Subject: [PATCH v4 5/5] powerpc/lib/sstep: Add isel instruction emulation

From: Matt Brown <[email-masked]>
Date: Mon, 31 Jul 2017 10:58:26 +1000

This adds emulation for the isel instruction.
Tested for correctness against the isel instruction and its extended
mnemonics (lt, gt, eq) on ppc64le.

Signed-off-by: Matt Brown <[email-masked]>
---
v4:
	- simplify if statement to ternary op
	(same as isel emulation in kernel/traps.c)
v2:
	- fixed opcode
	- fixed definition to include the 'if RA=0, a=0' clause
	- fixed ccr bitshifting error
---
 arch/powerpc/lib/sstep.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index af4eef9..473bab5 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -1240,6 +1240,14 @@ int analyse_instr(struct instruction_op *op, struct pt_regs *regs,
 /*
  * Logical instructions
  */
+		case 15:	/* isel */
+			mb = (instr >> 6) & 0x1f; /* bc */
+			val = (regs->ccr >> (31 - mb)) & 1;
+			val2 = (ra) ? regs->gpr[ra] : 0;
+
+			regs->gpr[rd] = (val) ? val2 : regs->gpr[rb];
+			goto logical_done;
+
 		case 26:	/* cntlzw */
 			asm("cntlzw %0,%1" : "=r" (regs->gpr[ra]) :
 			    "r" (regs->gpr[rd]));
-- 
2.9.3