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diff --git a/docs/users_guide/debugging.rst b/docs/users_guide/debugging.rst index bc155884c8..6a4c7fe1a7 100644 --- a/docs/users_guide/debugging.rst +++ b/docs/users_guide/debugging.rst @@ -6,8 +6,14 @@ Debugging the compiler .. index:: single: debugging options (for GHC) +.. + It is not necessary to provide :category: tags for ``ghc-flag:``s defined in + this file; a default is specified in ``flags.py``. + HACKER TERRITORY. HACKER TERRITORY. (You were warned.) +.. contents:: Dump flags + .. _dumping-output: Dumping out compiler intermediate structures @@ -17,255 +23,552 @@ Dumping out compiler intermediate structures single: dumping GHC intermediates single: intermediate passes, output -``-ddump-`` ⟨pass⟩ - .. index:: - single: -ddump options +.. ghc-flag:: -ddump-to-file + :shortdesc: Dump to files instead of stdout + :type: dynamic - Make a debugging dump after pass ``<pass>`` (may be common enough to - need a short form…). You can get all of these at once (*lots* of - output) by using ``-v5``, or most of them with ``-v4``. You can - prevent them from clogging up your standard output by passing - :ghc-flag:`-ddump-to-file`. Some of the most useful ones are: + Causes the output from all of the flags listed below to be dumped + to a file. The file name depends upon the output produced; for instance, + output from :ghc-flag:`-ddump-simpl` will end up in + :file:`{module}.dump-simpl`. - .. ghc-flag:: -ddump-to-file +.. ghc-flag:: -ddump-json + :shortdesc: Dump error messages as JSON documents + :type: dynamic - Causes the output from all of the flags listed below to be dumped - to a file. The file name depends upon the output produced; for instance, - output from :ghc-flag:`-ddump-simpl` will end up in - :file:`{module}.dump-simpl`. + Dump error messages as JSON documents. This is intended to be consumed + by external tooling. A good way to use it is in conjunction with + :ghc-flag:`-ddump-to-file`. - .. ghc-flag:: -ddump-parsed +.. ghc-flag:: -dshow-passes + :shortdesc: Print out each pass name as it happens + :type: dynamic - Dump parser output + Print out each pass name, its runtime and heap allocations as it happens. + Note that this may come at a slight performance cost as the compiler will + be a bit more eager in forcing pass results to more accurately account for + their costs. - .. ghc-flag:: -ddump-parsed-ast + Two types of messages are produced: Those beginning with ``***`` do + denote the beginning of a compilation phase whereas those starting with + ``!!!`` mark the end of a pass and are accompanied by allocation and + runtime statistics. - Dump parser output as a syntax tree +.. ghc-flag:: -dfaststring-stats + :shortdesc: Show statistics for fast string usage when finished + :type: dynamic - .. ghc-flag:: -ddump-rn + Show statistics on the usage of fast strings by the compiler. - Dump renamer output +.. ghc-flag:: -dppr-debug + :shortdesc: Turn on debug printing (more verbose) + :type: dynamic - .. ghc-flag:: -ddump-rn-ast + Debugging output is in one of several "styles." Take the printing of + types, for example. In the "user" style (the default), the + compiler's internal ideas about types are presented in Haskell + source-level syntax, insofar as possible. In the "debug" style + (which is the default for debugging output), the types are printed + in with explicit foralls, and variables have their unique-id + attached (so you can check for things that look the same but + aren't). This flag makes debugging output appear in the more verbose + debug style. - Dump renamer output as a syntax tree +.. ghc-flag:: -ddump-timings + :shortdesc: Dump per-pass timing and allocation statistics + :type: dynamic - .. ghc-flag:: -ddump-tc + Show allocation and runtime statistics for various stages of compilation. - Dump typechecker output +GHC is a large program consisting of a number of stages. You can tell GHC to +dump information from various stages of compilation using the ``-ddump-⟨pass⟩`` +flags listed below. Note that some of these tend to produce a lot of output. +You can prevent them from clogging up your standard output by passing +:ghc-flag:`-ddump-to-file`. - .. ghc-flag:: -ddump-tc-ast +Front-end +~~~~~~~~~ - Dump typechecker output as a syntax tree +These flags dump various information from GHC's frontend. This includes the +parser and interface file reader. - .. ghc-flag:: -ddump-splices +.. ghc-flag:: -ddump-parsed + :shortdesc: Dump parse tree + :type: dynamic - Dump Template Haskell expressions that we splice in, and what - Haskell code the expression evaluates to. + Dump parser output - .. ghc-flag:: -dth-dec-file=⟨file⟩ +.. ghc-flag:: -ddump-parsed-ast + :shortdesc: Dump parser output as a syntax tree + :type: dynamic - Dump expansions of all top-level Template Haskell splices into ⟨file⟩. + Dump parser output as a syntax tree - .. ghc-flag:: -ddump-types +.. ghc-flag:: -ddump-if-trace + :shortdesc: Trace interface files + :type: dynamic - Dump a type signature for each value defined at the top level of - the module. The list is sorted alphabetically. Using - :ghc-flag:`-dppr-debug` dumps a type signature for all the imported and - system-defined things as well; useful for debugging the - compiler. + Make the interface loader be *real* chatty about what it is up to. - .. ghc-flag:: -ddump-deriv - Dump derived instances +Type-checking and renaming +~~~~~~~~~~~~~~~~~~~~~~~~~~ - .. ghc-flag:: -ddump-ds +These flags dump various information from GHC's typechecker and renamer. - Dump desugarer output +.. ghc-flag:: -ddump-tc-trace + :shortdesc: Trace typechecker + :type: dynamic - .. ghc-flag:: -ddump-spec + Make the type checker be *real* chatty about what it is up to. - Dump output of specialisation pass +.. ghc-flag:: -ddump-rn-trace + :shortdesc: Trace renamer + :type: dynamic - .. ghc-flag:: -ddump-rules + Make the renamer be *real* chatty about what it is up to. - Dumps all rewrite rules specified in this module; see - :ref:`controlling-rules`. +.. ghc-flag:: -ddump-ec-trace + :shortdesc: Trace exhaustiveness checker + :type: dynamic - .. ghc-flag:: -ddump-rule-firings + Make the pattern match exhaustiveness checker be *real* chatty about + what it is up to. - Dumps the names of all rules that fired in this module +.. ghc-flag:: -ddump-rn-stats + :shortdesc: Renamer stats + :type: dynamic - .. ghc-flag:: -ddump-rule-rewrites + Print out summary of what kind of information the renamer had to + bring in. - Dumps detailed information about all rules that fired in this - module +.. ghc-flag:: -ddump-rn + :shortdesc: Dump renamer output + :type: dynamic - .. ghc-flag:: -ddump-vect + Dump renamer output - Dumps the output of the vectoriser. +.. ghc-flag:: -ddump-rn-ast + :shortdesc: Dump renamer output as a syntax tree + :type: dynamic - .. ghc-flag:: -ddump-simpl + Dump renamer output as a syntax tree - Dump simplifier output (Core-to-Core passes) +.. ghc-flag:: -ddump-tc + :shortdesc: Dump typechecker output + :type: dynamic - .. ghc-flag:: -ddump-inlinings + Dump typechecker output. Note that this hides a great deal of detail by + default; you might consider using this with + :ghc-flag:`-fprint-typechecker-elaboration`. - Dumps inlining info from the simplifier. Note that if used in conjunction with - :ghc-flag:`-dverbose-core2core` the compiler will also dump the inlinings that - it considers but passes up, along with its rationale. +.. ghc-flag:: -ddump-tc-ast + :shortdesc: Dump typechecker output as a syntax tree + :type: dynamic - .. ghc-flag:: -ddump-stranal + Dump typechecker output as a syntax tree - Dump strictness analyser output +.. ghc-flag:: -ddump-splices + :shortdesc: Dump TH spliced expressions, and what they evaluate to + :type: dynamic - .. ghc-flag:: -ddump-str-signatures + Dump Template Haskell expressions that we splice in, and what + Haskell code the expression evaluates to. - Dump strictness signatures +.. ghc-flag:: -dth-dec-file + :shortdesc: Dump evaluated TH declarations into `*.th.hs` files + :type: dynamic - .. ghc-flag:: -ddump-cse + Dump expansions of all top-level Template Haskell splices into + :file:`{module}.th.hs` for each file :file:`{module}.hs`. - Dump common subexpression elimination (CSE) pass output +.. ghc-flag:: -ddump-types + :shortdesc: Dump type signatures + :type: dynamic - .. ghc-flag:: -ddump-worker-wrapper + Dump a type signature for each value defined at the top level of + the module. The list is sorted alphabetically. Using + :ghc-flag:`-dppr-debug` dumps a type signature for all the imported and + system-defined things as well; useful for debugging the + compiler. - Dump worker/wrapper split output +.. ghc-flag:: -ddump-deriv + :shortdesc: Dump deriving output + :type: dynamic - .. ghc-flag:: -ddump-occur-anal + Dump derived instances - Dump "occurrence analysis" output - .. ghc-flag:: -ddump-prep +Core representation and simplification +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - Dump output of Core preparation pass +These flags dump various phases of GHC's Core-to-Core pipeline. This begins with +the desugarer and includes the simplifier, worker-wrapper transformation, the +rule engine, the specialiser, the strictness/occurrence analyser, and a common +subexpression elimination pass. - .. ghc-flag:: -ddump-stg +.. ghc-flag:: -ddump-core-stats + :shortdesc: Print a one-line summary of the size of the Core program at the + end of the optimisation pipeline + :type: dynamic - Dump output of STG-to-STG passes + Print a one-line summary of the size of the Core program at the end + of the optimisation pipeline. - .. ghc-flag:: -ddump-cmm +.. ghc-flag:: -ddump-ds + -ddump-ds-preopt + :shortdesc: Dump desugarer output. + :type: dynamic - Dump the result of the C-- pipeline processing + Dump desugarer output. :ghc-flag:`-ddump-ds` dumps the output after the very + simple optimiser has run (which discards a lot of clutter and hence is a + sensible default. :ghc-flag:`-ddump-ds-preopt` shows the output after + desugaring but before the very simple optimiser. - .. ghc-flag:: -ddump-cmm-from-stg - Dump the result of STG-to-C-- conversion +.. ghc-flag:: -ddump-simpl-iterations + :shortdesc: Dump output from each simplifier iteration + :type: dynamic - .. ghc-flag:: -ddump-cmm-verbose + Show the output of each *iteration* of the simplifier (each run of + the simplifier has a maximum number of iterations, normally 4). - Dump output from all C-- pipeline stages. In case of - ``.cmm`` compilation this also dumps the result of - file parsing. +.. ghc-flag:: -ddump-simpl-stats + :shortdesc: Dump simplifier stats + :type: dynamic - .. ghc-flag:: -ddump-opt-cmm + Dump statistics about how many of each kind of transformation took + place. If you add :ghc-flag:`-dppr-debug` you get more detailed information. - Dump the results of C-- to C-- optimising passes. +.. ghc-flag:: -dverbose-core2core + :shortdesc: Show output from each core-to-core pass + :type: dynamic - .. ghc-flag:: -ddump-asm + Show the output of the intermediate Core-to-Core pass. (*lots* of output!) + So: when we're really desperate: - Dump assembly language produced by the :ref:`native code - generator <native-code-gen>` + .. code-block:: sh - .. ghc-flag:: -ddump-llvm + % ghc -noC -O -ddump-simpl -dverbose-core2core -dcore-lint Foo.hs - :implies: :ghc-flag:`-fllvm` +.. ghc-flag:: -ddump-spec + :shortdesc: Dump specialiser output + :type: dynamic - LLVM code from the :ref:`LLVM code generator <llvm-code-gen>` + Dump output of specialisation pass - .. ghc-flag:: -ddump-bcos +.. ghc-flag:: -ddump-rules + :shortdesc: Dump rewrite rules + :type: dynamic - Dump byte-code compiler output + Dumps all rewrite rules specified in this module; see + :ref:`controlling-rules`. - .. ghc-flag:: -ddump-foreign +.. ghc-flag:: -ddump-rule-firings + :shortdesc: Dump rule firing info + :type: dynamic - dump foreign export stubs + Dumps the names of all rules that fired in this module - .. ghc-flag:: -ddump-json +.. ghc-flag:: -ddump-rule-rewrites + :shortdesc: Dump detailed rule firing info + :type: dynamic - Dump error messages as JSON documents. This is intended to be consumed - by external tooling. A good way to use it is in conjunction with - :ghc-flag:`-ddump-to-file`. + Dumps detailed information about all rules that fired in this + module -.. ghc-flag:: -ddump-simpl-iterations +.. ghc-flag:: -drule-check=⟨str⟩ + :shortdesc: Dump information about potential rule application + :type: dynamic - Show the output of each *iteration* of the simplifier (each run of - the simplifier has a maximum number of iterations, normally 4). This - outputs even more information than ``-ddump-simpl-phases``. + This flag is useful for debugging why a rule you expect to be firing isn't. -.. ghc-flag:: -ddump-simpl-stats + Rules are filtered by the user provided string, a rule is kept if a prefix + of its name matches the string. + The pass then checks whether any of these rules could apply to + the program but which didn't file for some reason. For example, specifying + ``-drule-check=SPEC`` will check whether there are any applications which + might be subject to a rule created by specialisation. - Dump statistics about how many of each kind of transformation too - place. If you add ``-dppr-debug`` you get more detailed information. +.. ghc-flag:: -dinline-check=⟨str⟩ + :shortdesc: Dump information about inlining decisions + :type: dynamic -.. ghc-flag:: -ddump-if-trace + This flag is useful for debugging why a definition is not inlined. - Make the interface loader be *real* chatty about what it is up to. + When a string is passed to this flag we report information + about all functions whose name shares a prefix with the string. -.. ghc-flag:: -ddump-tc-trace + For example, if you are inspecting the core of your program and you observe + that ``foo`` is not being inlined. You can pass ``-dinline-check foo`` and + you will see a report about why ``foo`` is not inlined. - Make the type checker be *real* chatty about what it is up to. +.. ghc-flag:: -ddump-simpl + :shortdesc: Dump final simplifier output + :type: dynamic -.. ghc-flag:: -ddump-vt-trace + Dump simplifier output (Core-to-Core passes) - Make the vectoriser be *real* chatty about what it is up to. +.. ghc-flag:: -ddump-inlinings + :shortdesc: Dump inlining info + :type: dynamic -.. ghc-flag:: -ddump-rn-trace + Dumps inlining info from the simplifier. Note that if used in + conjunction with :ghc-flag:`-dverbose-core2core` the compiler will + also dump the inlinings that it considers but passes up, along with + its rationale. - Make the renamer be *real* chatty about what it is up to. +.. ghc-flag:: -ddump-stranal + :shortdesc: Dump strictness analyser output + :type: dynamic -.. ghc-flag:: -ddump-ec-trace + Dump strictness analyser output - Make the pattern match exhaustiveness checker be *real* chatty about - what it is up to. +.. ghc-flag:: -ddump-str-signatures + :shortdesc: Dump strictness signatures + :type: dynamic -.. ghc-flag:: -ddump-rn-stats + Dump strictness signatures - Print out summary of what kind of information the renamer had to - bring in. +.. ghc-flag:: -ddump-cse + :shortdesc: Dump CSE output + :type: dynamic -.. ghc-flag:: -dverbose-core2core - -dverbose-stg2stg + Dump common subexpression elimination (CSE) pass output - Show the output of the intermediate Core-to-Core and STG-to-STG - passes, respectively. (*lots* of output!) So: when we're really - desperate: +.. ghc-flag:: -ddump-worker-wrapper + :shortdesc: Dump worker-wrapper output + :type: dynamic - .. code-block:: sh + Dump worker/wrapper split output - % ghc -noC -O -ddump-simpl -dverbose-core2core -dcore-lint Foo.hs +.. ghc-flag:: -ddump-occur-anal + :shortdesc: Dump occurrence analysis output + :type: dynamic -.. ghc-flag:: -dshow-passes + Dump "occurrence analysis" output - Print out each pass name, its runtime and heap allocations as it happens. - Note that this may come at a slight performance cost as the compiler will - be a bit more eager in forcing pass results to more accurately account for - their costs. +.. ghc-flag:: -ddump-prep + :shortdesc: Dump prepared core + :type: dynamic - Two types of messages are produced: Those beginning with ``***`` are - denote the beginning of a compilation phase whereas those starting with - ``!!!`` mark the end of a pass and are accompanied by allocation and - runtime statistics. + Dump output of Core preparation pass -.. ghc-flag:: -ddump-core-stats - Print a one-line summary of the size of the Core program at the end - of the optimisation pipeline. +STG representation +~~~~~~~~~~~~~~~~~~ -.. ghc-flag:: -dfaststring-stats +These flags dump various phases of GHC's STG pipeline. - Show statistics on the usage of fast strings by the compiler. +.. ghc-flag:: -ddump-stg + :shortdesc: Dump final STG + :type: dynamic -.. ghc-flag:: -dppr-debug + Dump output of STG-to-STG passes + +.. ghc-flag:: -dverbose-stg2stg + :shortdesc: Show output from each STG-to-STG pass + :type: dynamic + + Show the output of the intermediate STG-to-STG pass. (*lots* of output!) + + +C-\\- representation +~~~~~~~~~~~~~~~~~~~~ + +These flags dump various phases of GHC's C-\\- pipeline. + +.. ghc-flag:: -ddump-cmm-verbose + :shortdesc: Show output from main C-\\- pipeline passes + :type: dynamic + + Dump output from main C-\\- pipeline stages. In case of + ``.cmm`` compilation this also dumps the result of + file parsing. Not included are passes run by + the chosen backend. Currently only the NCG backends runs + additional passes ( :ghc-flag:`-ddump-opt-cmm` ). + + Cmm dumps don't include unreachable blocks since we print + blocks in reverse post-order. + +.. ghc-flag:: -ddump-cmm-from-stg + :shortdesc: Dump STG-to-C-\\- output + :type: dynamic + + Dump the result of STG-to-C-\\- conversion + +.. ghc-flag:: -ddump-cmm-raw + :shortdesc: Dump raw C-\\- + :type: dynamic + + Dump the “raw” C-\\-. + +.. ghc-flag:: -ddump-cmm-cfg + :shortdesc: Dump the results of the C-\\- control flow optimisation pass. + :type: dynamic + + Dump the results of the C-\\- control flow optimisation pass. + +.. ghc-flag:: -ddump-cmm-cbe + :shortdesc: Dump the results of common block elimination + :type: dynamic + + Dump the results of the C-\\- Common Block Elimination (CBE) pass. + +.. ghc-flag:: -ddump-cmm-switch + :shortdesc: Dump the results of switch lowering passes + :type: dynamic + + Dump the results of the C-\\- switch lowering pass. + +.. ghc-flag:: -ddump-cmm-proc + :shortdesc: Dump the results of proc-point analysis + :type: dynamic + + Dump the results of the C-\\- proc-point analysis pass. + +.. ghc-flag:: -ddump-cmm-sp + :shortdesc: Dump the results of the C-\\- stack layout pass. + :type: dynamic + + Dump the results of the C-\\- stack layout pass. + +.. ghc-flag:: -ddump-cmm-sink + :shortdesc: Dump the results of the C-\\- sinking pass. + :type: dynamic + + Dump the results of the C-\\- sinking pass. + +.. ghc-flag:: -ddump-cmm-caf + :shortdesc: Dump the results of the C-\\- CAF analysis pass. + :type: dynamic + + Dump the results of the C-\\- CAF analysis pass. + +.. ghc-flag:: -ddump-cmm-procmap + :shortdesc: Dump the results of the C-\\- proc-point map pass. + :type: dynamic + + Dump the results of the C-\\- proc-point map pass. + +.. ghc-flag:: -ddump-cmm-split + :shortdesc: Dump the results of the C-\\- proc-point splitting pass. + :type: dynamic + + Dump the results of the C-\\- proc-point splitting pass. + +.. ghc-flag:: -ddump-cmm-info + :shortdesc: Dump the results of the C-\\- info table augmentation pass. + :type: dynamic + + Dump the results of the C-\\- info table augmentation pass. + +.. ghc-flag:: -ddump-cmm-cps + :shortdesc: Dump the results of the CPS pass + :type: dynamic + + Dump the results of the CPS pass. + +.. ghc-flag:: -ddump-cmm + :shortdesc: Dump the final C-\\- output + :type: dynamic + + Dump the result of the C-\\- pipeline processing + + + +LLVM code generator +~~~~~~~~~~~~~~~~~~~~~~ + +.. ghc-flag:: -ddump-llvm + :shortdesc: Dump LLVM intermediate code. + :type: dynamic + + :implies: :ghc-flag:`-fllvm` + + LLVM code from the :ref:`LLVM code generator <llvm-code-gen>` + +Native code generator +~~~~~~~~~~~~~~~~~~~~~ + +These flags dump various stages of the :ref:`native code generator's +<native-code-gen>` pipeline, which starts with C-\\- and produces native +assembler. + +.. ghc-flag:: -ddump-opt-cmm + :shortdesc: Dump the results of C-\\- to C-\\- optimising passes + :type: dynamic + + Dump the results of C-\\- to C-\\- optimising passes performed by the NCG. + +.. ghc-flag:: -ddump-asm-native + :shortdesc: Dump initial assembly + :type: dynamic + + Dump the initial assembler output produced from C-\\-. + +.. ghc-flag:: -ddump-asm-liveness + :shortdesc: Dump assembly augmented with register liveness + :type: dynamic + + Dump the result of the register liveness pass. + +.. ghc-flag:: -ddump-asm-regalloc + :shortdesc: Dump the result of register allocation + :type: dynamic + + Dump the result of the register allocation pass. + +.. ghc-flag:: -ddump-asm-regalloc-stages + :shortdesc: Dump the build/spill stages of the :ghc-flag:`-fregs-graph` + register allocator. + :type: dynamic + + Dump the build/spill stages of the :ghc-flag:`-fregs-graph` register + allocator. + +.. ghc-flag:: -ddump-asm-stats + :shortdesc: Dump statistics from the register allocator. + :type: dynamic + + Dump statistics from the register allocator. + +.. ghc-flag:: -ddump-asm-expanded + :shortdesc: Dump the result of the synthetic instruction expansion pass. + :type: dynamic + + Dump the result of the synthetic instruction expansion pass. + +.. ghc-flag:: -ddump-asm + :shortdesc: Dump final assembly + :type: dynamic + + Dump the final assembly produced by the native code generator. + + +Miscellaneous backend dumps +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +These flags dump various bits of information from other backends. + +.. ghc-flag:: -ddump-bcos + :shortdesc: Dump interpreter byte code + :type: dynamic + + Dump byte-code objects (BCOs) produced for the GHC's byte-code interpreter. + +.. ghc-flag:: -ddump-rtti + :shortdesc: Trace runtime type inference + :type: dynamic + + Trace runtime type inference done by various interpreter commands. + +.. ghc-flag:: -ddump-foreign + :shortdesc: Dump ``foreign export`` stubs + :type: dynamic + + Dump foreign export stubs. - Debugging output is in one of several "styles." Take the printing of - types, for example. In the "user" style (the default), the - compiler's internal ideas about types are presented in Haskell - source-level syntax, insofar as possible. In the "debug" style - (which is the default for debugging output), the types are printed - in with explicit foralls, and variables have their unique-id - attached (so you can check for things that look the same but - aren't). This flag makes debugging output appear in the more verbose - debug style. .. _formatting dumps: @@ -277,23 +580,46 @@ Formatting dumps single: formatting dumps .. ghc-flag:: -dppr-user-length + :shortdesc: Set the depth for printing expressions in error msgs + :type: dynamic In error messages, expressions are printed to a certain "depth", with subexpressions beyond the depth replaced by ellipses. This flag sets the depth. Its default value is 5. .. ghc-flag:: -dppr-cols=⟨n⟩ + :shortdesc: Set the width of debugging output. For example ``-dppr-cols200`` + :type: dynamic Set the width of debugging output. Use this if your code is wrapping too much. For example: ``-dppr-cols=200``. .. ghc-flag:: -dppr-case-as-let + :shortdesc: Print single alternative case expressions as strict lets. + :type: dynamic Print single alternative case expressions as though they were strict let expressions. This is helpful when your code does a lot of unboxing. +.. ghc-flag:: -dhex-word-literals + :shortdesc: Print values of type `Word#` in hexadecimal. + :type: dynamic + + Print values of type `Word#` and `Word64#` (but not values of + type `Int#` and `Int64#`) in hexadecimal instead of decimal. + The hexadecimal is zero-padded to make the length of the + representation a power of two. For example: `0x0A0A##`, + `0x000FFFFF##`, `0xC##`. This flag may be helpful when you + are producing a bit pattern that to expect to work correctly on a 32-bit + or a 64-bit architecture. Dumping hexadecimal literals after + optimizations and constant folding makes it easier to confirm + that the generated bit pattern is correct. + .. ghc-flag:: -dno-debug-output + :shortdesc: Suppress unsolicited debugging output + :type: dynamic + :reverse: -ddebug-output Suppress any unsolicited debugging output. When GHC has been built with the ``DEBUG`` option it occasionally emits debug output of @@ -314,16 +640,24 @@ are doing, not all of it will be useful. Use these flags to suppress the parts that you are not interested in. .. ghc-flag:: -dsuppress-all + :shortdesc: In dumps, suppress everything (except for uniques) that is + suppressible. + :type: dynamic Suppress everything that can be suppressed, except for unique ids as this often makes the printout ambiguous. If you just want to see the overall structure of the code, then start here. .. ghc-flag:: -dsuppress-ticks + :shortdesc: Suppress "ticks" in the pretty-printer output. + :type: dynamic Suppress "ticks" in the pretty-printer output. .. ghc-flag:: -dsuppress-uniques + :shortdesc: Suppress the printing of uniques in debug output (easier to use + ``diff``) + :type: dynamic Suppress the printing of uniques. This may make the printout ambiguous (e.g. unclear where an occurrence of 'x' is bound), but it @@ -333,6 +667,9 @@ parts that you are not interested in. :ghc-flag:`-dsuppress-uniques` .. ghc-flag:: -dsuppress-idinfo + :shortdesc: Suppress extended information about identifiers where they + are bound + :type: dynamic Suppress extended information about identifiers where they are bound. This includes strictness information and inliner templates. @@ -340,27 +677,59 @@ parts that you are not interested in. the lack of inliner templates .. ghc-flag:: -dsuppress-unfoldings + :shortdesc: Suppress the printing of the stable unfolding of a variable at + its binding site + :type: dynamic Suppress the printing of the stable unfolding of a variable at its binding site. .. ghc-flag:: -dsuppress-module-prefixes + :shortdesc: Suppress the printing of module qualification prefixes + :type: dynamic Suppress the printing of module qualification prefixes. This is the ``Data.List`` in ``Data.List.length``. +.. ghc-flag:: -dsuppress-timestamps + :shortdesc: Suppress timestamps in dumps + :type: dynamic + + Suppress the printing of timestamps. + This makes it easier to diff dumps. + .. ghc-flag:: -dsuppress-type-signatures + :shortdesc: Suppress type signatures + :type: dynamic Suppress the printing of type signatures. .. ghc-flag:: -dsuppress-type-applications + :shortdesc: Suppress type applications + :type: dynamic Suppress the printing of type applications. .. ghc-flag:: -dsuppress-coercions + :shortdesc: Suppress the printing of coercions in Core dumps to make them + shorter + :type: dynamic Suppress the printing of type coercions. +.. ghc-flag:: -dsuppress-var-kinds + :shortdesc: Suppress the printing of variable kinds + :type: dynamic + + Suppress the printing of variable kinds + +.. ghc-flag:: -dsuppress-stg-free-vars + :shortdesc: Suppress the printing of closure free variable lists in STG output + :type: dynamic + + Suppress the printing of closure free variable lists in STG output + + .. _checking-consistency: Checking for consistency @@ -371,25 +740,54 @@ Checking for consistency single: lint .. ghc-flag:: -dcore-lint + :shortdesc: Turn on internal sanity checking + :type: dynamic Turn on heavyweight intra-pass sanity-checking within GHC, at Core level. (It checks GHC's sanity, not yours.) .. ghc-flag:: -dstg-lint + :shortdesc: STG pass sanity checking + :type: dynamic - Ditto for STG level. (note: currently doesn't work). + Ditto for STG level. .. ghc-flag:: -dcmm-lint + :shortdesc: C-\\- pass sanity checking + :type: dynamic - Ditto for C-- level. + Ditto for C-\\- level. .. ghc-flag:: -fllvm-fill-undef-with-garbage + :shortdesc: Intruct LLVM to fill dead STG registers with garbage + :type: dynamic Instructs the LLVM code generator to fill dead STG registers with garbage instead of ``undef`` in calls. This makes it easier to catch subtle code generator and runtime system bugs (e.g. see :ghc-ticket:`11487`). +.. ghc-flag:: -falignment-sanitisation + :shortdesc: Compile with alignment checks for all info table dereferences. + :type: dynamic + + Compile with alignment checks for all info table dereferences. This can be + useful when finding pointer tagging issues. + +.. ghc-flag:: -fproc-alignment + :shortdesc: Align functions at given boundary. + :type: dynamic + + Align functions to multiples of the given value. Only valid values are powers + of two. + + ``-fproc-alignment=64`` can be used to limit alignment impact on performance + as each function will start at a cache line. + However forcing larger alignments in general reduces performance. + .. ghc-flag:: -fcatch-bottoms + :shortdesc: Insert ``error`` expressions after bottoming expressions; useful + when debugging the compiler. + :type: dynamic Instructs the simplifier to emit ``error`` expressions in the continuation of empty case analyses (which should bottom and consequently not return). @@ -405,10 +803,14 @@ Checking for determinism single: deterministic builds .. ghc-flag:: -dinitial-unique=⟨s⟩ + :shortdesc: Start ``UniqSupply`` allocation from ⟨s⟩. + :type: dynamic Start ``UniqSupply`` allocation from ⟨s⟩. .. ghc-flag:: -dunique-increment=⟨i⟩ + :shortdesc: Set the increment for the generated ``Unique``'s to ⟨i⟩. + :type: dynamic Set the increment for the generated ``Unique``'s to ⟨i⟩. |