[PATCH v4 4/5] powerpc/lib/sstep: Add prty instruction emulation

[Matt Brown <matthew.brown.dev@gmail.com>]

This adds emulation for the prtyw and prtyd instructions.
Tested for logical correctness against the prtyw and prtyd instructions
on ppc64le.

Signed-off-by: Matt Brown <matthew.brown.dev@gmail.com>
---
v4:
	- use simpler xor method
v3:
	- optimised using the Giles-Miller method of side-ways addition
v2:
	- fixed opcodes
	- fixed bitshifting and typecast errors
	- merged do_prtyw and do_prtyd into single function
---
 arch/powerpc/lib/sstep.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index c9fd613..af4eef9 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -657,6 +657,24 @@ static nokprobe_inline void do_bpermd(struct pt_regs *regs, unsigned long v1,
 	regs->gpr[ra] = perm;
 }
 #endif /* CONFIG_PPC64 */
+/*
+ * The size parameter adjusts the equivalent prty instruction.
+ * prtyw = 32, prtyd = 64
+ */
+static nokprobe_inline void do_prty(struct pt_regs *regs, unsigned long v,
+				int size, int ra)
+{
+	unsigned long long res = v ^ (v >> 8);
+
+	res ^= res >> 16;
+	if (size == 32) {		/* prtyw */
+		regs->gpr[ra] = res & 0x0000000100000001;
+		return;
+	}
+
+	res ^= res >> 32;
+	regs->gpr[ra] = res & 1;	/*prtyd */
+}
 
 static nokprobe_inline int trap_compare(long v1, long v2)
 {
@@ -1247,6 +1265,14 @@ int analyse_instr(struct instruction_op *op, struct pt_regs *regs,
 		case 124:	/* nor */
 			regs->gpr[ra] = ~(regs->gpr[rd] | regs->gpr[rb]);
 			goto logical_done;
+
+		case 154:	/* prtyw */
+			do_prty(regs, regs->gpr[rd], 32, ra);
+			goto logical_done;
+
+		case 186:	/* prtyd */
+			do_prty(regs, regs->gpr[rd], 64, ra);
+			goto logical_done;
 #ifdef CONFIG_PPC64
 		case 252:	/* bpermd */
 			do_bpermd(regs, regs->gpr[rd], regs->gpr[rb], ra);
-- 
2.9.3