Re: [PATCH] powerpc: emulate power5 popcntb instruction
From: Willschm <hidden>
Date: 2006-08-28 18:03:54
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
On Thu, 2006-24-08 at 16:36 +1000, Paul Mackerras wrote:
Will Schmidt writes: I just did a patch to fix the existing masks. Could you do a new version of this patch that doesn't include the unrelated mask fixes please? Also it would be really nice if you could figure out a way to avoid doing the unnecessary 64-bit logical operations on 32-bit machines - i.e. using an unsigned long for tmp, but then the constants become problematic. Maybe you need something like #define LCONST(x) ((unsigned long)(x##ULL))
Ok, how about this.. In an attempt to make it easier for a power5 optimized app to run on a power4 or a 970 or random earlier machine, this provides emulation of the popcntb instruction. Signed-off-by: Will Schmidt <redacted> ---
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 2105767..f85a3af 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c@@ -588,6 +588,9 @@ #define INST_LSWX 0x7c00042a #define INST_STSWI 0x7c0005aa #define INST_STSWX 0x7c00052a +#define INST_POPCNTB 0x7c0000f4 +#define INST_POPCNTB_MASK 0xfc0007fe + static int emulate_string_inst(struct pt_regs *regs, u32 instword) { u8 rT = (instword >> 21) & 0x1f;
@@ -656,6 +659,25 @@ static int emulate_string_inst(struct pt return 0; } +#define LCONST(x) ((unsigned long)(x##ULL)) + +static int emulate_popcntb_inst(struct pt_regs *regs, u32 instword) +{ + u32 ra,rs; + u64 tmp; + + ra = (instword >> 16) & 0x1f; + rs = (instword >> 21) & 0x1f; + + tmp = regs->gpr[rs]; + tmp = tmp - ((tmp >> 1) & LCONST(0x5555555555555555)); + tmp = (tmp & LCONST(0x3333333333333333)) + ((tmp >> 2) & LCONST(0x3333333333333333)); + tmp = (tmp + (tmp >> 4)) & LCONST(0x0f0f0f0f0f0f0f0f); + regs->gpr[ra] = tmp; + + return 0; +} + static int emulate_instruction(struct pt_regs *regs) { u32 instword;
@@ -693,6 +715,11 @@ static int emulate_instruction(struct pt if ((instword & INST_STRING_GEN_MASK) == INST_STRING) return emulate_string_inst(regs, instword); + /* Emulate the popcntb (Population Count Bytes) instruction. */ + if ((instword & INST_POPCNTB_MASK) == INST_POPCNTB) { + return emulate_popcntb_inst(regs, instword); + } + return -EINVAL; }