From 46b8b3d6f87c0c65d908e3f6c83532d7286868b9 Mon Sep 17 00:00:00 2001 From: Andrew Burgess Date: Mon, 21 Jun 2021 15:10:14 +0100 Subject: [PATCH] opcodes: make use of __builtin_popcount when available This commit provides a small performance improvement when starting up CGEN based disassemblers by making use of __builtin_popcount. The #if check used in this commit was copied from bfd/elf32-arm.c where __builtin_popcount is also used. I ran into this code while investigating some GDB tests that would occasionally timeout. One of the reason these tests were having problems is that the m16c and m32c disassemblers take so long to initialise themselves. Speeding up count_decodable_bits helps, but is not a total solution. Still, this felt like an easy win which added minimal extra complexity, so I figure its worth doing. opcodes/ChangeLog: * cgen-dis.c (count_decodable_bits): Use __builtin_popcount when available. --- opcodes/ChangeLog | 5 +++++ opcodes/cgen-dis.c | 4 ++++ 2 files changed, 9 insertions(+) diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog index 0dab08e6e54..20e0524a1bf 100644 --- a/opcodes/ChangeLog +++ b/opcodes/ChangeLog @@ -1,3 +1,8 @@ +2021-06-22 Andrew Burgess + + * cgen-dis.c (count_decodable_bits): Use __builtin_popcount when + available. + 2021-06-22 Alan Modra * pj-dis.c (print_insn_pj): Don't print trailing tab. Do diff --git a/opcodes/cgen-dis.c b/opcodes/cgen-dis.c index 6a93060edd5..1a5d1ae8459 100644 --- a/opcodes/cgen-dis.c +++ b/opcodes/cgen-dis.c @@ -40,6 +40,9 @@ static int count_decodable_bits (const CGEN_INSN *insn) { unsigned mask = CGEN_INSN_BASE_MASK (insn); +#if GCC_VERSION >= 3004 + return __builtin_popcount (mask); +#else int bits = 0; unsigned m; @@ -49,6 +52,7 @@ count_decodable_bits (const CGEN_INSN *insn) ++bits; } return bits; +#endif } /* Add an instruction to the hash chain. */ -- 2.30.2