[Xen-changelog] [xen staging] xen/arm32: head: Add a macro to move an immediate constant into a 32-bit register

[patchbot@xxxxxxx]

commit 75843a162b84ff02201373d35cd2e72d7a8cca3e
Author:     Julien Grall <julien.grall@xxxxxxx>
AuthorDate: Mon Apr 15 21:58:51 2019 +0100
Commit:     Julien Grall <julien.grall@xxxxxxx>
CommitDate: Sat Sep 7 12:09:58 2019 +0100

    xen/arm32: head: Add a macro to move an immediate constant into a 32-bit 
register
    
    The current boot code is using the pattern ldr rX, =... to move an
    immediate constant into a 32-bit register.
    
    This pattern implies to load the immediate constant from a literal pool,
    meaning a memory access will be performed.
    
    The memory access can be avoided by using movw/movt instructions.
    
    A new macro is introduced to move an immediate constant into a 32-bit
    register without a memory load. Follow-up patches will make use of it.
    
    Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
    Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen/arch/arm/arm32/head.S | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index 18ded49a04..99f4af18d8 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -37,6 +37,15 @@
 #endif
 
 /*
+ * Move an immediate constant into a 32-bit register using movw/movt
+ * instructions.
+ */
+.macro mov_w reg, word
+        movw  \reg, #:lower16:\word
+        movt  \reg, #:upper16:\word
+.endm
+
+/*
  * Common register usage in this file:
  *   r0  -
  *   r1  -
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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