[gcc r12-9725] compiler, libgo: support bootstrapping gc compiler

[gcc r12-9725] compiler, libgo: support bootstrapping gc compiler

[Ian Lance Taylor]

https://gcc.gnu.org/g:f4d011b4aa0fc7a9e3df0dada2fd3e1e95e32a6c

commit r12-9725-gf4d011b4aa0fc7a9e3df0dada2fd3e1e95e32a6c
Author: Ian Lance Taylor <iant@golang.org>
Date:   Fri Jun 23 16:16:06 2023 -0700

    compiler, libgo: support bootstrapping gc compiler
    
    In the Go 1.21 release the package internal/profile imports
    internal/lazyregexp.  That works when bootstrapping with Go 1.17,
    because that compiler has internal/lazyregep and permits importing it.
    We also have internal/lazyregexp in libgo, but since it is not installed
    it is not available for importing.  This CL adds internal/lazyregexp
    to the list of internal packages that are installed for bootstrapping.
    
    The Go 1.21, and earlier, releases have a couple of functions in
    the internal/abi package that are always fully intrinsified.
    The gofrontend recognizes and intrinsifies those functions as well.
    However, the gofrontend was also building function descriptors
    for references to the functions without calling them, which
    failed because there was nothing to refer to.  That is OK for the
    gc compiler, which guarantees that the functions are only called,
    not referenced.  This CL arranges to not generate function descriptors
    for these functions.
    
    For golang/go#60913
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/504798

Diff:
---
 gcc/go/gofrontend/expressions.cc |  3 ++-
 gcc/go/gofrontend/gogo.cc        | 31 ++++++++++++++++++++++++++++++-
 libgo/Makefile.am                |  1 +
 libgo/Makefile.in                |  1 +
 libgo/go/internal/abi/abi.go     | 10 ++--------
 5 files changed, 36 insertions(+), 10 deletions(-)

diff --git a/gcc/go/gofrontend/expressions.cc b/gcc/go/gofrontend/expressions.cc
index 1b3b3bf135e..88b4ceacc07 100644
--- a/gcc/go/gofrontend/expressions.cc
+++ b/gcc/go/gofrontend/expressions.cc
@@ -12325,7 +12325,8 @@ Call_expression::intrinsify(Gogo* gogo,
           return Runtime::make_call(code, loc, 3, a1, a2, a3);
         }
     }
-  else if (package == "internal/abi")
+  else if (package == "internal/abi"
+	   || package == "bootstrap/internal/abi") // for bootstrapping gc
     {
       if (is_method)
 	return NULL;
diff --git a/gcc/go/gofrontend/gogo.cc b/gcc/go/gofrontend/gogo.cc
index d35c6baf582..cca03dcdc35 100644
--- a/gcc/go/gofrontend/gogo.cc
+++ b/gcc/go/gofrontend/gogo.cc
@@ -3331,6 +3331,9 @@ class Create_function_descriptors : public Traverse
   int
   expression(Expression**);
 
+  static bool
+  skip_descriptor(Gogo* gogo, const Named_object*);
+
  private:
   Gogo* gogo_;
 };
@@ -3341,6 +3344,9 @@ class Create_function_descriptors : public Traverse
 int
 Create_function_descriptors::function(Named_object* no)
 {
+  if (Create_function_descriptors::skip_descriptor(this->gogo_, no))
+    return TRAVERSE_CONTINUE;
+
   if (no->is_function()
       && no->func_value()->enclosing() == NULL
       && !no->func_value()->is_method()
@@ -3428,6 +3434,28 @@ Create_function_descriptors::expression(Expression** pexpr)
   return TRAVERSE_CONTINUE;
 }
 
+// The gc compiler has some special cases that it always compiles as
+// intrinsics.  For those we don't want to generate a function
+// descriptor, as there will be no code for it to refer to.
+
+bool
+Create_function_descriptors::skip_descriptor(Gogo* gogo,
+					     const Named_object* no)
+{
+  const std::string& pkgpath(no->package() == NULL
+			     ? gogo->pkgpath()
+			     : no->package()->pkgpath());
+
+  // internal/abi is the standard library package,
+  // bootstrap/internal/abi is the name used when bootstrapping the gc
+  // compiler.
+
+  return ((pkgpath == "internal/abi"
+	   || pkgpath == "bootstrap/internal/abi")
+	  && (no->name() == "FuncPCABI0"
+	      || no->name() == "FuncPCABIInternal"));
+}
+
 // Create function descriptors as needed.  We need a function
 // descriptor for all exported functions and for all functions that
 // are referenced without being called.
@@ -3449,7 +3477,8 @@ Gogo::create_function_descriptors()
       if (no->is_function_declaration()
 	  && !no->func_declaration_value()->type()->is_method()
 	  && !Linemap::is_predeclared_location(no->location())
-	  && !Gogo::is_hidden_name(no->name()))
+	  && !Gogo::is_hidden_name(no->name())
+	  && !Create_function_descriptors::skip_descriptor(this, no))
 	fndecls.push_back(no);
     }
   for (std::vector<Named_object*>::const_iterator p = fndecls.begin();
diff --git a/libgo/Makefile.am b/libgo/Makefile.am
index b03e6553e90..c273d94d111 100644
--- a/libgo/Makefile.am
+++ b/libgo/Makefile.am
@@ -417,6 +417,7 @@ toolexeclibgounicode_DATA = \
 # Some internal packages are needed to bootstrap the gc toolchain.
 toolexeclibgointernaldir = $(toolexeclibgodir)/internal
 toolexeclibgointernal_DATA = \
+	internal/lazyregexp.gox \
 	internal/reflectlite.gox \
 	internal/unsafeheader.gox
 
diff --git a/libgo/Makefile.in b/libgo/Makefile.in
index 16ed62a82ed..04fdb60d497 100644
--- a/libgo/Makefile.in
+++ b/libgo/Makefile.in
@@ -885,6 +885,7 @@ toolexeclibgounicode_DATA = \
 # Some internal packages are needed to bootstrap the gc toolchain.
 toolexeclibgointernaldir = $(toolexeclibgodir)/internal
 toolexeclibgointernal_DATA = \
+	internal/lazyregexp.gox \
 	internal/reflectlite.gox \
 	internal/unsafeheader.gox
 
diff --git a/libgo/go/internal/abi/abi.go b/libgo/go/internal/abi/abi.go
index c4a108847ca..66251274d97 100644
--- a/libgo/go/internal/abi/abi.go
+++ b/libgo/go/internal/abi/abi.go
@@ -17,10 +17,7 @@ package abi
 // compile-time error.
 //
 // Implemented as a compile intrinsic.
-func FuncPCABI0(f any) uintptr {
-	// The compiler should remove all calls.
-	panic("FuncPCABI0")
-}
+func FuncPCABI0(f any) uintptr
 
 // FuncPCABIInternal returns the entry PC of the function f. If f is a
 // direct reference of a function, it must be defined as ABIInternal.
@@ -29,7 +26,4 @@ func FuncPCABI0(f any) uintptr {
 // the behavior is undefined.
 //
 // Implemented as a compile intrinsic.
-func FuncPCABIInternal(f any) uintptr {
-	// The compiler should remove all calls.
-	panic("FuncPCABIInternal")
-}
+func FuncPCABIInternal(f any) uintptr