[PATCH] [POWERPC] Emulate isel (Integer Select) instruction

[Kumar Gala <galak@kernel.crashing.org>]

isel (Integer Select) is a new user space instruction in the
PowerISA 2.04 spec.  Not all processors implement it so lets emulate
to ensure code built with isel will run everywhere.

---
 arch/powerpc/kernel/traps.c |   25 +++++++++++++++++++++++++
 1 files changed, 25 insertions(+), 0 deletions(-)

In my git tree for 2.6.25.

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 59c464e..cad6484 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -622,6 +622,9 @@ static void parse_fpe(struct pt_regs *regs)
 #define INST_POPCNTB		0x7c0000f4
 #define INST_POPCNTB_MASK	0xfc0007fe

+#define INST_ISEL		0x7c00001e
+#define INST_ISEL_MASK		0xfc00003e
+
 static int emulate_string_inst(struct pt_regs *regs, u32 instword)
 {
 	u8 rT = (instword >> 21) & 0x1f;
@@ -707,6 +710,23 @@ static int emulate_popcntb_inst(struct pt_regs *regs, u32 instword)
 	return 0;
 }

+static int emulate_isel(struct pt_regs *regs, u32 instword)
+{
+	u8 rT = (instword >> 21) & 0x1f;
+	u8 rA = (instword >> 16) & 0x1f;
+	u8 rB = (instword >> 11) & 0x1f;
+	u8 BC = (instword >> 6) & 0x1f;
+	u8 bit;
+	unsigned long tmp;
+
+	tmp = (rA == 0) ? 0 : regs->gpr[rA];
+	bit = (regs->ccr >> (31 - BC)) & 0x1;
+
+	regs->gpr[rT] = bit ? tmp : regs->gpr[rB];
+
+	return 0;
+}
+
 static int emulate_instruction(struct pt_regs *regs)
 {
 	u32 instword;
@@ -749,6 +769,11 @@ static int emulate_instruction(struct pt_regs *regs)
 		return emulate_popcntb_inst(regs, instword);
 	}

+	/* Emulate isel (Integer Select) instruction */
+	if ((instword & INST_ISEL_MASK) == INST_ISEL) {
+		return emulate_isel(regs, instword);
+	}
+
 	return -EINVAL;
 }

-- 
1.5.3.4