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From: | Richard Henderson |
Subject: | Re: [PATCH 07/33] target/ppc: Implement cntlzdm |
Date: | Fri, 22 Oct 2021 16:16:10 -0700 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 |
On 10/21/21 12:45 PM, matheus.ferst@eldorado.org.br wrote:
+uint64_t helper_CNTLZDM(uint64_t src, uint64_t mask) +{ + uint64_t sel_bit, count = 0; + + while (mask != 0) { + sel_bit = 0x8000000000000000ULL >> clz64(mask); + + if (src & sel_bit) { + break; + }
We need to count how many mask are set left of mask & src. How about sh = clz64(src & mask); if (sh == 0) { return 0; } return ctpop64(mask >> (64 - sh)); which could probably be implemented inline relatively easy.
+static bool trans_CNTLZDM(DisasContext *ctx, arg_X *a) +{ + REQUIRE_64BIT(ctx); + REQUIRE_INSNS_FLAGS2(ctx, ISA310); +#if defined(TARGET_PPC64) + gen_helper_CNTLZDM(cpu_gpr[a->ra], cpu_gpr[a->rt], cpu_gpr[a->rb]); +#else + qemu_build_not_reached(); +#endif + return true; +}
Why the ifdef here? Oh, I see. You could just use target_long in the helper to avoid that. And if not, you should move the helper into an ifdef too.
r~
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