Re: [patch][gold] Don't put rodata and text in the same segment.

[Rafael Espindola <espindola at google dot com>]

Looking a bit more in the code I was curious why the optimization of
trying to keep the data contiguous on disk but not in memory could not
be applied in more cases. I also noticed that was_readonly was never
being set back to false. Is it because the code knows how the segments
are ordered? That is wrong in the presence of large segments, no?

Anyway, I tried to apply the optimization unconditionally and I could
not find a case that fails. Would you mind reviewing the attached
patch first? If you do know a case that would fail let me know and I
will add a testcase for it instead.

2010-09-03  Rafael Espindola  <espindola@google.com>

       * layout.cc (Layout::set_segment_offsets): Try harder to save disk
	space.

Thanks,
-- 
Rafael Ãvila de EspÃndola

diff --git a/gold/layout.cc b/gold/layout.cc
index 5edba48..3d188a6 100644
--- a/gold/layout.cc
+++ b/gold/layout.cc
@@ -2562,7 +2562,6 @@ Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
   const bool check_sections = parameters->options().check_sections();
   Output_segment* last_load_segment = NULL;
 
-  bool was_readonly = false;
   for (Segment_list::iterator p = this->segment_list_.begin();
        p != this->segment_list_.end();
        ++p)
@@ -2609,21 +2608,17 @@ Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
 
 	  if (!are_addresses_set)
 	    {
-	      // If the last segment was readonly, and this one is
-	      // not, then skip the address forward one page,
-	      // maintaining the same position within the page.  This
-	      // lets us store both segments overlapping on a single
-	      // page in the file, but the loader will put them on
-	      // different pages in memory.
+	      // Skip the address forward one page, maintaining the same
+	      // position within the page.  This lets us store both segments
+	      // overlapping on a single page in the file, but the loader will
+	      // put them on different pages in memory. We will revisit this
+	      // decision once we know the size of the segment.
 
 	      addr = align_address(addr, (*p)->maximum_alignment());
 	      aligned_addr = addr;
 
-	      if (was_readonly && ((*p)->flags() & elfcpp::PF_W) != 0)
-		{
-		  if ((addr & (abi_pagesize - 1)) != 0)
-		    addr = addr + abi_pagesize;
-		}
+	      if ((addr & (abi_pagesize - 1)) != 0)
+                addr = addr + abi_pagesize;
 
 	      off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
 	    }
@@ -2681,9 +2676,6 @@ Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
 
 	  addr = new_addr;
 
-	  if (((*p)->flags() & elfcpp::PF_W) == 0)
-	    was_readonly = true;
-
 	  // Implement --check-sections.  We know that the segments
 	  // are sorted by LMA.
 	  if (check_sections && last_load_segment != NULL)