Go patch committed: Support bootstrapping Go 1.21

Go patch committed: Support bootstrapping Go 1.21

[Ian Lance Taylor]

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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 patch 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 Go
frontend recognizes and intrinsifies those functions as well.
However, the Go frontend 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
patch arranges to not generate function descriptors for these
functions.

This helps address https://go.dev/issue/60913.

Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
to mainline and GCC 12 and 13 branches.

Ian

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2ad5553091d8afbc21bbd3a29a419df359e7aacc
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index a028350ba8e..ff07b1a1fa6 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-195060166e6045408a2cb95e6aa88c6f0b98f20b
+68a756b6aadc901534cfddddad2b1e73fae9e34f
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/gcc/go/gofrontend/expressions.cc b/gcc/go/gofrontend/expressions.cc
index 2112de6abfc..d276bd811cc 100644
--- a/gcc/go/gofrontend/expressions.cc
+++ b/gcc/go/gofrontend/expressions.cc
@@ -12272,7 +12272,8 @@ 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 9197eef3e38..980db1ea07e 100644
--- a/gcc/go/gofrontend/gogo.cc
+++ b/gcc/go/gofrontend/gogo.cc
@@ -3296,6 +3296,9 @@ class Create_function_descriptors : public Traverse
   int
   expression(Expression**);
 
+  static bool
+  skip_descriptor(Gogo* gogo, const Named_object*);
+
  private:
   Gogo* gogo_;
 };
@@ -3306,6 +3309,9 @@ 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()
@@ -3393,6 +3399,28 @@ 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.
@@ -3414,7 +3442,8 @@ 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 920f8cc7071..c95dc2106cd 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/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