[gcc/devel/rust/master] rust: Add -frust-compile-until option

[Thomas Schwinge <tschwinge@gcc.gnu.org>]

https://gcc.gnu.org/g:138a6260124740208b8f3aff2e38617f43b05fe8

commit 138a6260124740208b8f3aff2e38617f43b05fe8
Author: Arthur Cohen <arthur.cohen@embecosm.com>
Date:   Wed Aug 31 13:53:28 2022 +0200

    rust: Add -frust-compile-until option
    
    This option helps ensure that we do not introduce regressions on various
    parts of the compilation pipeline. For example, a testcase (or testsuite
    from the `testing` project) might pass attribute checking, expansion and
    lowering, but fail during typechecking. Should a change suddenly make
    that testcase fail expansion, we would not be able to notice it. By
    generating tests that run up until expansion, typechecking, compilation
    and so forth we ensure that no regressions are added accidentally to
    already failing tests/testsuites.

Diff:
---
 gcc/rust/lang.opt                                 | 42 +++++++++++++++++++++++
 gcc/rust/rust-session-manager.cc                  | 36 +++++++++++++++++--
 gcc/rust/rust-session-manager.h                   | 25 +++++++++++++-
 gcc/testsuite/rust/compile/frust-compile-until.rs |  7 ++++
 4 files changed, 107 insertions(+), 3 deletions(-)

diff --git a/gcc/rust/lang.opt b/gcc/rust/lang.opt
index 1f6855ede1d..bb3b9983862 100644
--- a/gcc/rust/lang.opt
+++ b/gcc/rust/lang.opt
@@ -113,6 +113,48 @@ Rust Joined RejectNegative
 
 o
 Rust Joined Separate
+
+frust-compile-until=
+Rust Joined RejectNegative Enum(frust_compile_until) Var(flag_rust_compile_until)
+-frust-compile-until=[ast|attributecheck|expansion|nameresolution|lowering|typecheck|privacy|unsafety|const|copimlation|end]             When to stop in the pipeline when compiling Rust code
+
+Enum
+Name(frust_compile_until) Type(int) UnknownError(unknown rust compile-until %qs)
+
+EnumValue
+Enum(frust_compile_until) String(ast) Value(0)
+
+EnumValue
+Enum(frust_compile_until) String(attributecheck) Value(1)
+
+EnumValue
+Enum(frust_compile_until) String(expansion) Value(2)
+
+EnumValue
+Enum(frust_compile_until) String(nameresolution) Value(3)
+
+EnumValue
+Enum(frust_compile_until) String(lowering) Value(4)
+
+EnumValue
+Enum(frust_compile_until) String(typecheck) Value(5)
+
+EnumValue
+Enum(frust_compile_until) String(privacy) Value(6)
+
+EnumValue
+Enum(frust_compile_until) String(unsafety) Value(7)
+
+EnumValue
+Enum(frust_compile_until) String(const) Value(8)
+
+EnumValue
+Enum(frust_compile_until) String(compilation) Value(9)
+
+EnumValue
+Enum(frust_compile_until) String(end) Value(10)
+
+
 ; Documented in common.opt
 
 ; This comment is to ensure we retain the blank line above.
diff --git a/gcc/rust/rust-session-manager.cc b/gcc/rust/rust-session-manager.cc
index fc66b692c95..a6291a3cab8 100644
--- a/gcc/rust/rust-session-manager.cc
+++ b/gcc/rust/rust-session-manager.cc
@@ -223,7 +223,9 @@ Session::handle_option (
     case OPT_frust_edition_:
       options.set_edition (flag_rust_edition);
       break;
-
+    case OPT_frust_compile_until_:
+      options.set_compile_step (flag_rust_compile_until);
+      break;
     case OPT_frust_metadata_output_:
       options.set_metadata_output (arg);
       break;
@@ -425,6 +427,8 @@ Session::compile_crate (const char *filename)
       return;
     }
 
+  auto last_step = options.get_compile_until ();
+
   // parse file here
   /* create lexer and parser - these are file-specific and so aren't instance
    * variables */
@@ -481,7 +485,7 @@ Session::compile_crate (const char *filename)
 
   // If -fsyntax-only was passed, we can just skip the remaining passes.
   // Parsing errors are already emitted in `parse_crate()`
-  if (flag_syntax_only)
+  if (flag_syntax_only || last_step == CompileOptions::CompileStep::Ast)
     return;
 
   // register plugins pipeline stage
@@ -500,8 +504,14 @@ Session::compile_crate (const char *filename)
       // TODO: what do I dump here? injected crate names?
     }
 
+  if (last_step == CompileOptions::CompileStep::AttributeCheck)
+    return;
+
   Analysis::AttributeChecker ().go (parsed_crate);
 
+  if (last_step == CompileOptions::CompileStep::Expansion)
+    return;
+
   // expansion pipeline stage
   expansion (parsed_crate);
   rust_debug ("\033[0;31mSUCCESSFULLY FINISHED EXPANSION \033[0m");
@@ -514,6 +524,9 @@ Session::compile_crate (const char *filename)
       rust_debug ("END POST-EXPANSION AST DUMP");
     }
 
+  if (last_step == CompileOptions::CompileStep::NameResolution)
+    return;
+
   // resolution pipeline stage
   Resolver::NameResolution::Resolve (parsed_crate);
   if (options.dump_option_enabled (CompileOptions::RESOLUTION_DUMP))
@@ -524,6 +537,9 @@ Session::compile_crate (const char *filename)
   if (saw_errors ())
     return;
 
+  if (last_step == CompileOptions::CompileStep::Lowering)
+    return;
+
   // lower AST to HIR
   std::unique_ptr<HIR::Crate> lowered
     = HIR::ASTLowering::Resolve (parsed_crate);
@@ -541,6 +557,9 @@ Session::compile_crate (const char *filename)
       dump_hir_pretty (hir);
     }
 
+  if (last_step == CompileOptions::CompileStep::TypeCheck)
+    return;
+
   // type resolve
   Resolver::TypeResolution::Resolve (hir);
   if (options.dump_option_enabled (CompileOptions::TYPE_RESOLUTION_DUMP))
@@ -551,17 +570,30 @@ Session::compile_crate (const char *filename)
   if (saw_errors ())
     return;
 
+  if (last_step == CompileOptions::CompileStep::Privacy)
+    return;
+
   // Various HIR error passes. The privacy pass happens before the unsafe checks
   Privacy::Resolver::resolve (hir);
   if (saw_errors ())
     return;
 
+  if (last_step == CompileOptions::CompileStep::Unsafety)
+    return;
+
   HIR::UnsafeChecker ().go (hir);
+
+  if (last_step == CompileOptions::CompileStep::Const)
+    return;
+
   HIR::ConstChecker ().go (hir);
 
   if (saw_errors ())
     return;
 
+  if (last_step == CompileOptions::CompileStep::Compilation)
+    return;
+
   // do compile to gcc generic
   Compile::Context ctx (backend);
   Compile::CompileCrate::Compile (hir, &ctx);
diff --git a/gcc/rust/rust-session-manager.h b/gcc/rust/rust-session-manager.h
index b3724c540c3..6ecd51315c5 100644
--- a/gcc/rust/rust-session-manager.h
+++ b/gcc/rust/rust-session-manager.h
@@ -199,6 +199,22 @@ struct CompileOptions
   } edition
     = Edition::E2015;
 
+  enum class CompileStep
+  {
+    Ast,
+    AttributeCheck,
+    Expansion,
+    NameResolution,
+    Lowering,
+    TypeCheck,
+    Privacy,
+    Unsafety,
+    Const,
+    Compilation,
+    End,
+  } compile_until
+    = CompileStep::End;
+
   bool dump_option_enabled (DumpOption option) const
   {
     return dump_options.find (option) != dump_options.end ();
@@ -239,7 +255,14 @@ struct CompileOptions
     edition = static_cast<Edition> (raw_edition);
   }
 
-  const Edition &get_edition () { return edition; }
+  const Edition &get_edition () const { return edition; }
+
+  void set_compile_step (int raw_step)
+  {
+    compile_until = static_cast<CompileStep> (raw_step);
+  }
+
+  const CompileStep &get_compile_until () const { return compile_until; }
 
   void set_metadata_output (const std::string &path)
   {
diff --git a/gcc/testsuite/rust/compile/frust-compile-until.rs b/gcc/testsuite/rust/compile/frust-compile-until.rs
new file mode 100644
index 00000000000..7bb3932ef60
--- /dev/null
+++ b/gcc/testsuite/rust/compile/frust-compile-until.rs
@@ -0,0 +1,7 @@
+// { dg-additional-options "-frust-compile-until=unsafety" }
+
+unsafe fn foo() {}
+
+fn main() {
+    foo()
+}