MIPS: Fix BC1{EQ,NE}Z return offset calculation

[Paul Burton <paulburton@xxxxxxxxxx>]

From: Paul Burton <paul.burton@xxxxxxxxxx>

commit ac1496980f1d2752f26769f5db63afbc9ac2b603 upstream.

The conditions for branching when emulating the BC1EQZ & BC1NEZ
instructions were backwards, leading to each of those instructions being
treated as the other. Fix this by reversing the conditions, and clear up
the code a little for readability & checkpatch.

Fixes: c8a34581ec09 ("MIPS: Emulate the BC1{EQ,NE}Z FPU instructions")
Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx>
Reviewed-by: James Hogan <james.hogan@xxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/13151/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/mips/kernel/branch.c |   18 +++---------------
 1 file changed, 3 insertions(+), 15 deletions(-)

--- a/arch/mips/kernel/branch.c
+++ b/arch/mips/kernel/branch.c
@@ -685,21 +685,9 @@ int __compute_return_epc_for_insn(struct
 			}
 			lose_fpu(1);    /* Save FPU state for the emulator. */
 			reg = insn.i_format.rt;
-			bit = 0;
-			switch (insn.i_format.rs) {
-			case bc1eqz_op:
-				/* Test bit 0 */
-				if (get_fpr32(&current->thread.fpu.fpr[reg], 0)
-				    & 0x1)
-					bit = 1;
-				break;
-			case bc1nez_op:
-				/* Test bit 0 */
-				if (!(get_fpr32(&current->thread.fpu.fpr[reg], 0)
-				      & 0x1))
-					bit = 1;
-				break;
-			}
+			bit = get_fpr32(&current->thread.fpu.fpr[reg], 0) & 0x1;
+			if (insn.i_format.rs == bc1eqz_op)
+				bit = !bit;
 			own_fpu(1);
 			if (bit)
 				epc = epc + 4 +


Patches currently in stable-queue which might be from paulburton@xxxxxxxxxx are

queue-4.4/mips-math-emu-fix-bc1-eq-ne-z-emulation.patch
queue-4.4/mips-smp-cps-stop-printing-ejtag-exceptions-to-uart.patch
queue-4.4/mips-fix-bc1-eq-ne-z-return-offset-calculation.patch
queue-4.4/mips-math-emu-fix-m-add-sub-.s-shifts.patch