This adds emulations for the popcntb, popcntw, and popcntd instructions.
Tested for correctness against the popcnt{b,w,d} instructions on ppc64le.
Signed-off-by: Matt Brown <matthew.brown....@gmail.com>
---
v4:
- change ifdef macro from __powerpc64__ to CONFIG_PPC64
- slight optimisations
(now identical to the popcntb implementation in kernel/traps.c)
v3:
- optimised using the Giles-Miller method of side-ways addition
v2:
- fixed opcodes
- fixed typecasting
- fixed bitshifting error for both 32 and 64bit arch
---
arch/powerpc/lib/sstep.c | 42 +++++++++++++++++++++++++++++++++++++++++-
1 file changed, 41 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index 87d277f..2fd7377 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -612,6 +612,34 @@ static nokprobe_inline void do_cmpb(struct pt_regs *regs,
unsigned long v1,
regs->gpr[rd] = out_val;
}
+/*
+ * The size parameter is used to adjust the equivalent popcnt instruction.
+ * popcntb = 8, popcntw = 32, popcntd = 64
+ */
+static nokprobe_inline void do_popcnt(struct pt_regs *regs, unsigned long v1,
+ int size, int ra)
+{
+ unsigned long long out = v1;
+
+ out -= (out >> 1) & 0x5555555555555555;
+ out = (0x3333333333333333 & out) + (0x3333333333333333 & (out >> 2));
+ out = (out + (out >> 4)) & 0x0f0f0f0f0f0f0f0f;
+
+ if (size == 8) { /* popcntb */
+ regs->gpr[ra] = out;
+ return;
+ }
+ out += out >> 8;
+ out += out >> 16;
+ if (size == 32) { /* popcntw */
+ regs->gpr[ra] = out & 0x0000003f0000003f;
+ return;
+ }
+
+ out = (out + (out >> 32)) & 0x7f;
+ regs->gpr[ra] = out; /* popcntd */
+}
+
static nokprobe_inline int trap_compare(long v1, long v2)
{
int ret = 0;
@@ -1194,6 +1222,10 @@ int analyse_instr(struct instruction_op *op, struct
pt_regs *regs,
regs->gpr[ra] = regs->gpr[rd] & ~regs->gpr[rb];
goto logical_done;
+ case 122: /* popcntb */
+ do_popcnt(regs, regs->gpr[rd], 8, ra);
+ goto logical_done;
+
case 124: /* nor */
regs->gpr[ra] = ~(regs->gpr[rd] | regs->gpr[rb]);
goto logical_done;
@@ -1206,6 +1238,10 @@ int analyse_instr(struct instruction_op *op, struct
pt_regs *regs,
regs->gpr[ra] = regs->gpr[rd] ^ regs->gpr[rb];
goto logical_done;
+ case 378: /* popcntw */
+ do_popcnt(regs, regs->gpr[rd], 32, ra);
+ goto logical_done;
+
case 412: /* orc */
regs->gpr[ra] = regs->gpr[rd] | ~regs->gpr[rb];
goto logical_done;
@@ -1217,7 +1253,11 @@ int analyse_instr(struct instruction_op *op, struct
pt_regs *regs,
case 476: /* nand */
regs->gpr[ra] = ~(regs->gpr[rd] & regs->gpr[rb]);
goto logical_done;
-
+#ifdef CONFIG_PPC64
+ case 506: /* popcntd */
+ do_popcnt(regs, regs->gpr[rd], 64, ra);
+ goto logical_done;
+#endif
case 922: /* extsh */
regs->gpr[ra] = (signed short) regs->gpr[rd];
goto logical_done;
--
2.9.3
