Magic-Mirror/llvm-capstone
1
0
Fork 0
mirror of https://github.com/capstone-engine/llvm-capstone.git synced 2024-12-01 09:41:08 +00:00
Code Issues Actions 2 Packages Projects Releases Wiki Activity

[lld][RISCV] Implement GP relaxation for R_RISCV_HI20/R_RISCV_LO12_I/R_RISCV_LO12_S.

Browse Source 
This implements support for relaxing these relocations to use the GP
register to compute addresses of globals in the .sdata and .sbss
sections.

This feature is off by default and must be enabled by passing
--relax-gp to the linker.

The GP register might not always be the "global pointer". It can
be used for other purposes. See discussion here
https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/371

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D143673
This commit is contained in:
Craig Topper 2023-04-13 10:39:47 -07:00
parent b60513e384
commit 85444794cd
10 changed files with 177 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
lld/ELF/Arch/RISCV.cpp
View File

@ -48,6 +48,11 @@ public:
} // end anonymous namespace
// These are internal relocation numbers for GP relaxation. They aren't part
// of the psABI spec.
#define INTERNAL_R_RISCV_GPREL_I 256
#define INTERNAL_R_RISCV_GPREL_S 257
const uint64_t dtpOffset = 0x800;
enum Op {
@ -62,6 +67,7 @@ enum Op {
enum Reg {
X_RA = 1,
X_GP = 3,
X_TP = 4,
X_T0 = 5,
X_T1 = 6,
@ -436,6 +442,20 @@ void RISCV::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
return;
}
case INTERNAL_R_RISCV_GPREL_I:
case INTERNAL_R_RISCV_GPREL_S: {
Defined *gp = ElfSym::riscvGlobalPointer;
int64_t displace = SignExtend64(val - gp->getVA(), bits);
checkInt(loc, displace, 12, rel);
uint32_t insn = (read32le(loc) & ~(31 << 15)) | (X_GP << 15);
if (rel.type == INTERNAL_R_RISCV_GPREL_I)
insn = setLO12_I(insn, displace);
else
insn = setLO12_S(insn, displace);
write32le(loc, insn);
return;
}
case R_RISCV_ADD8:
*loc += val;
return;
@ -614,6 +634,30 @@ static void relaxTlsLe(const InputSection &sec, size_t i, uint64_t loc,
}
}
static void relaxHi20Lo12(const InputSection &sec, size_t i, uint64_t loc,
Relocation &r, uint32_t &remove) {
const Defined *gp = ElfSym::riscvGlobalPointer;
if (!gp)
return;
if (!isInt<12>(r.sym->getVA(r.addend) - gp->getVA()))
return;
switch (r.type) {
case R_RISCV_HI20:
// Remove lui rd, %hi20(x).
sec.relaxAux->relocTypes[i] = R_RISCV_RELAX;
remove = 4;
break;
case R_RISCV_LO12_I:
sec.relaxAux->relocTypes[i] = INTERNAL_R_RISCV_GPREL_I;
break;
case R_RISCV_LO12_S:
sec.relaxAux->relocTypes[i] = INTERNAL_R_RISCV_GPREL_S;
break;
}
}
static bool relax(InputSection &sec) {
const uint64_t secAddr = sec.getVA();
auto &aux = *sec.relaxAux;
@ -665,6 +709,13 @@ static bool relax(InputSection &sec) {
sec.relocs()[i + 1].type == R_RISCV_RELAX)
relaxTlsLe(sec, i, loc, r, remove);
break;
case R_RISCV_HI20:
case R_RISCV_LO12_I:
case R_RISCV_LO12_S:
if (i + 1 != sec.relocs().size() &&
sec.relocs()[i + 1].type == R_RISCV_RELAX)
relaxHi20Lo12(sec, i, loc, r, remove);
break;
}
// For all anchors whose offsets are <= r.offset, they are preceded by
@ -778,6 +829,9 @@ void elf::riscvFinalizeRelax(int passes) {
}
} else if (RelType newType = aux.relocTypes[i]) {
switch (newType) {
case INTERNAL_R_RISCV_GPREL_I:
case INTERNAL_R_RISCV_GPREL_S:
break;
case R_RISCV_RELAX:
// Used by relaxTlsLe to indicate the relocation is ignored.
break;

1
lld/ELF/Config.h
View File

@ -253,6 +253,7 @@ struct Config {
bool printGcSections;
bool printIcfSections;
bool relax;
bool relaxGP;
bool relocatable;
bool relrGlibc = false;
bool relrPackDynRelocs = false;

4
lld/ELF/Driver.cpp
View File

@ -357,6 +357,9 @@ static void checkOptions() {
if (config->pcRelOptimize && config->emachine != EM_PPC64)
error("--pcrel-optimize is only supported on PowerPC64 targets");
if (config->relaxGP && config->emachine != EM_RISCV)
error("--relax-gp is only supported on RISC-V targets");
if (config->pie && config->shared)
error("-shared and -pie may not be used together");
@ -1217,6 +1220,7 @@ static void readConfigs(opt::InputArgList &args) {
config->printSymbolOrder =
args.getLastArgValue(OPT_print_symbol_order);
config->relax = args.hasFlag(OPT_relax, OPT_no_relax, true);
config->relaxGP = args.hasFlag(OPT_relax_gp, OPT_no_relax_gp, false);
config->rpath = getRpath(args);
config->relocatable = args.hasArg(OPT_relocatable);

4
lld/ELF/Options.td
View File

@ -355,6 +355,10 @@ defm relax: BB<"relax",
"Enable target-specific relaxations if supported (default)",
"Disable target-specific relaxations">;
defm relax_gp: BB<"relax-gp",
"Enable global pointer relaxation",
"Disable global pointer relaxation (default)">;
defm reproduce:
EEq<"reproduce",
"Write tar file containing inputs and command to reproduce link">;

1
lld/ELF/Symbols.cpp
View File

@ -71,6 +71,7 @@ Defined *ElfSym::globalOffsetTable;
Defined *ElfSym::mipsGp;
Defined *ElfSym::mipsGpDisp;
Defined *ElfSym::mipsLocalGp;
Defined *ElfSym::riscvGlobalPointer;
Defined *ElfSym::relaIpltStart;
Defined *ElfSym::relaIpltEnd;
Defined *ElfSym::tlsModuleBase;

3
lld/ELF/Symbols.h
View File

@ -512,6 +512,9 @@ struct ElfSym {
static Defined *mipsGpDisp;
static Defined *mipsLocalGp;
// __global_pointer$ for RISC-V.
static Defined *riscvGlobalPointer;
// __rel{,a}_iplt_{start,end} symbols.
static Defined *relaIpltStart;
static Defined *relaIpltEnd;

18
lld/ELF/Writer.cpp
View File

@ -1872,10 +1872,20 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
// should only be defined in an executable. If .sdata does not exist, its
// value/section does not matter but it has to be relative, so set its
// st_shndx arbitrarily to 1 (Out::elfHeader).
if (config->emachine == EM_RISCV && !config->shared) {
OutputSection *sec = findSection(".sdata");
addOptionalRegular("__global_pointer$", sec ? sec : Out::elfHeader, 0x800,
STV_DEFAULT);
if (config->emachine == EM_RISCV) {
ElfSym::riscvGlobalPointer = nullptr;
if (!config->shared) {
OutputSection *sec = findSection(".sdata");
addOptionalRegular(
"__global_pointer$", sec ? sec : Out::elfHeader, 0x800, STV_DEFAULT);
// Set riscvGlobalPointer to be used by the optional global pointer
// relaxation.
if (config->relaxGP) {
Symbol *s = symtab.find("__global_pointer$");
if (s && s->isDefined())
ElfSym::riscvGlobalPointer = cast<Defined>(s);
}
}
}
if (config->emachine == EM_386 || config->emachine == EM_X86_64) {

2
lld/docs/ld.lld.1
View File

@ -493,6 +493,8 @@ and
.It Fl -pop-state
Restore the states saved by
.Fl -push-state.
.It Fl --relax-gp
Enable global pointer relaxation for RISC-V.
.It Fl -relocatable , Fl r
Create relocatable object file.
.It Fl -reproduce Ns = Ns Ar path

33
lld/test/ELF/riscv-relax-hi20-lo12-pie.s Normal file
View File

@ -0,0 +1,33 @@
# REQUIRES: riscv
# RUN: rm -rf %t && split-file %s %t && cd %t
# RUN: llvm-mc -filetype=obj -triple=riscv32-unknown-elf -mattr=+relax a.s -o rv32.o
# RUN: llvm-mc -filetype=obj -triple=riscv64-unknown-elf -mattr=+relax a.s -o rv64.o
# RUN: llvm-mc -filetype=obj -triple=riscv64-unknown-elf -mattr=+relax a.s -o rv64-pie.o
# RUN: ld.lld --relax-gp --undefined=__global_pointer$ rv32.o lds -pie -o rv32
# RUN: ld.lld --relax-gp --undefined=__global_pointer$ rv64.o lds -shared -o rv64
# RUN: llvm-objdump -td -M no-aliases --no-show-raw-insn rv32 | FileCheck %s
# RUN: llvm-objdump -td -M no-aliases --no-show-raw-insn rv64 | FileCheck %s
# CHECK: lui a0, 512
# CHECK-NEXT: addi a0, a0, 1
# CHECK-NEXT: lw a0, 1(a0)
# CHECK-NEXT: sw a0, 1(a0)
#--- a.s
.globl abs
abs = 0x200001
.global _start
_start:
lui a0, %hi(abs)
addi a0, a0, %lo(abs)
lw a0, %lo(abs)(a0)
sw a0, %lo(abs)(a0)
#--- lds
SECTIONS {
.text : {*(.text) }
.sdata 0x200000 : {}
}

61
lld/test/ELF/riscv-relax-hi20-lo12.s Normal file
View File

@ -0,0 +1,61 @@
# REQUIRES: riscv
# RUN: rm -rf %t && split-file %s %t && cd %t
# RUN: llvm-mc -filetype=obj -triple=riscv32-unknown-elf -mattr=+relax a.s -o rv32.o
# RUN: llvm-mc -filetype=obj -triple=riscv64-unknown-elf -mattr=+relax a.s -o rv64.o
# RUN: ld.lld --relax-gp --undefined=__global_pointer$ rv32.o lds -o rv32
# RUN: ld.lld --relax-gp --undefined=__global_pointer$ rv64.o lds -o rv64
# RUN: llvm-objdump -td -M no-aliases --no-show-raw-insn rv32 | FileCheck %s
# RUN: llvm-objdump -td -M no-aliases --no-show-raw-insn rv64 | FileCheck %s
# CHECK: 00000028 l .text {{0*}}0 a
# CHECK-NOT: lui
# CHECK: addi a0, gp, -2048
# CHECK-NEXT: lw a0, -2048(gp)
# CHECK-NEXT: sw a0, -2048(gp)
# CHECK-NOT: lui
# CHECK-NEXT: addi a0, gp, 2047
# CHECK-NEXT: lb a0, 2047(gp)
# CHECK-NEXT: sb a0, 2047(gp)
# CHECK-NEXT: lui a0, 513
# CHECK-NEXT: addi a0, a0, 0
# CHECK-NEXT: lw a0, 0(a0)
# CHECK-NEXT: sw a0, 0(a0)
# CHECK-EMPTY:
# CHECK-NEXT: <a>:
# CHECK-NEXT: addi a0, a0, 1
#--- a.s
.global _start
_start:
lui a0, %hi(foo)
addi a0, a0, %lo(foo)
lw a0, %lo(foo)(a0)
sw a0, %lo(foo)(a0)
lui a0, %hi(bar)
addi a0, a0, %lo(bar)
lb a0, %lo(bar)(a0)
sb a0, %lo(bar)(a0)
lui a0, %hi(norelax)
addi a0, a0, %lo(norelax)
lw a0, %lo(norelax)(a0)
sw a0, %lo(norelax)(a0)
a:
addi a0, a0, 1
.section .sdata,"aw"
foo:
.word 0
.space 4091
bar:
.byte 0
norelax:
.word 0
#--- lds
SECTIONS {
.text : {*(.text) }
.sdata 0x200000 : { }
}