9e7548ab31
This changes the license information in many of the flang source files. - Renamed LICENSE to LICENSE.txt. - NVIDIA Copyright lines have been removed. - Initial lines for files follow the LLVM coding convention (file name on the first line; Emacs mode information on the first line). - License references have been replaced with the abridged LLVM text. - License information was removed from the test files. - No file header was placed on test files (these weren't in most LLVM test files). - License information was added to documentation files where it was missing. We did not add brief file summaries to the initial line. See http://llvm.org/docs/DeveloperPolicy.html#new-llvm-project-license-framework for a description of the new license. See http://llvm.org/docs/CodingStandards.html#file-headers for a description of the new LLVM standard file header. Original-commit: flang-compiler/f18@add6cde724 Reviewed-on: https://github.com/flang-compiler/f18/pull/887
104 lines
3.4 KiB
Markdown
104 lines
3.4 KiB
Markdown
<!--===- documentation/Overview.md
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Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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See https://llvm.org/LICENSE.txt for license information.
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SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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-->
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# Overview of Compiler Phases
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Each phase produces either correct output or fatal errors.
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## Prescan and Preprocess
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See: [Preprocessing.md](Preprocessing.md).
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**Input:** Fortran source and header files, command line macro definitions,
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set of enabled compiler directives (to be treated as directives rather than
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comments).
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**Output:**
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- A "cooked" character stream: the entire program as a contiguous stream of
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normalized Fortran source.
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Extraneous whitespace and comments are removed (except comments that are
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compiler directives that are not disabled) and case is normalized.
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- Provenance information mapping each character back to the source it came from.
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This is used in subsequent phases to issue errors messages that refer to source locations.
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**Entry point:** `parser::Parsing::Prescan`
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**Command:** `f18 -E src.f90` dumps the cooked character stream
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## Parse
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**Input:** Cooked character stream.
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**Output:** A parse tree representing a syntactically correct program,
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rooted at a `parser::Program`.
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See: [Parsing.md](Parsing.md) and [ParserCombinators.md](ParserCombinators.md).
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**Entry point:** `parser::Parsing::Parse`
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**Command:**
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- `f18 -fdebug-dump-parse-tree -fparse-only src.f90` dumps the parse tree
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- `f18 -funparse src.f90` converts the parse tree to normalized Fortran
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## Validate Labels and Canonicalize Do Statements
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**Input:** Parse tree.
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**Output:** The parse tree with label constraints and construct names checked,
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and each `LabelDoStmt` converted to a `NonLabelDoStmt`.
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See: [LabelResolution.md](LabelResolution.md).
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**Entry points:** `semantics::ValidateLabels`, `parser::CanonicalizeDo`
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## Resolve Names
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**Input:** Parse tree (without `LabelDoStmt`) and `.mod` files from compilation
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of USEd modules.
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**Output:**
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- Tree of scopes populated with symbols and types
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- Parse tree with some refinements:
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- each `parser::Name::symbol` field points to one of the symbols
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- each `parser::TypeSpec::declTypeSpec` field points to one of the types
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- array element references that were parsed as function references or
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statement functions are corrected
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**Entry points:** `semantics::ResolveNames`, `semantics::RewriteParseTree`
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**Command:** `f18 -fdebug-dump-symbols -fparse-only src.f90` dumps the
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tree of scopes and symbols in each scope
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## Check DO CONCURRENT Constraints
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**Input:** Parse tree with names resolved.
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**Output:** Parse tree with semantically correct DO CONCURRENT loops.
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## Write Module Files
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**Input:** Parse tree with names resolved.
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**Output:** For each module and submodule, a `.mod` file containing a minimal
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Fortran representation suitable for compiling program units that depend on it.
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See [ModFiles.md](ModFiles.md).
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## Analyze Expressions and Assignments
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**Input:** Parse tree with names resolved.
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**Output:** Parse tree with `parser::Expr::typedExpr` filled in and semantic
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checks performed on all expressions and assignment statements.
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**Entry points**: `semantics::AnalyzeExpressions`, `semantics::AnalyzeAssignments`
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## Produce the Intermediate Representation
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**Input:** Parse tree with names and labels resolved.
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**Output:** An intermediate representation of the executable program.
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See [FortranIR.md](FortranIR.md).
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