[PR 60580, AArch64] Fix __attribute__ ((optimize("no-omit-frame-pointer")))

The implementation of -m[no-]omit-leaf-frame-pointer and
-f[no-]omit-frame-pointer in the AArch64 target does not behave
correctly in the presence of __attribute__ optimize.

This patch adjusts the implementation to work in a similar fashion to
the same functionality in the i386 target.

The problem occurs because the current implementation uses a global
'faked_omit_frame_pointer' to retain the original value of
flag_omit_frame_pointer.  The global does not form part of the
optimization save state.

This solution removes the global and instead tracks required behaviour
using only flag_omit_frame_pointer and flag_omit_leaf_frame_pointer.
These two form part of the optimziation save state and target save
state respectively.

The additional complication for AArch64 is that the PCS requires that
given -fno-omit-frame-pointer -momit-leave-frame-pointer, a leaf
function that kills LR must create a frame record.  This is readily
handled in aarch64_frame_pointer_required().  I've dropped logic in
aarch64_can_eliminate() that attempts to detect this scenario since it

From-SVN: r208862

gcc/ChangeLog

+2014-03-27  Marcus Shawcroft  <marcus.shawcroft@arm.com>
+
+	PR target/60580
+	* config/aarch64/aarch64.c (faked_omit_frame_pointer): Remove.
+	(aarch64_frame_pointer_required): Adjust logic.
+	(aarch64_can_eliminate): Adjust logic.
+	(aarch64_override_options_after_change): Adjust logic.
+
 2014-03-27  Dehao Chen  <dehao@google.com>
 
 	* ipa-inline.c (early_inliner): Update node's inline info.

gcc/config/aarch64/aarch64.c

@@ -315,10 +315,6 @@ static GTY(()) int gty_dummy;
 #define AARCH64_NUM_BITMASKS  5334
 static unsigned HOST_WIDE_INT aarch64_bitmasks[AARCH64_NUM_BITMASKS];
 
-/* Did we set flag_omit_frame_pointer just so
-   aarch64_frame_pointer_required would be called? */
-static bool faked_omit_frame_pointer;
-
 typedef enum aarch64_cond_code
 {
   AARCH64_EQ = 0, AARCH64_NE, AARCH64_CS, AARCH64_CC, AARCH64_MI, AARCH64_PL,
@@ -1694,17 +1690,15 @@ aarch64_frame_pointer_required (void)
   if (cfun->calls_alloca)
     return true;
 
-  /* We may have turned flag_omit_frame_pointer on in order to have this
-     function called; if we did, we also set the 'faked_omit_frame_pointer' flag
-     and we'll check it here.
-     If we really did set flag_omit_frame_pointer normally, then we return false
-     (no frame pointer required) in all cases.  */
+  /* In aarch64_override_options_after_change
+     flag_omit_leaf_frame_pointer turns off the frame pointer by
+     default.  Turn it back on now if we've not got a leaf
+     function.  */
+  if (flag_omit_leaf_frame_pointer
+      && (!crtl->is_leaf || df_regs_ever_live_p (LR_REGNUM)))
+    return true;
 
-  if (flag_omit_frame_pointer && !faked_omit_frame_pointer)
-    return false;
-  else if (flag_omit_leaf_frame_pointer)
-    return !crtl->is_leaf || df_regs_ever_live_p (LR_REGNUM);
-  return true;
+  return false;
 }
 
 /* Mark the registers that need to be saved by the callee and calculate
@@ -4132,23 +4126,8 @@ aarch64_can_eliminate (const int from, const int to)
 	return true;
       if (from == FRAME_POINTER_REGNUM && to == HARD_FRAME_POINTER_REGNUM)
 	return true;
-    return false;
-    }
-  else
-    {
-      /* If we decided that we didn't need a leaf frame pointer but then used
-	 LR in the function, then we'll want a frame pointer after all, so
-	 prevent this elimination to ensure a frame pointer is used.
-
-	 NOTE: the original value of flag_omit_frame_pointer gets trashed
-	 IFF flag_omit_leaf_frame_pointer is true, so we check the value
-	 of faked_omit_frame_pointer here (which is true when we always
-	 wish to keep non-leaf frame pointers but only wish to keep leaf frame
-	 pointers when LR is clobbered).  */
-      if (to == STACK_POINTER_REGNUM
-	  && df_regs_ever_live_p (LR_REGNUM)
-	  && faked_omit_frame_pointer)
-	return false;
+
+      return false;
     }
 
   return true;
@@ -5278,17 +5257,10 @@ aarch64_override_options (void)
 static void
 aarch64_override_options_after_change (void)
 {
-  faked_omit_frame_pointer = false;
-
-  /* To omit leaf frame pointers, we need to turn flag_omit_frame_pointer on so
-     that aarch64_frame_pointer_required will be called.  We need to remember
-     whether flag_omit_frame_pointer was turned on normally or just faked.  */
-
-  if (flag_omit_leaf_frame_pointer && !flag_omit_frame_pointer)
-    {
-      flag_omit_frame_pointer = true;
-      faked_omit_frame_pointer = true;
-    }
+  if (flag_omit_frame_pointer)
+    flag_omit_leaf_frame_pointer = false;
+  else if (flag_omit_leaf_frame_pointer)
+    flag_omit_frame_pointer = true;
 }
 
 static struct machine_function *

gcc/testsuite/ChangeLog

+2014-03-27  Marcus Shawcroft  <marcus.shawcroft@arm.com>
+
+	PR target/60580
+	* gcc.target/aarch64/pr60580_1.c: New.
+	* gcc.target/aarch64/test_fp_attribute_1.c: New.
+	* gcc.target/aarch64/test_fp_attribute_2.c: New.
+
 2014-03-26  Dehao Chen  <dehao@google.com>
 
 	* gcc.dg/predict-8.c: New test.

gcc/testsuite/gcc.target/aarch64/pr60580_1.c

+/* { dg-do compile } */
+/* { dg-options "-O0 -fomit-frame-pointer -fno-inline --save-temps" } */
+
+void
+func_leaf (void)
+{
+  int a = 0;
+}
+
+void
+func_no_leaf (void)
+{
+  int a = 0;
+  func_leaf ();
+}
+
+void
+func1 (void)
+{
+  int a = 0;
+  func_no_leaf ();
+}
+
+/*
+ * This function calls XXX(), which modifies SP. This is incompatible to
+ * -fomit-frame-pointer generated code as SP is used to access the frame.
+ */
+__attribute__ ((optimize("no-omit-frame-pointer")))
+void
+func2 (void)
+{
+  int a = 0;
+  func_no_leaf ();
+}
+
+void
+func3 (void)
+{
+  int a = 0;
+  func_no_leaf ();
+}
+
+/* { dg-final { scan-assembler-times "stp\tx29, x30, \\\[sp, -\[0-9\]+\\\]!" 1 } } */
+
+/* { dg-final { cleanup-saved-temps } } */

gcc/testsuite/gcc.target/aarch64/test_fp_attribute_1.c

+/* { dg-do compile } */
+/* { dg-options "-O0 -fno-omit-frame-pointer -fno-inline --save-temps" } */
+
+void
+leaf (void)
+{
+  int a = 0;
+}
+
+__attribute__ ((optimize("omit-frame-pointer")))
+void
+non_leaf_1 (void)
+{
+  leaf ();
+}
+
+__attribute__ ((optimize("omit-frame-pointer")))
+void
+non_leaf_2 (void)
+{
+  leaf ();
+}
+
+/* { dg-final { scan-assembler-times "str\tx30, \\\[sp\\\]" 2 } } */
+
+/* { dg-final { cleanup-saved-temps } } */

gcc/testsuite/gcc.target/aarch64/test_fp_attribute_2.c

+/* { dg-do compile } */
+/* { dg-options "-O0 -fomit-frame-pointer -fno-inline --save-temps" } */
+
+void
+leaf (void)
+{
+  int a = 0;
+}
+
+__attribute__ ((optimize("no-omit-frame-pointer")))
+void
+non_leaf_1 (void)
+{
+  leaf ();
+}
+
+__attribute__ ((optimize("no-omit-frame-pointer")))
+void
+non_leaf_2 (void)
+{
+  leaf ();
+}
+
+/* { dg-final { scan-assembler-times "stp\tx29, x30, \\\[sp, -\[0-9\]+\\\]!" 2 } } */
+
+/* { dg-final { cleanup-saved-temps } } */