--- /dev/null
+diff -urN llvm-12.0.0.src.orig/tools/lld/MachO/mach-o/compact_unwind_encoding.h llvm-12.0.0.src/tools/lld/MachO/mach-o/compact_unwind_encoding.h
+--- llvm-12.0.0.src.orig/tools/lld/MachO/mach-o/compact_unwind_encoding.h 1970-01-01 01:00:00.000000000 +0100
++++ llvm-12.0.0.src/tools/lld/MachO/mach-o/compact_unwind_encoding.h 2021-04-16 16:24:55.701577683 +0200
+@@ -0,0 +1,477 @@
++//===------------------ mach-o/compact_unwind_encoding.h ------------------===//
++//
++// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
++// See https://llvm.org/LICENSE.txt for license information.
++// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
++//
++//
++// Darwin's alternative to DWARF based unwind encodings.
++//
++//===----------------------------------------------------------------------===//
++
++
++#ifndef __COMPACT_UNWIND_ENCODING__
++#define __COMPACT_UNWIND_ENCODING__
++
++#include <stdint.h>
++
++//
++// Compilers can emit standard DWARF FDEs in the __TEXT,__eh_frame section
++// of object files. Or compilers can emit compact unwind information in
++// the __LD,__compact_unwind section.
++//
++// When the linker creates a final linked image, it will create a
++// __TEXT,__unwind_info section. This section is a small and fast way for the
++// runtime to access unwind info for any given function. If the compiler
++// emitted compact unwind info for the function, that compact unwind info will
++// be encoded in the __TEXT,__unwind_info section. If the compiler emitted
++// DWARF unwind info, the __TEXT,__unwind_info section will contain the offset
++// of the FDE in the __TEXT,__eh_frame section in the final linked image.
++//
++// Note: Previously, the linker would transform some DWARF unwind infos into
++// compact unwind info. But that is fragile and no longer done.
++
++
++//
++// The compact unwind endoding is a 32-bit value which encoded in an
++// architecture specific way, which registers to restore from where, and how
++// to unwind out of the function.
++//
++typedef uint32_t compact_unwind_encoding_t;
++
++
++// architecture independent bits
++enum {
++ UNWIND_IS_NOT_FUNCTION_START = 0x80000000,
++ UNWIND_HAS_LSDA = 0x40000000,
++ UNWIND_PERSONALITY_MASK = 0x30000000,
++};
++
++
++
++
++//
++// x86
++//
++// 1-bit: start
++// 1-bit: has lsda
++// 2-bit: personality index
++//
++// 4-bits: 0=old, 1=ebp based, 2=stack-imm, 3=stack-ind, 4=DWARF
++// ebp based:
++// 15-bits (5*3-bits per reg) register permutation
++// 8-bits for stack offset
++// frameless:
++// 8-bits stack size
++// 3-bits stack adjust
++// 3-bits register count
++// 10-bits register permutation
++//
++enum {
++ UNWIND_X86_MODE_MASK = 0x0F000000,
++ UNWIND_X86_MODE_EBP_FRAME = 0x01000000,
++ UNWIND_X86_MODE_STACK_IMMD = 0x02000000,
++ UNWIND_X86_MODE_STACK_IND = 0x03000000,
++ UNWIND_X86_MODE_DWARF = 0x04000000,
++
++ UNWIND_X86_EBP_FRAME_REGISTERS = 0x00007FFF,
++ UNWIND_X86_EBP_FRAME_OFFSET = 0x00FF0000,
++
++ UNWIND_X86_FRAMELESS_STACK_SIZE = 0x00FF0000,
++ UNWIND_X86_FRAMELESS_STACK_ADJUST = 0x0000E000,
++ UNWIND_X86_FRAMELESS_STACK_REG_COUNT = 0x00001C00,
++ UNWIND_X86_FRAMELESS_STACK_REG_PERMUTATION = 0x000003FF,
++
++ UNWIND_X86_DWARF_SECTION_OFFSET = 0x00FFFFFF,
++};
++
++enum {
++ UNWIND_X86_REG_NONE = 0,
++ UNWIND_X86_REG_EBX = 1,
++ UNWIND_X86_REG_ECX = 2,
++ UNWIND_X86_REG_EDX = 3,
++ UNWIND_X86_REG_EDI = 4,
++ UNWIND_X86_REG_ESI = 5,
++ UNWIND_X86_REG_EBP = 6,
++};
++
++//
++// For x86 there are four modes for the compact unwind encoding:
++// UNWIND_X86_MODE_EBP_FRAME:
++// EBP based frame where EBP is push on stack immediately after return address,
++// then ESP is moved to EBP. Thus, to unwind ESP is restored with the current
++// EPB value, then EBP is restored by popping off the stack, and the return
++// is done by popping the stack once more into the pc.
++// All non-volatile registers that need to be restored must have been saved
++// in a small range in the stack that starts EBP-4 to EBP-1020. The offset/4
++// is encoded in the UNWIND_X86_EBP_FRAME_OFFSET bits. The registers saved
++// are encoded in the UNWIND_X86_EBP_FRAME_REGISTERS bits as five 3-bit entries.
++// Each entry contains which register to restore.
++// UNWIND_X86_MODE_STACK_IMMD:
++// A "frameless" (EBP not used as frame pointer) function with a small
++// constant stack size. To return, a constant (encoded in the compact
++// unwind encoding) is added to the ESP. Then the return is done by
++// popping the stack into the pc.
++// All non-volatile registers that need to be restored must have been saved
++// on the stack immediately after the return address. The stack_size/4 is
++// encoded in the UNWIND_X86_FRAMELESS_STACK_SIZE (max stack size is 1024).
++// The number of registers saved is encoded in UNWIND_X86_FRAMELESS_STACK_REG_COUNT.
++// UNWIND_X86_FRAMELESS_STACK_REG_PERMUTATION constains which registers were
++// saved and their order.
++// UNWIND_X86_MODE_STACK_IND:
++// A "frameless" (EBP not used as frame pointer) function large constant
++// stack size. This case is like the previous, except the stack size is too
++// large to encode in the compact unwind encoding. Instead it requires that
++// the function contains "subl $nnnnnnnn,ESP" in its prolog. The compact
++// encoding contains the offset to the nnnnnnnn value in the function in
++// UNWIND_X86_FRAMELESS_STACK_SIZE.
++// UNWIND_X86_MODE_DWARF:
++// No compact unwind encoding is available. Instead the low 24-bits of the
++// compact encoding is the offset of the DWARF FDE in the __eh_frame section.
++// This mode is never used in object files. It is only generated by the
++// linker in final linked images which have only DWARF unwind info for a
++// function.
++//
++// The permutation encoding is a Lehmer code sequence encoded into a
++// single variable-base number so we can encode the ordering of up to
++// six registers in a 10-bit space.
++//
++// The following is the algorithm used to create the permutation encoding used
++// with frameless stacks. It is passed the number of registers to be saved and
++// an array of the register numbers saved.
++//
++//uint32_t permute_encode(uint32_t registerCount, const uint32_t registers[6])
++//{
++// uint32_t renumregs[6];
++// for (int i=6-registerCount; i < 6; ++i) {
++// int countless = 0;
++// for (int j=6-registerCount; j < i; ++j) {
++// if ( registers[j] < registers[i] )
++// ++countless;
++// }
++// renumregs[i] = registers[i] - countless -1;
++// }
++// uint32_t permutationEncoding = 0;
++// switch ( registerCount ) {
++// case 6:
++// permutationEncoding |= (120*renumregs[0] + 24*renumregs[1]
++// + 6*renumregs[2] + 2*renumregs[3]
++// + renumregs[4]);
++// break;
++// case 5:
++// permutationEncoding |= (120*renumregs[1] + 24*renumregs[2]
++// + 6*renumregs[3] + 2*renumregs[4]
++// + renumregs[5]);
++// break;
++// case 4:
++// permutationEncoding |= (60*renumregs[2] + 12*renumregs[3]
++// + 3*renumregs[4] + renumregs[5]);
++// break;
++// case 3:
++// permutationEncoding |= (20*renumregs[3] + 4*renumregs[4]
++// + renumregs[5]);
++// break;
++// case 2:
++// permutationEncoding |= (5*renumregs[4] + renumregs[5]);
++// break;
++// case 1:
++// permutationEncoding |= (renumregs[5]);
++// break;
++// }
++// return permutationEncoding;
++//}
++//
++
++
++
++
++//
++// x86_64
++//
++// 1-bit: start
++// 1-bit: has lsda
++// 2-bit: personality index
++//
++// 4-bits: 0=old, 1=rbp based, 2=stack-imm, 3=stack-ind, 4=DWARF
++// rbp based:
++// 15-bits (5*3-bits per reg) register permutation
++// 8-bits for stack offset
++// frameless:
++// 8-bits stack size
++// 3-bits stack adjust
++// 3-bits register count
++// 10-bits register permutation
++//
++enum {
++ UNWIND_X86_64_MODE_MASK = 0x0F000000,
++ UNWIND_X86_64_MODE_RBP_FRAME = 0x01000000,
++ UNWIND_X86_64_MODE_STACK_IMMD = 0x02000000,
++ UNWIND_X86_64_MODE_STACK_IND = 0x03000000,
++ UNWIND_X86_64_MODE_DWARF = 0x04000000,
++
++ UNWIND_X86_64_RBP_FRAME_REGISTERS = 0x00007FFF,
++ UNWIND_X86_64_RBP_FRAME_OFFSET = 0x00FF0000,
++
++ UNWIND_X86_64_FRAMELESS_STACK_SIZE = 0x00FF0000,
++ UNWIND_X86_64_FRAMELESS_STACK_ADJUST = 0x0000E000,
++ UNWIND_X86_64_FRAMELESS_STACK_REG_COUNT = 0x00001C00,
++ UNWIND_X86_64_FRAMELESS_STACK_REG_PERMUTATION = 0x000003FF,
++
++ UNWIND_X86_64_DWARF_SECTION_OFFSET = 0x00FFFFFF,
++};
++
++enum {
++ UNWIND_X86_64_REG_NONE = 0,
++ UNWIND_X86_64_REG_RBX = 1,
++ UNWIND_X86_64_REG_R12 = 2,
++ UNWIND_X86_64_REG_R13 = 3,
++ UNWIND_X86_64_REG_R14 = 4,
++ UNWIND_X86_64_REG_R15 = 5,
++ UNWIND_X86_64_REG_RBP = 6,
++};
++//
++// For x86_64 there are four modes for the compact unwind encoding:
++// UNWIND_X86_64_MODE_RBP_FRAME:
++// RBP based frame where RBP is push on stack immediately after return address,
++// then RSP is moved to RBP. Thus, to unwind RSP is restored with the current
++// EPB value, then RBP is restored by popping off the stack, and the return
++// is done by popping the stack once more into the pc.
++// All non-volatile registers that need to be restored must have been saved
++// in a small range in the stack that starts RBP-8 to RBP-2040. The offset/8
++// is encoded in the UNWIND_X86_64_RBP_FRAME_OFFSET bits. The registers saved
++// are encoded in the UNWIND_X86_64_RBP_FRAME_REGISTERS bits as five 3-bit entries.
++// Each entry contains which register to restore.
++// UNWIND_X86_64_MODE_STACK_IMMD:
++// A "frameless" (RBP not used as frame pointer) function with a small
++// constant stack size. To return, a constant (encoded in the compact
++// unwind encoding) is added to the RSP. Then the return is done by
++// popping the stack into the pc.
++// All non-volatile registers that need to be restored must have been saved
++// on the stack immediately after the return address. The stack_size/8 is
++// encoded in the UNWIND_X86_64_FRAMELESS_STACK_SIZE (max stack size is 2048).
++// The number of registers saved is encoded in UNWIND_X86_64_FRAMELESS_STACK_REG_COUNT.
++// UNWIND_X86_64_FRAMELESS_STACK_REG_PERMUTATION constains which registers were
++// saved and their order.
++// UNWIND_X86_64_MODE_STACK_IND:
++// A "frameless" (RBP not used as frame pointer) function large constant
++// stack size. This case is like the previous, except the stack size is too
++// large to encode in the compact unwind encoding. Instead it requires that
++// the function contains "subq $nnnnnnnn,RSP" in its prolog. The compact
++// encoding contains the offset to the nnnnnnnn value in the function in
++// UNWIND_X86_64_FRAMELESS_STACK_SIZE.
++// UNWIND_X86_64_MODE_DWARF:
++// No compact unwind encoding is available. Instead the low 24-bits of the
++// compact encoding is the offset of the DWARF FDE in the __eh_frame section.
++// This mode is never used in object files. It is only generated by the
++// linker in final linked images which have only DWARF unwind info for a
++// function.
++//
++
++
++// ARM64
++//
++// 1-bit: start
++// 1-bit: has lsda
++// 2-bit: personality index
++//
++// 4-bits: 4=frame-based, 3=DWARF, 2=frameless
++// frameless:
++// 12-bits of stack size
++// frame-based:
++// 4-bits D reg pairs saved
++// 5-bits X reg pairs saved
++// DWARF:
++// 24-bits offset of DWARF FDE in __eh_frame section
++//
++enum {
++ UNWIND_ARM64_MODE_MASK = 0x0F000000,
++ UNWIND_ARM64_MODE_FRAMELESS = 0x02000000,
++ UNWIND_ARM64_MODE_DWARF = 0x03000000,
++ UNWIND_ARM64_MODE_FRAME = 0x04000000,
++
++ UNWIND_ARM64_FRAME_X19_X20_PAIR = 0x00000001,
++ UNWIND_ARM64_FRAME_X21_X22_PAIR = 0x00000002,
++ UNWIND_ARM64_FRAME_X23_X24_PAIR = 0x00000004,
++ UNWIND_ARM64_FRAME_X25_X26_PAIR = 0x00000008,
++ UNWIND_ARM64_FRAME_X27_X28_PAIR = 0x00000010,
++ UNWIND_ARM64_FRAME_D8_D9_PAIR = 0x00000100,
++ UNWIND_ARM64_FRAME_D10_D11_PAIR = 0x00000200,
++ UNWIND_ARM64_FRAME_D12_D13_PAIR = 0x00000400,
++ UNWIND_ARM64_FRAME_D14_D15_PAIR = 0x00000800,
++
++ UNWIND_ARM64_FRAMELESS_STACK_SIZE_MASK = 0x00FFF000,
++ UNWIND_ARM64_DWARF_SECTION_OFFSET = 0x00FFFFFF,
++};
++// For arm64 there are three modes for the compact unwind encoding:
++// UNWIND_ARM64_MODE_FRAME:
++// This is a standard arm64 prolog where FP/LR are immediately pushed on the
++// stack, then SP is copied to FP. If there are any non-volatile registers
++// saved, then are copied into the stack frame in pairs in a contiguous
++// range right below the saved FP/LR pair. Any subset of the five X pairs
++// and four D pairs can be saved, but the memory layout must be in register
++// number order.
++// UNWIND_ARM64_MODE_FRAMELESS:
++// A "frameless" leaf function, where FP/LR are not saved. The return address
++// remains in LR throughout the function. If any non-volatile registers
++// are saved, they must be pushed onto the stack before any stack space is
++// allocated for local variables. The stack sized (including any saved
++// non-volatile registers) divided by 16 is encoded in the bits
++// UNWIND_ARM64_FRAMELESS_STACK_SIZE_MASK.
++// UNWIND_ARM64_MODE_DWARF:
++// No compact unwind encoding is available. Instead the low 24-bits of the
++// compact encoding is the offset of the DWARF FDE in the __eh_frame section.
++// This mode is never used in object files. It is only generated by the
++// linker in final linked images which have only DWARF unwind info for a
++// function.
++//
++
++
++
++
++
++////////////////////////////////////////////////////////////////////////////////
++//
++// Relocatable Object Files: __LD,__compact_unwind
++//
++////////////////////////////////////////////////////////////////////////////////
++
++//
++// A compiler can generated compact unwind information for a function by adding
++// a "row" to the __LD,__compact_unwind section. This section has the
++// S_ATTR_DEBUG bit set, so the section will be ignored by older linkers.
++// It is removed by the new linker, so never ends up in final executables.
++// This section is a table, initially with one row per function (that needs
++// unwind info). The table columns and some conceptual entries are:
++//
++// range-start pointer to start of function/range
++// range-length
++// compact-unwind-encoding 32-bit encoding
++// personality-function or zero if no personality function
++// lsda or zero if no LSDA data
++//
++// The length and encoding fields are 32-bits. The other are all pointer sized.
++//
++// In x86_64 assembly, these entry would look like:
++//
++// .section __LD,__compact_unwind,regular,debug
++//
++// #compact unwind for _foo
++// .quad _foo
++// .set L1,LfooEnd-_foo
++// .long L1
++// .long 0x01010001
++// .quad 0
++// .quad 0
++//
++// #compact unwind for _bar
++// .quad _bar
++// .set L2,LbarEnd-_bar
++// .long L2
++// .long 0x01020011
++// .quad __gxx_personality
++// .quad except_tab1
++//
++//
++// Notes: There is no need for any labels in the the __compact_unwind section.
++// The use of the .set directive is to force the evaluation of the
++// range-length at assembly time, instead of generating relocations.
++//
++// To support future compiler optimizations where which non-volatile registers
++// are saved changes within a function (e.g. delay saving non-volatiles until
++// necessary), there can by multiple lines in the __compact_unwind table for one
++// function, each with a different (non-overlapping) range and each with
++// different compact unwind encodings that correspond to the non-volatiles
++// saved at that range of the function.
++//
++// If a particular function is so wacky that there is no compact unwind way
++// to encode it, then the compiler can emit traditional DWARF unwind info.
++// The runtime will use which ever is available.
++//
++// Runtime support for compact unwind encodings are only available on 10.6
++// and later. So, the compiler should not generate it when targeting pre-10.6.
++
++
++
++
++////////////////////////////////////////////////////////////////////////////////
++//
++// Final Linked Images: __TEXT,__unwind_info
++//
++////////////////////////////////////////////////////////////////////////////////
++
++//
++// The __TEXT,__unwind_info section is laid out for an efficient two level lookup.
++// The header of the section contains a coarse index that maps function address
++// to the page (4096 byte block) containing the unwind info for that function.
++//
++
++#define UNWIND_SECTION_VERSION 1
++struct unwind_info_section_header
++{
++ uint32_t version; // UNWIND_SECTION_VERSION
++ uint32_t commonEncodingsArraySectionOffset;
++ uint32_t commonEncodingsArrayCount;
++ uint32_t personalityArraySectionOffset;
++ uint32_t personalityArrayCount;
++ uint32_t indexSectionOffset;
++ uint32_t indexCount;
++ // compact_unwind_encoding_t[]
++ // uint32_t personalities[]
++ // unwind_info_section_header_index_entry[]
++ // unwind_info_section_header_lsda_index_entry[]
++};
++
++struct unwind_info_section_header_index_entry
++{
++ uint32_t functionOffset;
++ uint32_t secondLevelPagesSectionOffset; // section offset to start of regular or compress page
++ uint32_t lsdaIndexArraySectionOffset; // section offset to start of lsda_index array for this range
++};
++
++struct unwind_info_section_header_lsda_index_entry
++{
++ uint32_t functionOffset;
++ uint32_t lsdaOffset;
++};
++
++//
++// There are two kinds of second level index pages: regular and compressed.
++// A compressed page can hold up to 1021 entries, but it cannot be used
++// if too many different encoding types are used. The regular page holds
++// 511 entries.
++//
++
++struct unwind_info_regular_second_level_entry
++{
++ uint32_t functionOffset;
++ compact_unwind_encoding_t encoding;
++};
++
++#define UNWIND_SECOND_LEVEL_REGULAR 2
++struct unwind_info_regular_second_level_page_header
++{
++ uint32_t kind; // UNWIND_SECOND_LEVEL_REGULAR
++ uint16_t entryPageOffset;
++ uint16_t entryCount;
++ // entry array
++};
++
++#define UNWIND_SECOND_LEVEL_COMPRESSED 3
++struct unwind_info_compressed_second_level_page_header
++{
++ uint32_t kind; // UNWIND_SECOND_LEVEL_COMPRESSED
++ uint16_t entryPageOffset;
++ uint16_t entryCount;
++ uint16_t encodingsPageOffset;
++ uint16_t encodingsCount;
++ // 32-bit entry array
++ // encodings array
++};
++
++#define UNWIND_INFO_COMPRESSED_ENTRY_FUNC_OFFSET(entry) (entry & 0x00FFFFFF)
++#define UNWIND_INFO_COMPRESSED_ENTRY_ENCODING_INDEX(entry) ((entry >> 24) & 0xFF)
++
++
++
++#endif
++
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