http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40718
http://bugs.gentoo.org/show_bug.cgi?id=282189
svn diff -r151029:151030 > pr151030.patch

Index: gcc/testsuite/gcc.target/i386/pr40718.c
===================================================================
--- gcc/testsuite/gcc.target/i386/pr40718.c	(revision 0)
+++ gcc/testsuite/gcc.target/i386/pr40718.c	(revision 151030)
@@ -0,0 +1,36 @@
+/* { dg-do run } */
+/* { dg-require-effective-target ilp32 } */
+/* { dg-options "-O1 -foptimize-sibling-calls" } */
+
+void abort (void);
+
+struct S
+{
+  void (__attribute__((__stdcall__)) *f) (struct S *);
+  int i;
+};
+
+void __attribute__((__stdcall__))
+foo (struct S *s)
+{
+  s->i++;
+}
+
+void __attribute__((__stdcall__))
+bar (struct S *s)
+{
+  foo(s);
+  s->f(s);
+}
+
+int main (void)
+{
+  struct S s = { foo, 0 };
+
+  bar (&s);
+  if (s.i != 2)
+    abort ();
+
+  return 0;
+}
+
Index: gcc/config/i386/i386.md
===================================================================
--- gcc/config/i386/i386.md	(revision 151029)
+++ gcc/config/i386/i386.md	(revision 151030)
@@ -14973,22 +14973,25 @@
 	 (match_operand:SI 1 "" ""))
    (set (reg:SI SP_REG) (plus:SI (reg:SI SP_REG)
 			    (match_operand:SI 2 "immediate_operand" "i")))]
-  "!TARGET_64BIT"
+  "!SIBLING_CALL_P (insn) && !TARGET_64BIT"
 {
   if (constant_call_address_operand (operands[0], Pmode))
-    {
-      if (SIBLING_CALL_P (insn))
-	return "jmp\t%P0";
-      else
-	return "call\t%P0";
-    }
-  if (SIBLING_CALL_P (insn))
-    return "jmp\t%A0";
-  else
-    return "call\t%A0";
+    return "call\t%P0";
+  return "call\t%A0";
 }
   [(set_attr "type" "call")])
 
+(define_insn "*sibcall_pop_1"
+  [(call (mem:QI (match_operand:SI 0 "sibcall_insn_operand" "s,U"))
+	 (match_operand:SI 1 "" ""))
+   (set (reg:SI SP_REG) (plus:SI (reg:SI SP_REG)
+			    (match_operand:SI 2 "immediate_operand" "i,i")))]
+  "SIBLING_CALL_P (insn) && !TARGET_64BIT"
+  "@
+   jmp\t%P0
+   jmp\t%A0"
+  [(set_attr "type" "call")])
+
 (define_expand "call"
   [(call (match_operand:QI 0 "" "")
 	 (match_operand 1 "" ""))
@@ -21469,22 +21472,26 @@
 	      (match_operand:SI 2 "" "")))
    (set (reg:SI SP_REG) (plus:SI (reg:SI SP_REG)
 			    (match_operand:SI 3 "immediate_operand" "i")))]
-  "!TARGET_64BIT"
+  "!SIBLING_CALL_P (insn) && !TARGET_64BIT"
 {
   if (constant_call_address_operand (operands[1], Pmode))
-    {
-      if (SIBLING_CALL_P (insn))
-	return "jmp\t%P1";
-      else
-	return "call\t%P1";
-    }
-  if (SIBLING_CALL_P (insn))
-    return "jmp\t%A1";
-  else
-    return "call\t%A1";
+    return "call\t%P1";
+  return "call\t%A1";
 }
   [(set_attr "type" "callv")])
 
+(define_insn "*sibcall_value_pop_1"
+  [(set (match_operand 0 "" "")
+	(call (mem:QI (match_operand:SI 1 "call_insn_operand" "s,U"))
+	      (match_operand:SI 2 "" "")))
+   (set (reg:SI SP_REG) (plus:SI (reg:SI SP_REG)
+			    (match_operand:SI 3 "immediate_operand" "i,i")))]
+  "SIBLING_CALL_P (insn) && !TARGET_64BIT"
+  "@
+   jmp\t%P1
+   jmp\t%A1"
+  [(set_attr "type" "callv")])
+
 (define_insn "*call_value_0"
   [(set (match_operand 0 "" "")
 	(call (mem:QI (match_operand:SI 1 "constant_call_address_operand" ""))