From 0ef3814fe1b5579890a7758e6e52d12b8a96fdf2 Mon Sep 17 00:00:00 2001 From: Han Shen Date: Mon, 20 Jul 2015 13:04:06 -0700 Subject: Optimize erratum 843419 fix. gold/ChangeLog: * aarch64.cc (AArch64_insn_utilities::is_adr): New method. (AArch64_insn_utilities::aarch64_adr_encode_imm): New method. (AArch64_insn_utilities::aarch64_adrp_decode_imm): New method. (E843419_stub): New sub-class of Erratum_stub. (AArch64_relobj::try_fix_erratum_843419_optimized): New method. (AArch64_relobj::section_needs_reloc_stub_scanning): Try optimized fix. (AArch64_relobj::create_erratum_stub): Add 1 argument. (Target_aarch64::scan_erratum_843419_span): Pass in adrp insn offset. --- gold/aarch64.cc | 165 +++++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 153 insertions(+), 12 deletions(-) (limited to 'gold/aarch64.cc') diff --git a/gold/aarch64.cc b/gold/aarch64.cc index bc86f68a9f1..4153389643e 100644 --- a/gold/aarch64.cc +++ b/gold/aarch64.cc @@ -102,6 +102,10 @@ public: aarch64_ra(Insntype insn) { return aarch64_bits(insn, 10, 5); } + static bool + is_adr(const Insntype insn) + { return (insn & 0x9F000000) == 0x10000000; } + static bool is_adrp(const Insntype insn) { return (insn & 0x9F000000) == 0x90000000; } @@ -126,6 +130,39 @@ public: aarch64_rt2(const Insntype insn) { return aarch64_bits(insn, 10, 5); } + // Encode imm21 into adr. Signed imm21 is in the range of [-1M, 1M). + static Insntype + aarch64_adr_encode_imm(Insntype adr, int imm21) + { + gold_assert(is_adr(adr)); + gold_assert(-(1 << 20) <= imm21 && imm21 < (1 << 20)); + const int mask19 = (1 << 19) - 1; + const int mask2 = 3; + adr &= ~((mask19 << 5) | (mask2 << 29)); + adr |= ((imm21 & mask2) << 29) | (((imm21 >> 2) & mask19) << 5); + return adr; + } + + // Retrieve encoded adrp 33-bit signed imm value. This value is obtained by + // 21-bit signed imm encoded in the insn multiplied by 4k (page size) and + // 64-bit sign-extended, resulting in [-4G, 4G) with 12-lsb being 0. + static int64_t + aarch64_adrp_decode_imm(const Insntype adrp) + { + const int mask19 = (1 << 19) - 1; + const int mask2 = 3; + gold_assert(is_adrp(adrp)); + // 21-bit imm encoded in adrp. + uint64_t imm = ((adrp >> 29) & mask2) | (((adrp >> 5) & mask19) << 2); + // Retrieve msb of 21-bit-signed imm for sign extension. + uint64_t msbt = (imm >> 20) & 1; + // Real value is imm multipled by 4k. Value now has 33-bit information. + int64_t value = imm << 12; + // Sign extend to 64-bit by repeating msbt 31 (64-33) times and merge it + // with value. + return ((((uint64_t)(1) << 32) - msbt) << 33) | value; + } + static bool aarch64_b(const Insntype insn) { return (insn & 0xFC000000) == 0x14000000; } @@ -1019,6 +1056,35 @@ private: AArch64_address erratum_address_; }; // End of "Erratum_stub". + +// Erratum sub class to wrap additional info needed by 843419. In fixing this +// erratum, we may choose to replace 'adrp' with 'adr', in this case, we need +// adrp's code position (two or three insns before erratum insn itself). + +template +class E843419_stub : public Erratum_stub +{ +public: + typedef typename AArch64_insn_utilities::Insntype Insntype; + + E843419_stub(AArch64_relobj* relobj, + unsigned int shndx, unsigned int sh_offset, + unsigned int adrp_sh_offset) + : Erratum_stub(relobj, ST_E_843419, shndx, sh_offset), + adrp_sh_offset_(adrp_sh_offset) + {} + + unsigned int + adrp_sh_offset() const + { return this->adrp_sh_offset_; } + +private: + // Section offset of "adrp". (We do not need a "adrp_shndx_" field, because we + // can can obtain it from its parent.) + const unsigned int adrp_sh_offset_; +}; + + template const int Erratum_stub::STUB_ADDR_ALIGN = 4; @@ -1754,6 +1820,13 @@ class AArch64_relobj : public Sized_relobj_file void fix_errata(typename Sized_relobj_file::Views* pviews); + // Try to fix erratum 843419 in an optimized way. Return true if patch is + // applied. + bool + try_fix_erratum_843419_optimized( + The_erratum_stub*, + typename Sized_relobj_file::View_size&); + // Whether a section needs to be scanned for relocation stubs. bool section_needs_reloc_stub_scanning(const elfcpp::Shdr&, @@ -1891,18 +1964,75 @@ AArch64_relobj::fix_errata( Insntype insn_to_fix = ip[0]; stub->update_erratum_insn(insn_to_fix); - // Replace the erratum insn with a branch-to-stub. - AArch64_address stub_address = - stub_table->erratum_stub_address(stub); - unsigned int b_offset = stub_address - stub->erratum_address(); - AArch64_relocate_functions::construct_b( - pview.view + stub->sh_offset(), b_offset & 0xfffffff); + // First try to see if erratum is 843419 and if it can be fixed + // without using branch-to-stub. + if (!try_fix_erratum_843419_optimized(stub, pview)) + { + // Replace the erratum insn with a branch-to-stub. + AArch64_address stub_address = + stub_table->erratum_stub_address(stub); + unsigned int b_offset = stub_address - stub->erratum_address(); + AArch64_relocate_functions::construct_b( + pview.view + stub->sh_offset(), b_offset & 0xfffffff); + } ++p; } } } +// This is an optimization for 843419. This erratum requires the sequence begin +// with 'adrp', when final value calculated by adrp fits in adr, we can just +// replace 'adrp' with 'adr', so we save 2 jumps per occurrence. (Note, however, +// in this case, we do not delete the erratum stub (too late to do so), it is +// merely generated without ever being called.) + +template +bool +AArch64_relobj::try_fix_erratum_843419_optimized( + The_erratum_stub* stub, + typename Sized_relobj_file::View_size& pview) +{ + if (stub->type() != ST_E_843419) + return false; + + typedef AArch64_insn_utilities Insn_utilities; + typedef typename elfcpp::Swap<32,big_endian>::Valtype Insntype; + E843419_stub* e843419_stub = + reinterpret_cast*>(stub); + AArch64_address pc = pview.address + e843419_stub->adrp_sh_offset(); + Insntype* adrp_view = reinterpret_cast( + pview.view + e843419_stub->adrp_sh_offset()); + Insntype adrp_insn = adrp_view[0]; + gold_assert(Insn_utilities::is_adrp(adrp_insn)); + // Get adrp 33-bit signed imm value. + int64_t adrp_imm = Insn_utilities:: + aarch64_adrp_decode_imm(adrp_insn); + // adrp - final value transferred to target register is calculated as: + // PC[11:0] = Zeros(12) + // adrp_dest_value = PC + adrp_imm; + int64_t adrp_dest_value = (pc & ~((1 << 12) - 1)) + adrp_imm; + // adr -final value transferred to target register is calucalted as: + // PC + adr_imm + // So we have: + // PC + adr_imm = adrp_dest_value + // ==> + // adr_imm = adrp_dest_value - PC + int64_t adr_imm = adrp_dest_value - pc; + // Check if imm fits in adr (21-bit signed). + if (-(1 << 20) <= adr_imm && adr_imm < (1 << 20)) + { + // Convert 'adrp' into 'adr'. + Insntype adr_insn = adrp_insn & ((1 << 31) - 1); + adr_insn = Insn_utilities:: + aarch64_adr_encode_imm(adr_insn, adr_imm); + elfcpp::Swap<32, big_endian>::writeval(adrp_view, adr_insn); + return true; + } + return false; +} + + // Relocate sections. template @@ -3166,14 +3296,16 @@ class Target_aarch64 : public Sized_target return this->plt_; } - // Helper method to create erratum stubs for ST_E_843419 and ST_E_835769. + // Helper method to create erratum stubs for ST_E_843419 and ST_E_835769. For + // ST_E_843419, we need an additional field for adrp offset. void create_erratum_stub( AArch64_relobj* relobj, unsigned int shndx, section_size_type erratum_insn_offset, Address erratum_address, typename Insn_utilities::Insntype erratum_insn, - int erratum_type); + int erratum_type, + unsigned int e843419_adrp_offset=0); // Return whether this is a 3-insn erratum sequence. bool is_erratum_843419_sequence( @@ -7871,7 +8003,8 @@ Target_aarch64::create_erratum_stub( section_size_type erratum_insn_offset, Address erratum_address, typename Insn_utilities::Insntype erratum_insn, - int erratum_type) + int erratum_type, + unsigned int e843419_adrp_offset) { gold_assert(erratum_type == ST_E_843419 || erratum_type == ST_E_835769); The_stub_table* stub_table = relobj->stub_table(shndx); @@ -7881,8 +8014,15 @@ Target_aarch64::create_erratum_stub( erratum_insn_offset) == NULL) { const int BPI = AArch64_insn_utilities::BYTES_PER_INSN; - The_erratum_stub* stub = new The_erratum_stub( - relobj, erratum_type, shndx, erratum_insn_offset); + The_erratum_stub* stub; + if (erratum_type == ST_E_835769) + stub = new The_erratum_stub(relobj, erratum_type, shndx, + erratum_insn_offset); + else if (erratum_type == ST_E_843419) + stub = new E843419_stub( + relobj, shndx, erratum_insn_offset, e843419_adrp_offset); + else + gold_unreachable(); stub->set_erratum_insn(erratum_insn); stub->set_erratum_address(erratum_address); // For erratum ST_E_843419 and ST_E_835769, the destination address is @@ -8027,7 +8167,8 @@ Target_aarch64::scan_erratum_843419_span( output_address + offset + insn_offset; create_erratum_stub(relobj, shndx, erratum_insn_offset, erratum_address, - erratum_insn, ST_E_843419); + erratum_insn, ST_E_843419, + span_start + offset); } } -- cgit v1.2.1