MIPS: math-emu: Fix BC1EQZ and BC1NEZ condition handling

Correct the treatment of branching conditions for BC1EQZ and BC1NEZ
instructions in function isBranchInstr().

Previously, corresponding conditions were swapped, which in turn meant
that, for these two instructions, function isBranchInstr() returned
wrong value in its output parameter contpc.

This change is actually an extension of the fix done by the commit
93583e178ebf ("MIPS: math-emu: Fix BC1{EQ,NE}Z emulation"). That commit
dealt with a similar problem in function cop1Emulate(), while this
commit deals with condition handling in function isBranchInstr().
The code styles of changes in these two commits are kept as
consistent as possible.

Signed-off-by: Douglas Leung <douglas.leung@imgtec.com>
Signed-off-by: Miodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
Reviewed-by: Paul Burton <paul.burton@imgtec.com>
Cc: james.hogan@imgtec.com
Cc: leonid.yegoshin@imgtec.com
Cc: petar.jovanovic@imgtec.com
Cc: goran.ferenc@imgtec.com
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15489/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/math-emu/cp1emu.c

@@ -439,6 +439,8 @@ int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
 	union mips_instruction insn = (union mips_instruction)dec_insn.insn;
 	unsigned int fcr31;
 	unsigned int bit = 0;
+	unsigned int bit0;
+	union fpureg *fpr;
 
 	switch (insn.i_format.opcode) {
 	case spec_op:
@@ -706,14 +708,14 @@ int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
 		    ((insn.i_format.rs == bc1eqz_op) ||
 		     (insn.i_format.rs == bc1nez_op))) {
 			bit = 0;
+			fpr = &current->thread.fpu.fpr[insn.i_format.rt];
+			bit0 = get_fpr32(fpr, 0) & 0x1;
 			switch (insn.i_format.rs) {
 			case bc1eqz_op:
-				if (get_fpr32(&current->thread.fpu.fpr[insn.i_format.rt], 0) & 0x1)
-				    bit = 1;
+				bit = bit0 == 0;
 				break;
 			case bc1nez_op:
-				if (!(get_fpr32(&current->thread.fpu.fpr[insn.i_format.rt], 0) & 0x1))
-				    bit = 1;
+				bit = bit0 != 0;
 				break;
 			}
 			if (bit)