From: Tamar Christina <tamar.christina@arm.com>
Date: Mon, 8 Jun 2020 08:23:10 +0000 (+0100)
Subject: AArch64: Expand on comment of stack-clash and implicit probing through LR.
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=d6430e3cccb37bec6c5604dffe48c52016509013;p=gcc.git

AArch64: Expand on comment of stack-clash and implicit probing through LR.

This expands the comment on an assert we have in aarch64_layout_frame
and points to an existing comment somewhere else that has a much longer
explanation of what's going on.

Committed under the GCC Obvious rule.

gcc/ChangeLog:

	* config/aarch64/aarch64.c (aarch64_layout_frame): Expand comments.
---

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 97da6076239..973c65aa4fb 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -6531,7 +6531,9 @@ aarch64_layout_frame (void)
 	&& !crtl->abi->clobbers_full_reg_p (regno))
       frame.reg_offset[regno] = SLOT_REQUIRED;
 
-  /* With stack-clash, LR must be saved in non-leaf functions.  */
+  /* With stack-clash, LR must be saved in non-leaf functions.  The saving of
+     LR counts as an implicit probe which allows us to maintain the invariant
+     described in the comment at expand_prologue.  */
   gcc_assert (crtl->is_leaf
 	      || maybe_ne (frame.reg_offset[R30_REGNUM], SLOT_NOT_REQUIRED));