From patchwork Thu Jun 14 23:21:29 2012
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Subject: ARM: exclude fixed_regs for stack-alignment save/restore
Date: Thu, 14 Jun 2012 13:21:29 -0000
From: Roland McGrath <mcgrathr@google.com>
X-Patchwork-Id: 165026
Message-Id: <CAB=4xhpNuPf_T+HHysBPzThLRhhjvJ9BmVjQ2YqQpjheZff0oA@mail.gmail.com>
To: Mike Stump <mikestump@comcast.net>
Cc: gcc-patches@gcc.gnu.org

Here's the version of the change that incorporates Mike's suggestion.


Thanks,
Roland


gcc/
2012-06-14  Roland McGrath  <mcgrathr@google.com>

	* config/arm/arm.c (arm_get_frame_offsets): Never use a fixed register
	as the extra register to save/restore for stack-alignment padding.


diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 092e202..13771d9 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -16752,7 +16752,12 @@ arm_get_frame_offsets (void)
 	  else
 	    for (i = 4; i <= (TARGET_THUMB1 ? LAST_LO_REGNUM : 11); i++)
 	      {
-		if ((offsets->saved_regs_mask & (1 << i)) == 0)
+		/* While the gratuitous register save/restore is ordinarily
+		   harmless, if a register is marked as fixed or global it
+		   may be entirely forbidden by the system ABI to touch it,
+		   so we should avoid those registers.  */
+		if (!fixed_regs[i] && !global_regs[i]
+		    && (offsets->saved_regs_mask & (1 << i)) == 0)
 		  {
 		    reg = i;
 		    break;