Constant loading of AMR_KUAP_BLOCKED takes 5 instructions:
c000000000016a40: 4c 00 01 2c isync
c000000000016a44: 3d 20 fc ff lis r9,-769
c000000000016a48: 61 29 ff ff ori r9,r9,65535
c000000000016a4c: 79 29 07 c6 rldicr r9,r9,32,31
c000000000016a50: 65 29 ff ff oris r9,r9,65535
c000000000016a54: 61 29 ff ff ori r9,r9,65535
c000000000016a58: 7d 3d 03 a6 mtamr r9
c000000000016a5c: 4c 00 01 2c isync
Until GCC is fixed, implement it in assembly using 2 instructions:
c000000000016a50: 4c 00 01 2c isync
c000000000016a54: 39 20 fc ff li r9,-769
c000000000016a58: 79 29 80 02 rotldi r9,r9,48
c000000000016a5c: 7d 3d 03 a6 mtamr r9
c000000000016a60: 4c 00 01 2c isync
With this change a ppc64_defconfig build is reduced by 15 kbytes.
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94395
Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu>
---
arch/powerpc/include/asm/book3s/64/kup.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/powerpc/include/asm/book3s/64/kup.h
b/arch/powerpc/include/asm/book3s/64/kup.h
index 54cf46808157..35c017ba29e1 100644
--- a/arch/powerpc/include/asm/book3s/64/kup.h
+++ b/arch/powerpc/include/asm/book3s/64/kup.h
@@ -338,6 +338,10 @@ static __always_inline void set_kuap(unsigned long value)
* before and after the move to AMR. See table 6 on page 1134.
*/
isync();
+
+ if (__builtin_constant_p(value) && value == 0xfcffffffffffffff)
+ asm("li %0, %1 ; rotldi %0, %0, 48" : "=r"(value) :
"i"(0xfffffffffffffcff));
+
mtspr(SPRN_AMR, value);
isync();
}
--
2.34.1
