[lld] [lld][elf] add safe-thunks in ELF (PR #126695)

[Peter Smith via llvm-commits]

================
@@ -0,0 +1,397 @@
+# REQUIRES: aarch64
+# RUN: rm -rf %t && split-file %s %t && cd %t
+
+# RUN: llvm-mc -filetype=obj -triple=aarch64 a.s -o a.o
+# RUN: ld.lld a.o -o a.so --icf=safe_thunks --print-icf-sections | FileCheck %s
+# RUN: llvm-objdump a.so -d | FileCheck %s --check-prefixes=CHECK-ARM64
+
+# CHECK: selected section a.o:(.text.func_3identical_v1_canmerge)
+# CHECK: selected section a.o:(.text.func_call_thunked_1_nomerge)
+# CHECK: selected section a.o:(.text.func_unique_2_canmerge)
+# CHECK: selected section a.o:(.text.func_3identical_v1)
+
+# CHECK-ARM64: func_unique_1
+# CHECK-ARM64-NEXT: adrp    x8, {{.*}}
+# CHECK-ARM64-NEXT: mov     w9, #0x1
+
+# CHECK-ARM64: func_unique_2_canmerge
+# CHECK-ARM64-NEXT: adrp    x8, {{.*}}
+# CHECK-ARM64-NEXT: mov     w9, #0x2
+
+# CHECK-ARM64: func_3identical_v1
+# CHECK-ARM64-NEXT: adrp    x8, {{.*}}
+# CHECK-ARM64-NEXT: mov     w9, #0x3
+
+# CHECK-ARM64: func_3identical_v1_canmerge
+# CHECK-ARM64-NEXT: adrp    x8, {{.*}}
+
+# CHECK-ARM64: func_call_thunked_1_nomerge
+# CHECK-ARM64-NEXT: stp     x29, x30, [sp, #-0x10]!
+
+# CHECK-ARM64: <func_3identical_v2_canmerge>:
+# CHECK-ARM64-NEXT: b       0x[[#%.6x,]] <func_3identical_v1_canmerge>
+# CHECK-ARM64: <func_3identical_v3_canmerge>:
+# CHECK-ARM64-NEXT: b       0x[[#%.6x,]] <func_3identical_v1_canmerge>
+# CHECK-ARM64: <func_call_thunked_2_nomerge>:
+# CHECK-ARM64-NEXT: b       0x[[#%.6x,]] <func_call_thunked_1_nomerge>
+# CHECK-ARM64: <func_call_thunked_2_merge>:
+# CHECK-ARM64-NEXT: b       0x[[#%.6x,]] <func_call_thunked_1_nomerge>
+# CHECK-ARM64: <func_2identical_v1>:
+# CHECK-ARM64-NEXT: b       0x[[#%.6x,]] <func_unique_2_canmerge>
+# CHECK-ARM64: <func_2identical_v2>:
+# CHECK-ARM64-NEXT: b       0x[[#%.6x,]] <func_unique_2_canmerge>
+# CHECK-ARM64: <func_3identical_v2>:
+# CHECK-ARM64-NEXT: b       0x[[#%.6x,]] <func_3identical_v1>
+# CHECK-ARM64: <func_3identical_v3>:
+# CHECK-ARM64-NEXT: b       0x[[#%.6x,]] <func_3identical_v1>
+
+;--- a.cc
+#define ATTR __attribute__((noinline,used,retain)) extern "C"
+typedef unsigned long long ULL;
+
+volatile char g_val = 0;
+void *volatile g_ptr = 0;
+
+ATTR void func_unique_1() { g_val = 1; }
+
+ATTR void func_unique_2_canmerge() { g_val = 2; }
+
+ATTR void func_2identical_v1() { g_val = 2; }
+
+ATTR void func_2identical_v2() { g_val = 2; }
+
+ATTR void func_3identical_v1() { g_val = 3; }
+
+ATTR void func_3identical_v2() { g_val = 3; }
+
+ATTR void func_3identical_v3() { g_val = 3; }
+
+ATTR void func_3identical_v1_canmerge() { g_val = 33; }
+
+ATTR void func_3identical_v2_canmerge() { g_val = 33; }
+
+ATTR void func_3identical_v3_canmerge() { g_val = 33; }
+
+ATTR void func_call_thunked_1_nomerge() {
+    func_2identical_v1();
+    g_val = 77;
+}
+
+ATTR void func_call_thunked_2_nomerge() {
+    func_2identical_v2();
+    g_val = 77;
+}
+
+ATTR void func_call_thunked_2_merge() {
+    func_2identical_v2();
+    g_val = 77;
+}
+
+ATTR void call_all_funcs() {
+    func_unique_1();
+    func_unique_2_canmerge();
+    func_2identical_v1();
+    func_2identical_v2();
+    func_3identical_v1();
+    func_3identical_v2();
+    func_3identical_v3();
+    func_3identical_v1_canmerge();
+    func_3identical_v2_canmerge();
+    func_3identical_v3_canmerge();
+}
+
+ATTR void take_func_addr() {
+    g_ptr = (void*)func_unique_1;
+    g_ptr = (void*)func_2identical_v1;
+    g_ptr = (void*)func_2identical_v2;
+    g_ptr = (void*)func_3identical_v1;
+    g_ptr = (void*)func_3identical_v2;
+    g_ptr = (void*)func_3identical_v3;
+}
+
+ATTR int _start() { return 0; }
+
+;--- gen
+clang --target=aarch64-linux-gnu -O3 -ffunction-sections -fdata-sections -fno-asynchronous-unwind-tables -S a.cc -o -
----------------
smithp35 wrote:

The lld tests can't use clang as the tests can be run without building clang. Essentially anything that is built as a result of `-DLLVM_ENABLE_PROJECTS="lld"` (and no runtimes) can be used.

https://github.com/llvm/llvm-project/pull/126695