[LLD] Fix issue in HIP toolchain due to unspecified order of evaluation of the function object

[aganea]

Summary

This fixes the issue raised in https://reviews.llvm.org/D108850#3303452

Before C++17, the function object is evaluated in a unspecified order. In the following example: https://godbolt.org/z/8ao4vdsr7 the function object is either evaluated before or after the arguments, depending on the compiler. With MSVC and /std:c++14 the function object is evaluated after the arguments; with clang and gcc, it is evaluated before. With C++17, the function object is guaranteed to be evaluated before the arguments, see: https://riptutorial.com/cplusplus/example/19369/evaluation-order-of-function-arguments

In our case, the issue was that the args conversion to ArrayRef as evaluated before the lambda call link, which internally was calling parseFlavor(), which in turned modified args. We ended with an ArrayRef argument that reflected the previous value of args.

Add coverage for -flavor which we didn't have before.

[yaxunl]

LGTM. Thanks.

[MaskRay]

lld/test/ELF/amdgpu-duplicate-sym.s

10

Remove unneeded directives like .p2alignl, .fill, .size

21

remove

[MaskRay]

Thanks!

[aganea]

lld/test/ELF/amdgpu-duplicate-sym.s

10

Both comments fixed in the commit, thanks for reviewing!

lld/test/ELF/amdgpu-duplicate-sym.s

+# REQUIRES: amdgpu
+# RUN: llvm-mc -filetype=obj -triple amdgcn-amd-amdhsa -mcpu=gfx1031 --position-independent --relax-relocations %s -o %t.o
+
+# We use lld-link on purpose to exercise -flavor.
+# RUN: lld-link -flavor gnu -shared %t.o
+
+        .text
+        .amdgcn_target "amdgcn-amd-amdhsa--gfx1031"
+        .protected      xxx                     ; @xxx
+        .type   xxx,@object
+        .data
+        .globl  xxx
+xxx:
+        .long   123                             ; 0x7b
+
+        .addrsig
+        .amdgpu_metadata
+---
+amdhsa.kernels:  []
+amdhsa.target:   amdgcn-amd-amdhsa--gfx1031
+amdhsa.version:
+  - 1
+  - 1
+...
+
+        .end_amdgpu_metadata

lld/tools/lld/lld.cpp

auto link = [&args]() {
     else if (f == Darwin)
       return macho::link;
     else if (f == Wasm)
       return lld::wasm::link;
     else
       die("lld is a generic driver.\n"
           "Invoke ld.lld (Unix), ld64.lld (macOS), lld-link (Windows), wasm-ld"
           " (WebAssembly) instead");
-  };
+  }();
   // Run the driver. If an error occurs, false will be returned.
-  bool r = link()(args, stdoutOS, stderrOS, exitEarly, inTestOutputDisabled);
+  bool r = link(args, stdoutOS, stderrOS, exitEarly, inTestOutputDisabled);
 
   // Call exit() if we can to avoid calling destructors.
   if (exitEarly)
     exitLld(!r ? 1 : 0);
 
   // Delete the global context and clear the global context pointer, so that it
   // cannot be accessed anymore.
   CommonLinkerContext::destroy();