[llvm] [BOLT][RISCV] Precommit test for a call that links through t0 (PR #218396)

[Kito Cheng via llvm-commits]

https://github.com/kito-cheng created https://github.com/llvm/llvm-project/pull/218396

The machine outliner calls its outlined functions with "call t0, func" and the callee returns with "jr t0". BOLT currently rewrites that call to link through ra, which the CHECK lines below pin down.

>From 710380d1211cb641fa7ebb98b6165ccfdfbaee45 Mon Sep 17 00:00:00 2001
From: Kito Cheng <kito.cheng at sifive.com>
Date: Mon, 17 Aug 2026 23:29:39 +0800
Subject: [PATCH] [BOLT][RISCV] Precommit test for a call that links through t0

The machine outliner calls its outlined functions with "call t0, func" and
the callee returns with "jr t0". BOLT currently rewrites that call to link
through ra, which the CHECK lines below pin down.
---
 bolt/test/RISCV/call-link-register.s | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 bolt/test/RISCV/call-link-register.s

diff --git a/bolt/test/RISCV/call-link-register.s b/bolt/test/RISCV/call-link-register.s
new file mode 100644
index 0000000000000..50288e3bd31d3
--- /dev/null
+++ b/bolt/test/RISCV/call-link-register.s
@@ -0,0 +1,24 @@
+// RUN: %clang %cflags64 -Wl,--no-relax -o %t %s
+// RUN: llvm-bolt -o %t.bolt %t
+// RUN: llvm-objdump -d --disassemble-symbols=_start %t.bolt | FileCheck %s
+
+  .text
+
+  .globl _start
+  .p2align 1
+_start:
+// CHECK-LABEL: <_start>:
+/// The auipc of the pair, replaced by a nop once the call is rewritten.
+// CHECK-NEXT: nop
+/// FIXME: the link register is dropped here: the call is rewritten to link
+/// through ra, so f returns to whatever t0 happens to hold.
+// CHECK-NEXT: jal 0x{{.*}} <f>
+  call t0, f
+  ret
+  .size _start, .-_start
+
+  .globl f
+  .p2align 1
+f:
+  jr t0
+  .size f, .-f