diff options
Diffstat (limited to 'src/cmd/compile/internal/noder/unified.go')
| -rw-r--r-- | src/cmd/compile/internal/noder/unified.go | 50 |
1 files changed, 45 insertions, 5 deletions
diff --git a/src/cmd/compile/internal/noder/unified.go b/src/cmd/compile/internal/noder/unified.go index 96c0916493..7a1bb88537 100644 --- a/src/cmd/compile/internal/noder/unified.go +++ b/src/cmd/compile/internal/noder/unified.go @@ -28,9 +28,48 @@ import ( // later. var localPkgReader *pkgReader -// useUnifiedIR reports whether the unified IR frontend should be -// used; and if so, uses it to construct the local package's IR. -func useUnifiedIR(noders []*noder) { +// unified construct the local package's IR from syntax's AST. +// +// The pipeline contains 2 steps: +// +// (1) Generate package export data "stub". +// +// (2) Generate package IR from package export data. +// +// The package data "stub" at step (1) contains everything from the local package, +// but nothing that have been imported. When we're actually writing out export data +// to the output files (see writeNewExport function), we run the "linker", which does +// a few things: +// +// + Updates compiler extensions data (e.g., inlining cost, escape analysis results). +// +// + Handles re-exporting any transitive dependencies. +// +// + Prunes out any unnecessary details (e.g., non-inlineable functions, because any +// downstream importers only care about inlinable functions). +// +// The source files are typechecked twice, once before writing export data +// using types2 checker, once after read export data using gc/typecheck. +// This duplication of work will go away once we always use types2 checker, +// we can remove the gc/typecheck pass. The reason it is still here: +// +// + It reduces engineering costs in maintaining a fork of typecheck +// (e.g., no need to backport fixes like CL 327651). +// +// + It makes it easier to pass toolstash -cmp. +// +// + Historically, we would always re-run the typechecker after import, even though +// we know the imported data is valid. It's not ideal, but also not causing any +// problem either. +// +// + There's still transformation that being done during gc/typecheck, like rewriting +// multi-valued function call, or transform ir.OINDEX -> ir.OINDEXMAP. +// +// Using syntax+types2 tree, which already has a complete representation of generics, +// the unified IR has the full typed AST for doing introspection during step (1). +// In other words, we have all necessary information to build the generic IR form +// (see writer.captureVars for an example). +func unified(noders []*noder) { inline.NewInline = InlineCall if !quirksMode() { @@ -111,8 +150,9 @@ func useUnifiedIR(noders []*noder) { base.ExitIfErrors() // just in case } -// writePkgStub type checks the given parsed source files and then -// returns +// writePkgStub type checks the given parsed source files, +// writes an export data package stub representing them, +// and returns the result. func writePkgStub(noders []*noder) string { m, pkg, info := checkFiles(noders) |