From 77fc3b88fbdf805e0c2c1fc2647513cee56813a4 Mon Sep 17 00:00:00 2001
From: Alex Rønne Petersen <alex@alexrp.com>
Date: Thu, 25 Jul 2024 01:08:03 +0200
Subject: start: Set up the gp register on mips and mips64.

---
 lib/std/start.zig | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'lib/std')

diff --git a/lib/std/start.zig b/lib/std/start.zig
index 326857d9c0..78845904d6 100644
--- a/lib/std/start.zig
+++ b/lib/std/start.zig
@@ -329,6 +329,11 @@ fn _start() callconv(.Naked) noreturn {
             \\ jsr (%%pc, %%a0)
             ,
             .mips, .mipsel =>
+            \\ bal 1f
+            \\ .gpword .
+            \\ 1:
+            \\ lw $gp, 0($ra)
+            \\ subu $gp, $ra, $gp
             \\ move $fp, $0
             \\ move $ra, $0
             \\ move $a0, $sp
@@ -336,6 +341,14 @@ fn _start() callconv(.Naked) noreturn {
             \\ j %[posixCallMainAndExit]
             ,
             .mips64, .mips64el =>
+            \\ bal 1f
+            \\ .gpdword .
+            \\ 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
             \\ move $fp, $0
             \\ move $ra, $0
             \\ move $a0, $sp
-- 
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