diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index fa9af26..2e69a4d 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -284,11 +284,13 @@ extern unsigned aarch64_architecture_version;
 
 /* Standard register usage.  */
 
+#define FIXED_R18 0
+
 /* 31 64-bit general purpose registers R0-R30:
    R30		LR (link register)
    R29		FP (frame pointer)
    R19-R28	Callee-saved registers
-   R18		The platform register; use as temporary register.
+   R18		The platform register; use as temporary register if !FIXED_R18.
    R17		IP1 The second intra-procedure-call temporary register
 		(can be used by call veneers and PLT code); otherwise use
 		as a temporary register
@@ -324,7 +326,7 @@ extern unsigned aarch64_architecture_version;
   {							\
     0, 0, 0, 0,   0, 0, 0, 0,	/* R0 - R7 */		\
     0, 0, 0, 0,   0, 0, 0, 0,	/* R8 - R15 */		\
-    0, 0, 0, 0,   0, 0, 0, 0,	/* R16 - R23 */		\
+    0, 0, FIXED_R18, 0, 0, 0, 0, 0,	/* R16 - R23 */		\
     0, 0, 0, 0,   0, 1, 0, 1,	/* R24 - R30, SP */	\
     0, 0, 0, 0,   0, 0, 0, 0,   /* V0 - V7 */           \
     0, 0, 0, 0,   0, 0, 0, 0,   /* V8 - V15 */		\
@@ -419,7 +421,7 @@ extern unsigned aarch64_architecture_version;
    uses alloca.  */
 #define EXIT_IGNORE_STACK	(cfun->calls_alloca)
 
-#define STATIC_CHAIN_REGNUM		R18_REGNUM
+#define STATIC_CHAIN_REGNUM		(!(FIXED_R18) ? R18_REGNUM : R11_REGNUM)
 #define HARD_FRAME_POINTER_REGNUM	R29_REGNUM
 #define FRAME_POINTER_REGNUM		SFP_REGNUM
 #define STACK_POINTER_REGNUM		SP_REGNUM