[gcc r12-5008] Fix couple of issues in large PIC model on x86-64/VxWorks

[Eric Botcazou <ebotcazou@gcc.gnu.org>]

https://gcc.gnu.org/g:6c5fffd127ec00038f379773f751bf803bc548b0

commit r12-5008-g6c5fffd127ec00038f379773f751bf803bc548b0
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Mon Nov 8 22:09:16 2021 +0100

    Fix couple of issues in large PIC model on x86-64/VxWorks
    
    The first issue is that the !gotoff_operand path of legitimize_pic_address
    in the large PIC model does not make use of REG when it is available, which
    breaks for thunks because new pseudo-registers can no longer be created.
    And the second issue is that the system compiler (LLVM) generates @GOTOFF
    in large model even for RTP, so we do the same.
    
    gcc/
            * config/i386/i386.c (legitimize_pic_address): Adjust comment and
            use the REG argument on the CM_LARGE_PIC code path as well.
            * config/i386/predicates.md (gotoff_operand): Do not treat VxWorks
            specially with the large code models.

Diff:
---
 gcc/config/i386/i386.c        | 16 +++++++++++++---
 gcc/config/i386/predicates.md |  6 ++++--
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 96635d6858f..e94efdf39fb 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -11161,7 +11161,7 @@ legitimize_pic_address (rtx orig, rtx reg)
 	new_rtx = gen_rtx_PLUS (Pmode, pic_offset_table_rtx, new_rtx);
     }
   else if ((GET_CODE (addr) == SYMBOL_REF && SYMBOL_REF_TLS_MODEL (addr) == 0)
-	   /* We can't use @GOTOFF for text labels
+	   /* We can't always use @GOTOFF for text labels
 	      on VxWorks, see gotoff_operand.  */
 	   || (TARGET_VXWORKS_RTP && GET_CODE (addr) == LABEL_REF))
     {
@@ -11190,9 +11190,19 @@ legitimize_pic_address (rtx orig, rtx reg)
 	     from the Global Offset Table (@GOT).  */
 	  new_rtx = gen_rtx_UNSPEC (Pmode, gen_rtvec (1, addr), UNSPEC_GOT);
 	  new_rtx = gen_rtx_CONST (Pmode, new_rtx);
+
 	  if (TARGET_64BIT)
-	    new_rtx = force_reg (Pmode, new_rtx);
-	  new_rtx = gen_rtx_PLUS (Pmode, pic_offset_table_rtx, new_rtx);
+	    new_rtx = copy_to_suggested_reg (new_rtx, reg, Pmode);
+
+	  if (reg != 0)
+	    {
+	      gcc_assert (REG_P (reg));
+	      new_rtx = expand_simple_binop (Pmode, PLUS, pic_offset_table_rtx,
+					     new_rtx, reg, 1, OPTAB_DIRECT);
+	    }
+	  else
+	    new_rtx = gen_rtx_PLUS (Pmode, pic_offset_table_rtx, new_rtx);
+
 	  new_rtx = gen_const_mem (Pmode, new_rtx);
 	  set_mem_alias_set (new_rtx, ix86_GOT_alias_set ());
 	}
diff --git a/gcc/config/i386/predicates.md b/gcc/config/i386/predicates.md
index 114d8d448f1..4ccbe11b842 100644
--- a/gcc/config/i386/predicates.md
+++ b/gcc/config/i386/predicates.md
@@ -617,9 +617,11 @@
 ;; use @GOTOFF unless we are absolutely sure that the symbol is in the
 ;; same segment as the GOT.  Unfortunately, the flexibility of linker
 ;; scripts means that we can't be sure of that in general, so assume
-;; that @GOTOFF is never valid on VxWorks.
+;; @GOTOFF is not valid on VxWorks, except with the large code model.
 (define_predicate "gotoff_operand"
-  (and (not (match_test "TARGET_VXWORKS_RTP"))
+  (and (ior (not (match_test "TARGET_VXWORKS_RTP"))
+            (match_test "ix86_cmodel == CM_LARGE")
+            (match_test "ix86_cmodel == CM_LARGE_PIC"))
        (match_operand 0 "local_symbolic_operand")))
 
 ;; Test for various thread-local symbols.