PATCH: Properly generate X32 IE sequence

[Uros Bizjak]

On Sun, Mar 11, 2012 at 10:24 PM, H.J. Lu <hjl.tools@gmail.com> wrote:

> Here is the patch which is equivalent to clearing MASK_TLS_DIRECT_SEG_REFS
> when Pmode != word_mode.  We need to keep
>
>          else if (Pmode == SImode)
>            {
>              /* Always generate
>                        movl %fs:0, %reg32
>                        addl xgottpoff(%rip), %reg32
>                 to support linker IE->LE optimization and avoid
>                 fs:(%reg32) as memory operand.  */
>              dest = gen_reg_rtx (Pmode);
>              emit_insn (gen_tls_initial_exec_x32 (dest, x));
>              return dest;
>            }
>
> to support linker IE->LE optimization.  TARGET_TLS_DIRECT_SEG_REFS only affects
> TLS LE access and fs:(%reg) is only generated by combine.
>
> So the main impact of disabling TARGET_TLS_DIRECT_SEG_REFS is to disable
> fs:immediate memory operand for TLS LE access, which doesn't have any problems
> to begin with.
>
> I would prefer to keep TARGET_TLS_DIRECT_SEG_REFS and disable only
> fs:(%reg), which is generated by combine.

Please try attached patch.  It introduces TARGET_TLS_INDIRECT_SEG_REFS
to block only indirect seg references.

Uros.
-------------- next part --------------
Index: i386.c
===================================================================
--- i386.c	(revision 185250)
+++ i386.c	(working copy)
@@ -11552,11 +11552,6 @@ ix86_decompose_address (rtx addr, struct ix86_addr
   else
     disp = addr;			/* displacement */
 
-  /* Since address override works only on the (reg32) part in fs:(reg32),
-     we can't use it as memory operand.  */
-  if (Pmode != word_mode && seg == SEG_FS && (base || index))
-    return 0;
-
   if (index)
     {
       if (REG_P (index))
@@ -11568,6 +11563,10 @@ ix86_decompose_address (rtx addr, struct ix86_addr
 	return 0;
     }
 
+  if (seg != SEG_DEFAULT && (base || index)
+      && !TARGET_TLS_INDIRECT_SEG_REFS)
+    return 0;
+
   /* Extract the integral value of scale.  */
   if (scale_rtx)
     {
@@ -12696,7 +12695,9 @@ legitimize_tls_address (rtx x, enum tls_model mode
 
       if (TARGET_64BIT || TARGET_ANY_GNU_TLS)
 	{
-          base = get_thread_pointer (for_mov || !TARGET_TLS_DIRECT_SEG_REFS);
+          base = get_thread_pointer (for_mov
+				     || !(TARGET_TLS_DIRECT_SEG_REFS
+					  && TARGET_TLS_INDIRECT_SEG_REFS));
 	  off = force_reg (Pmode, off);
 	  return gen_rtx_PLUS (Pmode, base, off);
 	}
@@ -12716,7 +12717,9 @@ legitimize_tls_address (rtx x, enum tls_model mode
 
       if (TARGET_64BIT || TARGET_ANY_GNU_TLS)
 	{
-	  base = get_thread_pointer (for_mov || !TARGET_TLS_DIRECT_SEG_REFS);
+	  base = get_thread_pointer (for_mov
+				     || !(TARGET_TLS_DIRECT_SEG_REFS
+					  && TARGET_TLS_INDIRECT_SEG_REFS));
 	  return gen_rtx_PLUS (Pmode, base, off);
 	}
       else
@@ -13249,7 +13252,8 @@ ix86_delegitimize_tls_address (rtx orig_x)
   rtx x = orig_x, unspec;
   struct ix86_address addr;
 
-  if (!TARGET_TLS_DIRECT_SEG_REFS)
+  if (!(TARGET_TLS_DIRECT_SEG_REFS
+	&& TARGET_TLS_INDIRECT_SEG_REFS))
     return orig_x;
   if (MEM_P (x))
     x = XEXP (x, 0);
Index: i386.h
===================================================================
--- i386.h	(revision 185250)
+++ i386.h	(working copy)
@@ -467,6 +467,9 @@ extern int x86_prefetch_sse;
 #define TARGET_TLS_DIRECT_SEG_REFS_DEFAULT 0
 #endif
 
+/* Address override works only on the (%reg) part in %fs:(%reg).  */
+#define TARGET_TLS_INDIRECT_SEG_REFS (Pmode == word_mode)
+
 /* Fence to use after loop using storent.  */
 
 extern tree x86_mfence;