beam_utils:live_opt/1 optimization, however, may invalidate that assumption. For instance, if a receive statement exports a variable that is used, but the return value of the receive statement is not used, then {x,1} but not {x,0} contains a valid term at the end of the receive statement. If the receive statement is followed by {bif,self,{f,0},[],{x,0}}. {test_heap,NumberOfWords,2}. moving the allocation upwards will produce {test_heap,NumberOfWords,2}. {bif,self,{f,0},[],{x,0}}. which will cause the beam_validator pass to scream loudly that {x,0} is not live at the test_heap instruction. Fix the problem by doing the optimizations in reverse order. Reported-by: Jim Engquist
2010-05-20beam_block: Remove a clause that will never be executedBjörn Gustavsson
Since the introduction of literals in R12B, empty tuples are literals. Thus the put_tuple/2 instruction is always followed by at least one put/1 instruction. Therefore the alloc_may_pass/1 function in beam_block no longer needs a clause for for "put_tuple", because the clause for "put" will always be reached first (since the instruction stream is scanned in reverse execution order). Note that if the compiler would generate a "put_tuple 0 Dst" instruction for some unfathomable reason, we should still be because the run-time system will now refuse to load a module containing such an instruction.
2010-03-25Merge branch 'bg/compiler-remove-r11-support' into devErlang/OTP
* bg/compiler-remove-r11-support: compiler: Don't support the no_binaries option erts: Don't support the put_string/3 instruction compiler: Don't support the no_constant_pool option compiler: Don't support the r11 option test_server: Don't support communication with R11 nodes binary_SUITE: Don't test bit-level binary roundtrips with R11 nodes erts: Test compatibility of funs with R12 instead of R11 OTP-8531 bg/compiler-remove-r11-support
2010-03-22compiler: Don't support the no_constant_pool optionBjörn Gustavsson
The no_constant_pool option was implied by the r11 option. It turns off the usage of the constant (literal) pool, so that BEAM instructions that use constants can be loaded in an R11 system. Since the r11 option has been removed, there is no need to retain the no_constant_pool option.
2009-11-20The R13B03 release.OTP_R13B03Erlang/OTP