powerpc/lib/sstep: Add popcnt instruction emulation

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.dev@gmail.com>
Reviewed-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index cc6327b..d172de3 100644 (file)
--- 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;
@@ -1209,6 +1237,10 @@ 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;
@@ -1221,6 +1253,10 @@ 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;
@@ -1232,7 +1268,11 @@ 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;