[darwin][driver] Pass through -global-isel LLVM flags to ld.

GlobalISel is currently not enabled when using -flto since the front-end
-mvllm flags don't get passed through. This change fixes this for Darwin
platforms. We have to do this in the driver because the code generator choice
isn't embedded into the bitcode file.

Differential Revision: https://reviews.llvm.org/D99126

diff --git a/clang/lib/Driver/ToolChains/Darwin.cpp b/clang/lib/Driver/ToolChains/Darwin.cpp
index a09a69f..bc59b6b 100644 (file)
--- a/clang/lib/Driver/ToolChains/Darwin.cpp
+++ b/clang/lib/Driver/ToolChains/Darwin.cpp
@@ -373,6 +373,18 @@ void darwin::Linker::AddLinkArgs(Compilation &C, const ArgList &Args,
       D.Diag(diag::err_drv_bitcode_unsupported_on_toolchain);
   }
 
+  // If GlobalISel is enabled, pass it through to LLVM.
+  if (Arg *A = Args.getLastArg(options::OPT_fglobal_isel,
+                               options::OPT_fno_global_isel)) {
+    if (A->getOption().matches(options::OPT_fglobal_isel)) {
+      CmdArgs.push_back("-mllvm");
+      CmdArgs.push_back("-global-isel");
+      // Disable abort and fall back to SDAG silently.
+      CmdArgs.push_back("-mllvm");
+      CmdArgs.push_back("-global-isel-abort=0");
+    }
+  }
+
   Args.AddLastArg(CmdArgs, options::OPT_prebind);
   Args.AddLastArg(CmdArgs, options::OPT_noprebind);
   Args.AddLastArg(CmdArgs, options::OPT_nofixprebinding);

diff --git a/clang/test/Driver/darwin-ld-lto.c b/clang/test/Driver/darwin-ld-lto.c
index 05e6bcc..252ca14 100644 (file)
--- a/clang/test/Driver/darwin-ld-lto.c
+++ b/clang/test/Driver/darwin-ld-lto.c
@@ -30,3 +30,11 @@
 // THIN_LTO_OBJECT_PATH: {{ld(.exe)?"}}
 // THIN_LTO_OBJECT_PATH-SAME: "-object_path_lto"
 // THIN_LTO_OBJECT_PATH-SAME: {{thinlto\-[a-zA-Z0-9_]+}}
+
+
+// Check that we pass through -fglobal-isel flags to libLTO.
+// RUN: %clang -target arm64-apple-darwin %s -flto -fglobal-isel -### 2>&1 | \
+// RUN:   FileCheck --check-prefix=GISEL %s
+// GISEL: {{ld(.exe)?"}}
+// GISEL: "-mllvm" "-global-isel"
+// GISEL: "-mllvm" "-global-isel-abort=0"