[GOLD] PowerPC notoc eh_frame

When generating notoc call and branch stubs without the benefit of
pc-relative insns, the stubs need to use LR to access the run time PC.
All LR changes must be described in .eh_frame if we're to support
unwinding through asynchronous exceptions.  That's what this patch
does.

The patch has gone through way too many iterations.  At first I
attempted to add multiple FDEs, one for each stub.  That ran into
difficulties with do_plt_fde_location which is only capable of setting
the address of a single FDE per Output_data section, and with removing
any FDEs added on a previous do_relax pass.  Removing FDEs (git commit
be897fb774) went overboard in matching the FDE contents.  That means
either stashing the contents created for add_eh_frame_for_plt to use
when calling remove_eh_frame_for_plt, or recreating contents on the
fly (*) just to remove FDEs.  In fact, FDE content matching is quite
unnecesary.  FDEs added by a previous do_relax pass are those with
u_.from_linker.post_map set.  So they can easily be recognised just by
looking at that flag.  This patch keeps that part of the multiple FDE
changes.

In the end I went for just one FDE per stub group to describe the call
stubs.  That's reasonably efficient for the common case of only
needing to describe the __tls_get_addr_opt call stub.  We don't expect
to be making many calls using notoc stubs without pc-relative insns.

*) Which has it's own set of problems.  The contents must be recreated
using the old stub layout, but .eh_frame size can affect stub
requirements so you need to temporarily keep the old .eh_frame size
when creating new stubs, then reset .eh_frame size before adding new
FDEs.

	* ehframe.cc (Fde::operator==): Delete.
	(Cie::remove_fde): Delete.
	(Eh_frame::remove_ehframe_for_plt): Delete fde_data and fde_length
	parameters.  Remove all post-map plt FDEs.
	* ehframe.h (Fde:post_map): Make const, add variant to compare plt.
	(Fde::operator==): Delete.
	(Cie::remove_fde): Implement here.
	(Cie::last_fde): New accessor.
	(Eh_frame::remove_ehframe_for_plt): Update prototype.
	* layout.cc (Layout::remove_eh_frame_for_plt): Delete fde_data and
	fde_length parameters.
	* layout.h (Layout::remove_eh_frame_for_plt): Update prototype.
	* powerpc.cc (Stub_table::tls_get_addr_opt_bctrl_): Delete.
	(Stub_table::plt_fde_len_, plt_fde_, init_plt_fde): Delete.
	(Stub_table::add_plt_call_entry): Don't set tls_get_addr_opt_bctrl_.
	(eh_advance): New function.
	(stub_sort): New function.
	(Stub_table::add_eh_frame): Emit eh_frame for notoc plt calls and
	branches as well as __tls_get_addr_opt plt call stub.
	(Stub_table::remove_eh_frame): Update to suit.

1 files changed, 14 insertions, 33 deletions

diff --git a/gold/ehframe.cc b/gold/ehframe.cc
index df056d3d362..51490e0e908 100644
--- a/gold/ehframe.cc
+++ b/gold/ehframe.cc
@@ -325,21 +325,6 @@ Eh_frame_hdr::get_fde_addresses(Output_file* of,
 
 // Class Fde.
 
-bool
-Fde::operator==(const Fde& that) const
-{
-  if (this->object_ != that.object_
-      || this->contents_ != that.contents_)
-    return false;
-  if (this->object_ == NULL)
-    return (this->u_.from_linker.plt == that.u_.from_linker.plt
-	    && this->u_.from_linker.post_map == that.u_.from_linker.post_map);
-  else
-    return (this->u_.from_object.shndx == that.u_.from_object.shndx
-	    && (this->u_.from_object.input_offset
-		== that.u_.from_object.input_offset));
-}
-
 // Write the FDE to OVIEW starting at OFFSET.  CIE_OFFSET is the
 // offset of the CIE in OVIEW.  OUTPUT_OFFSET is the offset of the
 // Eh_frame section within the output section.  FDE_ENCODING is the
@@ -458,15 +443,6 @@ Cie::set_output_offset(section_offset_type output_offset,
   return output_offset + length;
 }
 
-// Remove FDE.  Only the last FDE using this CIE may be removed.
-
-void
-Cie::remove_fde(const Fde* fde)
-{
-  gold_assert(*fde == *this->fdes_.back());
-  this->fdes_.pop_back();
-}
-
 // Write the CIE to OVIEW starting at OFFSET.  OUTPUT_OFFSET is the
 // offset of the Eh_frame section within the output section.  Round up
 // the bytes to ADDRALIGN.  ADDRESS is the virtual address of OVIEW.
@@ -1167,26 +1143,31 @@ Eh_frame::add_ehframe_for_plt(Output_data* plt, const unsigned char* cie_data,
     this->final_data_size_ += align_address(fde_length + 8, this->addralign());
 }
 
-// Remove unwind information for a PLT.  Only the last FDE added may be removed.
+// Remove all post-map unwind information for a PLT.
 
 void
 Eh_frame::remove_ehframe_for_plt(Output_data* plt,
 				 const unsigned char* cie_data,
-				 size_t cie_length,
-				 const unsigned char* fde_data,
-				 size_t fde_length)
+				 size_t cie_length)
 {
+  if (!this->mappings_are_done_)
+    return;
+
   Cie cie(NULL, 0, 0, elfcpp::DW_EH_PE_pcrel | elfcpp::DW_EH_PE_sdata4, "",
 	  cie_data, cie_length);
   Cie_offsets::iterator find_cie = this->cie_offsets_.find(&cie);
   gold_assert (find_cie != this->cie_offsets_.end());
   Cie* pcie = *find_cie;
 
-  Fde* fde = new Fde(plt, fde_data, fde_length, this->mappings_are_done_);
-  pcie->remove_fde(fde);
-
-  if (this->mappings_are_done_)
-    this->final_data_size_ -= align_address(fde_length + 8, this->addralign());
+  while (pcie->fde_count() != 0)
+    {
+      const Fde* fde = pcie->last_fde();
+      if (!fde->post_map(plt))
+	break;
+      size_t length = fde->length();
+      this->final_data_size_ -= align_address(length + 8, this->addralign());
+      pcie->remove_fde();
+    }
 }
 
 // Return the number of FDEs.