From: Wilco Dijkstra <wdijkstr@arm.com>
Date: Thu, 26 Oct 2017 16:40:25 +0000 (+0000)
Subject: Simplify frame layout for stack probing
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=1f7bffd09412d801016ecd014f34db77da2cc63e;p=gcc.git

Simplify frame layout for stack probing

This patch makes some changes to the frame layout in order to simplify
stack probing.  We want to use the save of LR as a probe in any non-leaf
function.  With shrinkwrapping we may only save LR before a call, so it
is useful to define a fixed location in the callee-saves. So force LR at
the bottom of the callee-saves even with -fomit-frame-pointer.

Also remove a rarely used frame layout that saves the callee-saves first
with -fomit-frame-pointer.  Doing so allows the store of LR to be used as
a valid stack probe in all frames.

    gcc/
	* config/aarch64/aarch64.c (aarch64_layout_frame):
        Ensure LR is always stored at the bottom of the callee-saves.
        Remove rarely used frame layout which saves callee-saves at top of
        frame, so the store of LR can be used as a valid probe in all cases.

From-SVN: r254112
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 7e0417ba60c..f32a30b7730 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2017-10-26  Wilco Dijkstra  <wdijkstr@arm.com>
+
+	* config/aarch64/aarch64.c (aarch64_layout_frame):
+	Ensure LR is always stored at the bottom of the callee-saves.
+	Remove rarely used frame layout which saves callee-saves at top of
+	frame, so the store of LR can be used as a valid probe in all cases.
+
 2017-10-26  Wilco Dijkstra  <wdijkstr@arm.com>
 
 	* config/aarch64/aarch64.c (aarch64_legitimize_address_displacement):
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 83630fce1cc..ed97e2d5de1 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -2885,7 +2885,8 @@ aarch64_frame_pointer_required (void)
 
 /* Mark the registers that need to be saved by the callee and calculate
    the size of the callee-saved registers area and frame record (both FP
-   and LR may be omitted).  */
+   and LR may be omitted).  If the function is not a leaf, ensure LR is
+   saved at the bottom of the callee-save area.  */
 static void
 aarch64_layout_frame (void)
 {
@@ -2936,7 +2937,14 @@ aarch64_layout_frame (void)
       cfun->machine->frame.wb_candidate1 = R29_REGNUM;
       cfun->machine->frame.reg_offset[R30_REGNUM] = UNITS_PER_WORD;
       cfun->machine->frame.wb_candidate2 = R30_REGNUM;
-      offset += 2 * UNITS_PER_WORD;
+      offset = 2 * UNITS_PER_WORD;
+    }
+  else if (!crtl->is_leaf)
+    {
+      /* Ensure LR is saved at the bottom of the callee-saves.  */
+      cfun->machine->frame.reg_offset[R30_REGNUM] = 0;
+      cfun->machine->frame.wb_candidate1 = R30_REGNUM;
+      offset = UNITS_PER_WORD;
     }
 
   /* Now assign stack slots for them.  */
@@ -3035,20 +3043,6 @@ aarch64_layout_frame (void)
       cfun->machine->frame.final_adjust
 	= cfun->machine->frame.frame_size - cfun->machine->frame.callee_adjust;
     }
-  else if (!frame_pointer_needed
-	   && varargs_and_saved_regs_size < max_push_offset)
-    {
-      /* Frame with large local area and outgoing arguments (this pushes the
-	 callee-saves first, followed by the locals and outgoing area):
-	 stp reg1, reg2, [sp, -varargs_and_saved_regs_size]!
-	 stp reg3, reg4, [sp, 16]
-	 sub sp, sp, frame_size - varargs_and_saved_regs_size  */
-      cfun->machine->frame.callee_adjust = varargs_and_saved_regs_size;
-      cfun->machine->frame.final_adjust
-	= cfun->machine->frame.frame_size - cfun->machine->frame.callee_adjust;
-      cfun->machine->frame.hard_fp_offset = cfun->machine->frame.callee_adjust;
-      cfun->machine->frame.locals_offset = cfun->machine->frame.hard_fp_offset;
-    }
   else
     {
       /* Frame with large local area and outgoing arguments using frame pointer: