authorgravatar for andrew@ziglang.orgAndrew Kelley <andrew@ziglang.org> 2024-08-01 00:47:05-07:00
committergravatar for noreply@github.comGitHub <noreply@github.com> 2024-08-01 00:47:05-07:00
log63aa85e7afb37d0b2b5c48309ef1a88d8fd444b5
tree65ae842b0bc28adfa9e81eda7dcde46c753501f6
parent8ea323822ba1fc2f54940841b2cedb3494230a3c
parent653eb7535514d06aca1eaaf777f82e1ecd968086
signaturebadge-check Signed by PGP key B5690EEEBB952194

Merge pull request #20872 from alexrp/riscv-gp

start: Initialize `gp` to `__global_pointer$` on riscv.

1 files changed, 15 insertions(+), 2 deletions(-)

lib/std/start.zig+15-2
......@@ -272,13 +272,27 @@ fn _start() callconv(.Naked) noreturn {
272272 \\ bstrins.d $sp, $zero, 3, 0
273273 \\ b %[posixCallMainAndExit]
274274 ,
275 // zig fmt: off
275276 .riscv32, .riscv64 =>
277 // The self-hosted riscv64 backend is not able to assemble this yet.
278 if (builtin.zig_backend != .stage2_riscv64)
279 // The RISC-V ELF ABI assumes that `gp` is set to the value of `__global_pointer$` at
280 // startup in order for GP relaxation to work, even in static builds.
281 \\ .weak __global_pointer$
282 \\ .hidden __global_pointer$
283 \\ .option push
284 \\ .option norelax
285 \\ lla gp, __global_pointer$
286 \\ .option pop
287 else ""
288 ++
276289 \\ li s0, 0
277290 \\ li ra, 0
278291 \\ mv a0, sp
279292 \\ andi sp, sp, -16
280293 \\ tail %[posixCallMainAndExit]@plt
281294 ,
295 // zig fmt: off
282296 .m68k =>
283297 // Note that the - 8 is needed because pc in the jsr instruction points into the middle
284298 // of the jsr instruction. (The lea is 6 bytes, the jsr is 4 bytes.)
......@@ -293,6 +307,7 @@ fn _start() callconv(.Naked) noreturn {
293307 \\ .gpword .
294308 \\ .gpword %[posixCallMainAndExit]
295309 \\ 1:
310 // The `gp` register on MIPS serves a similar purpose to `r2` (ToC pointer) on PPC64.
296311 \\ lw $gp, 0($ra)
297312 \\ subu $gp, $ra, $gp
298313 \\ lw $25, 4($ra)
......@@ -314,8 +329,6 @@ fn _start() callconv(.Naked) noreturn {
314329 \\ .gpdword %[posixCallMainAndExit]
315330 \\ 1:
316331 // The `gp` register on MIPS serves a similar purpose to `r2` (ToC pointer) on PPC64.
317 // We need to set it up in order for dynamically-linked / position-independent code to
318 // work.
319332 \\ ld $gp, 0($ra)
320333 \\ dsubu $gp, $ra, $gp
321334 \\ ld $25, 8($ra)