[PATCH] D99126: [darwin][driver] Pass through -global-isel LLVM flags to ld.

[Amara Emerson via Phabricator via cfe-commits]

aemerson created this revision.
aemerson added reviewers: paquette, ahmed, qcolombet, pete.
aemerson added a project: clang.
Herald added subscribers: steven_wu, hiraditya.
aemerson requested review of this revision.

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.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D99126

Files:
  clang/lib/Driver/ToolChains/Darwin.cpp
  clang/test/Driver/darwin-ld-lto.c


Index: clang/test/Driver/darwin-ld-lto.c
===================================================================
--- clang/test/Driver/darwin-ld-lto.c
+++ 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"
Index: clang/lib/Driver/ToolChains/Darwin.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Darwin.cpp
+++ clang/lib/Driver/ToolChains/Darwin.cpp
@@ -373,6 +373,18 @@
       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);


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