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Merge pull request #20718 from alexrp/start-gv

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`start`: Avoid going through the argc_argv_ptr global variable
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Andrew Kelley 2024-07-22 00:24:50 -07:00 committed by GitHub
commit b149d8f747
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1 changed files with 17 additions and 16 deletions
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33
lib/std/start.zig
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@ -9,8 +9,6 @@ const elf = std.elf;
const native_arch = builtin.cpu.arch;
const native_os = builtin.os.tag;
var argc_argv_ptr: [*]usize = undefined;
const start_sym_name = if (native_arch.isMIPS()) "__start" else "_start";
// The self-hosted compiler is not fully capable of handling all of this start.zig file.
@ -277,41 +275,42 @@ fn _start() callconv(.Naked) noreturn {
asm volatile (switch (native_arch) {
.x86_64 =>
\\ xorl %%ebp, %%ebp
\\ movq %%rsp, %[argc_argv_ptr]
\\ movq %%rsp, %%rdi
\\ andq $-16, %%rsp
\\ callq %[posixCallMainAndExit:P]
,
.x86 =>
\\ xorl %%ebp, %%ebp
\\ movl %%esp, %[argc_argv_ptr]
\\ movl %%esp, %%eax
\\ andl $-16, %%esp
\\ subl $12, %%esp
\\ pushl %%eax
\\ calll %[posixCallMainAndExit:P]
,
.aarch64, .aarch64_be =>
\\ mov fp, #0
\\ mov lr, #0
\\ mov x0, sp
\\ str x0, %[argc_argv_ptr]
\\ b %[posixCallMainAndExit]
,
.arm, .armeb, .thumb, .thumbeb =>
\\ mov fp, #0
\\ mov lr, #0
\\ str sp, %[argc_argv_ptr]
\\ mov a1, sp
\\ and sp, #-16
\\ b %[posixCallMainAndExit]
,
.riscv64 =>
\\ li s0, 0
\\ li ra, 0
\\ sd sp, %[argc_argv_ptr]
\\ mv a0, sp
\\ andi sp, sp, -16
\\ tail %[posixCallMainAndExit]@plt
,
.mips, .mipsel =>
// The lr is already zeroed on entry, as specified by the ABI.
\\ addiu $fp, $zero, 0
\\ sw $sp, %[argc_argv_ptr]
\\ move $a0, $sp
\\ .set push
\\ .set noat
\\ addiu $1, $zero, -16
@ -322,7 +321,7 @@ fn _start() callconv(.Naked) noreturn {
.mips64, .mips64el =>
// The lr is already zeroed on entry, as specified by the ABI.
\\ addiu $fp, $zero, 0
\\ sd $sp, %[argc_argv_ptr]
\\ move $a0, $sp
\\ .set push
\\ .set noat
\\ daddiu $1, $zero, -16
@ -332,7 +331,7 @@ fn _start() callconv(.Naked) noreturn {
,
.powerpc, .powerpcle =>
// Setup the initial stack frame and clear the back chain pointer.
\\ stw 1, %[argc_argv_ptr]
\\ mr 3, 1
\\ li 0, 0
\\ stwu 1, -16(1)
\\ stw 0, 0(1)
@ -341,8 +340,10 @@ fn _start() callconv(.Naked) noreturn {
,
.powerpc64, .powerpc64le =>
// Setup the initial stack frame and clear the back chain pointer.
// TODO: Support powerpc64 (big endian) on ELFv2.
\\ std 1, %[argc_argv_ptr]
\\ addis 2, 12, .TOC. - _start@ha
\\ addi 2, 2, .TOC. - _start@l
\\ mr 3, 1
\\ clrrdi 1, 1, 4
\\ li 0, 0
\\ stdu 0, -32(1)
\\ mtlr 0
@ -352,12 +353,12 @@ fn _start() callconv(.Naked) noreturn {
// argc is stored after a register window (16 registers) plus stack bias
\\ mov %%g0, %%i6
\\ add %%o6, 2175, %%l0
\\ ba %[posixCallMainAndExit]
\\ stx %%l0, %[argc_argv_ptr]
\\ mov %%l0, %%o0
\\ ba,a %[posixCallMainAndExit]
,
else => @compileError("unsupported arch"),
}
: [argc_argv_ptr] "=m" (argc_argv_ptr),
:
: [posixCallMainAndExit] "X" (&posixCallMainAndExit),
);
}
@ -385,7 +386,7 @@ fn wWinMainCRTStartup() callconv(std.os.windows.WINAPI) noreturn {
std.os.windows.ntdll.RtlExitUserProcess(@as(std.os.windows.UINT, @bitCast(result)));
}
fn posixCallMainAndExit() callconv(.C) noreturn {
fn posixCallMainAndExit(argc_argv_ptr: [*]usize) callconv(.C) noreturn {
const argc = argc_argv_ptr[0];
const argv = @as([*][*:0]u8, @ptrCast(argc_argv_ptr + 1));