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Merge pull request #20872 from alexrp/riscv-gp

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start: Initialize `gp` to `__global_pointer$` on riscv.
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Andrew Kelley 2024-08-01 00:47:05 -07:00 committed by GitHub
commit 63aa85e7af
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1 changed files with 15 additions and 2 deletions
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17
lib/std/start.zig
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@ -272,13 +272,27 @@ fn _start() callconv(.Naked) noreturn {
\\ bstrins.d $sp, $zero, 3, 0
\\ b %[posixCallMainAndExit]
,
// zig fmt: off
.riscv32, .riscv64 =>
// The self-hosted riscv64 backend is not able to assemble this yet.
if (builtin.zig_backend != .stage2_riscv64)
// The RISC-V ELF ABI assumes that `gp` is set to the value of `__global_pointer$` at
// startup in order for GP relaxation to work, even in static builds.
\\ .weak __global_pointer$
\\ .hidden __global_pointer$
\\ .option push
\\ .option norelax
\\ lla gp, __global_pointer$
\\ .option pop
else ""
++
\\ li s0, 0
\\ li ra, 0
\\ mv a0, sp
\\ andi sp, sp, -16
\\ tail %[posixCallMainAndExit]@plt
,
// zig fmt: off
.m68k =>
// Note that the - 8 is needed because pc in the jsr instruction points into the middle
// of the jsr instruction. (The lea is 6 bytes, the jsr is 4 bytes.)
@ -293,6 +307,7 @@ fn _start() callconv(.Naked) noreturn {
\\ .gpword .
\\ .gpword %[posixCallMainAndExit]
\\ 1:
// The `gp` register on MIPS serves a similar purpose to `r2` (ToC pointer) on PPC64.
\\ lw $gp, 0($ra)
\\ subu $gp, $ra, $gp
\\ lw $25, 4($ra)
@ -314,8 +329,6 @@ fn _start() callconv(.Naked) noreturn {
\\ .gpdword %[posixCallMainAndExit]
\\ 1:
// The `gp` register on MIPS serves a similar purpose to `r2` (ToC pointer) on PPC64.
// We need to set it up in order for dynamically-linked / position-independent code to
// work.
\\ ld $gp, 0($ra)
\\ dsubu $gp, $ra, $gp
\\ ld $25, 8($ra)