PATCH: PR target/63815: [5 Regression] g++.dg/other/pr53811.C fails with -mcmodel=large -fpic

[H.J. Lu]

Hi,

r216154 exposed an x86 backend bug.  For large PIC mode thunk, there
are

      if (ix86_cmodel == CM_LARGE_PIC && SYMBOLIC_CONST (fnaddr))
        fnaddr = legitimize_pic_address (fnaddr,
                                         gen_rtx_REG (Pmode, tmp_regno));

and legitimize_pic_address does:

      if (reg != 0)
        {
          new_rtx = expand_simple_binop (Pmode, PLUS, reg, pic_offset_table_rtx,
                                         tmpreg, 1, OPTAB_DIRECT);
          new_rtx = reg;
        }

However, pic_offset_table_rtx was never initialized.  Befor r216154,
we generated thunk with random value in hardcoded PIC register.  After
r216154, compiler crashes.  This patch sets PIC register to %r11 and
initialize it.  Tested on Linux/x86-64.  OK for trunk and backport 
to 4.8/4.9 branches?

Thanks.


H.J.
---
gcc/

2014-11-12  H.J. Lu  <hongjiu...@intel.com>

        PR target/63815
        * config/i386/i386.c (ix86_init_large_pic_reg): New.  Extracted
        from ...
        (ix86_init_pic_reg): Here.  Use ix86_init_large_pic_reg.
        (x86_output_mi_thunk): Set PIC register to %r11.  Call
        ix86_init_large_pic_reg to initialize PIC register.

gcc/testsuite/

2014-11-12  H.J. Lu  <hongjiu...@intel.com>

        PR target/63815
        * g++.dg/other/pr63815.C: New test.

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 2866900..0bd3ff3 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -6195,6 +6195,27 @@ ix86_use_pseudo_pic_reg (void)
   return true;
 }
 
+/* Initialize large model PIC register.  */
+
+static void
+ix86_init_large_pic_reg (unsigned int tmp_regno)
+{
+  rtx_code_label *label;
+  rtx tmp_reg;
+
+  gcc_assert (Pmode == DImode);
+  label = gen_label_rtx ();
+  emit_label (label);
+  LABEL_PRESERVE_P (label) = 1;
+  tmp_reg = gen_rtx_REG (Pmode, tmp_regno);
+  gcc_assert (REGNO (pic_offset_table_rtx) != tmp_regno);
+  emit_insn (gen_set_rip_rex64 (pic_offset_table_rtx,
+                               label));
+  emit_insn (gen_set_got_offset_rex64 (tmp_reg, label));
+  emit_insn (ix86_gen_add3 (pic_offset_table_rtx,
+                           pic_offset_table_rtx, tmp_reg));
+}
+
 /* Create and initialize PIC register if required.  */
 static void
 ix86_init_pic_reg (void)
@@ -6210,22 +6231,7 @@ ix86_init_pic_reg (void)
   if (TARGET_64BIT)
     {
       if (ix86_cmodel == CM_LARGE_PIC)
-       {
-         rtx_code_label *label;
-         rtx tmp_reg;
-
-         gcc_assert (Pmode == DImode);
-         label = gen_label_rtx ();
-         emit_label (label);
-         LABEL_PRESERVE_P (label) = 1;
-         tmp_reg = gen_rtx_REG (Pmode, R11_REG);
-         gcc_assert (REGNO (pic_offset_table_rtx) != REGNO (tmp_reg));
-         emit_insn (gen_set_rip_rex64 (pic_offset_table_rtx,
-                                       label));
-         emit_insn (gen_set_got_offset_rex64 (tmp_reg, label));
-         emit_insn (ix86_gen_add3 (pic_offset_table_rtx,
-                                   pic_offset_table_rtx, tmp_reg));
-       }
+       ix86_init_large_pic_reg (R11_REG);
       else
        emit_insn (gen_set_got_rex64 (pic_offset_table_rtx));
     }
@@ -42686,8 +42692,12 @@ x86_output_mi_thunk (FILE *file, tree, HOST_WIDE_INT 
delta,
   else
     {
       if (ix86_cmodel == CM_LARGE_PIC && SYMBOLIC_CONST (fnaddr))
-       fnaddr = legitimize_pic_address (fnaddr,
-                                        gen_rtx_REG (Pmode, tmp_regno));
+       {
+         SET_REGNO (pic_offset_table_rtx, R11_REG);
+         ix86_init_large_pic_reg (tmp_regno);
+         fnaddr = legitimize_pic_address (fnaddr,
+                                          gen_rtx_REG (Pmode, tmp_regno));
+       }
 
       if (!sibcall_insn_operand (fnaddr, word_mode))
        {
diff --git a/gcc/testsuite/g++.dg/other/pr63815.C 
b/gcc/testsuite/g++.dg/other/pr63815.C
new file mode 100644
index 0000000..fce6226
--- /dev/null
+++ b/gcc/testsuite/g++.dg/other/pr63815.C
@@ -0,0 +1,50 @@
+// PR target/63815
+// { dg-do run { target { { i?86-*-linux* x86_64-*-linux* } && lp64 } } }
+// { dg-options "-mcmodel=large" }
+// { dg-additional-options "-fpic" { target fpic } }
+
+struct ICCStringClass
+{
+  virtual int CreateString (int) = 0;
+};
+
+struct AGSCCDynamicObject
+{
+  virtual void Unserialize () = 0;
+};
+
+struct ScriptString:AGSCCDynamicObject, ICCStringClass
+{
+  virtual int CreateString (int);
+  virtual void Unserialize ();
+};
+
+int
+__attribute__ ((noinline))
+CreateNewScriptString (int fromText, bool reAllocate = true)
+{
+  return fromText;
+}
+
+int
+__attribute__ ((noinline))
+ScriptString::CreateString (int fromText)
+{
+  return CreateNewScriptString (fromText);
+}
+
+void
+__attribute__ ((noinline))
+ScriptString::Unserialize ()
+{
+}
+
+int
+main ()
+{
+  ICCStringClass *x = new ScriptString;
+
+  if (x->CreateString (1) != 1)
+    __builtin_abort ();
+  return 0;
+}