backport i386.c regparm fix.cygming332

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/cygming332@73773 138bc75d-0d04-0410-961f-82ee72b054a4

2 files changed, 44 insertions, 15 deletions

diff --git a/gcc/ChangeLog.cygwin-mingw b/gcc/ChangeLog.cygwin-mingw
index 853a6383464..d9a3b45483b 100644
--- a/gcc/ChangeLog.cygwin-mingw
+++ b/gcc/ChangeLog.cygwin-mingw
@@ -1,3 +1,12 @@
+2003-11-20  Christopher Faylor  <cgf@redhat.com>
+
+	Backport from trunk
+	2003-10-25  Richard Henderson  <rth@redhat.com>
+
+	* config/i386/i386.c (ix86_eax_live_at_start_p): New.
+	(ix86_expand_prologue): Save and restore eax around stack probe if it's
+	live.
+
 2003-07-31  Danny Smith  <dannysmith@users.sourceforge.net>
 
 	Backport from trunk
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index b6f635db683..d04b183711c 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -1497,6 +1497,22 @@ ix86_fntype_regparm (type)
     return ix86_regparm;
 }
 
+/* Return true if EAX is live at the start of the function.  Used by 
+   ix86_expand_prologue to determine if we need special help before
+   calling allocate_stack_worker.  */
+
+static bool
+ix86_eax_live_at_start_p (void)
+{
+  /* Cheat.  Don't bother working forward from ix86_function_regparm
+     to the function type to whether an actual argument is located in
+     eax.  Instead just look at cfg info, which is still close enough
+     to correct at this point.  This gives false positives for broken
+     functions that might use uninitialized data that happens to be
+     allocated in eax, but who cares?  */
+  return REGNO_REG_SET_P (ENTRY_BLOCK_PTR->global_live_at_end, 0);
+}
+
 /* Value is the number of bytes of arguments automatically
    popped when returning from a subroutine call.
    FUNDECL is the declaration node of the function (as a tree),
@@ -4750,28 +4766,32 @@ ix86_expand_prologue ()
     }
   else
     {
-      /* ??? Is this only valid for Win32?  */
-
-      rtx arg0, sym;
+      /* Only valid for Win32.  */
+      rtx eax = gen_rtx_REG (SImode, 0);
+      bool eax_live = ix86_eax_live_at_start_p ();
 
       if (TARGET_64BIT)
-	abort ();
+        abort ();
 
-      arg0 = gen_rtx_REG (SImode, 0);
-      emit_move_insn (arg0, GEN_INT (allocate));
+      if (eax_live)
+	{
+	  emit_insn (gen_push (eax));
+	  allocate -= 4;
+	}
 
-      sym = gen_rtx_MEM (FUNCTION_MODE,
-			 gen_rtx_SYMBOL_REF (Pmode, "_alloca"));
-      insn = emit_call_insn (gen_call (sym, const0_rtx, constm1_rtx));
+      insn = emit_move_insn (eax, GEN_INT (allocate));
+      RTX_FRAME_RELATED_P (insn) = 1;
 
-      CALL_INSN_FUNCTION_USAGE (insn)
-	= gen_rtx_EXPR_LIST (VOIDmode, gen_rtx_USE (VOIDmode, arg0),
-			     CALL_INSN_FUNCTION_USAGE (insn));
+      insn = emit_insn (gen_allocate_stack_worker (eax));
+      RTX_FRAME_RELATED_P (insn) = 1;
 
-      /* Don't allow scheduling pass to move insns across __alloca
-         call.  */
-      emit_insn (gen_blockage (const0_rtx));
+      if (eax_live)
+	{
+	  rtx t = plus_constant (stack_pointer_rtx, allocate);
+	  emit_move_insn (eax, gen_rtx_MEM (SImode, t));
+	}
     }
+
   if (use_mov)
     {
       if (!frame_pointer_needed || !frame.to_allocate)