Fix a commit 8a8158c85e1e ("MIPS: memset.S: EVA & fault support for small_memset") regression and remove assembly warnings:
arch/mips/lib/memset.S: Assembler messages: arch/mips/lib/memset.S:243: Warning: Macro instruction expanded into multiple instructions in a branch delay slot
triggering with the CPU_DADDI_WORKAROUNDS option set and this code:
PTR_SUBU a2, t1, a0 jr ra PTR_ADDIU a2, 1
This is because with that option in place the DADDIU instruction, which the PTR_ADDIU CPP macro expands to, becomes a GAS macro, which in turn expands to an LI/DADDU (or actually ADDIU/DADDU) sequence:
13c: 01a4302f dsubu a2,t1,a0 140: 03e00008 jr ra 144: 24010001 li at,1 148: 00c1302d daddu a2,a2,at ...
Correct this by switching off the `noreorder' assembly mode and letting GAS schedule this jump's delay slot, as there is nothing special about it that would require manual scheduling. With this change in place correct code is produced:
13c: 01a4302f dsubu a2,t1,a0 140: 24010001 li at,1 144: 03e00008 jr ra 148: 00c1302d daddu a2,a2,at ...
Signed-off-by: Maciej W. Rozycki macro@linux-mips.org Fixes: 8a8158c85e1e ("MIPS: memset.S: EVA & fault support for small_memset") Cc: stable@vger.kernel.org # 4.17+ --- arch/mips/lib/memset.S | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
linux-mips-memset-jr-ra-nodaddi-fix.patch Index: linux-20180930-3maxp-defconfig/arch/mips/lib/memset.S =================================================================== --- linux-20180930-3maxp-defconfig.orig/arch/mips/lib/memset.S +++ linux-20180930-3maxp-defconfig/arch/mips/lib/memset.S @@ -280,9 +280,11 @@ * unset_bytes = end_addr - current_addr + 1 * a2 = t1 - a0 + 1 */ + .set reorder PTR_SUBU a2, t1, a0 + PTR_ADDIU a2, 1 jr ra - PTR_ADDIU a2, 1 + .set noreorder
.endm