[Clang][LTO][GISel] Propagate -fglobal-siel to LTO

[mshockwave]

Translate -fglobal-isel to -plugin-opt=-global-isel=1.

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-driver

Author: Min-Yih Hsu (mshockwave)

Changes

Translate -fglobal-isel to -plugin-opt=-global-isel=1.

---

Full diff: https://github.com/llvm/llvm-project/pull/69747.diff

2 Files Affected:

• (modified) clang/lib/Driver/ToolChains/CommonArgs.cpp (+10)
• (modified) clang/test/Driver/lto.c (+9)

diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 7b2966f70bf6fc6..923fac940a00d3c 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -694,6 +694,16 @@ void tools::addLTOOptions(const ToolChain &ToolChain, const ArgList &Args,
     CmdArgs.push_back(Args.MakeArgString(Twine(PluginOptPrefix) +
                                          ParallelismOpt + Parallelism));
 
+  // Pass down GlobalISel options.
+  if (Arg *A = Args.getLastArg(options::OPT_fglobal_isel,
+                               options::OPT_fno_global_isel)) {
+    // Parsing -fno-global-isel explicitly gives architectures that enable GISel
+    // by default (e.g. AArch64) a chance to disable it.
+    CmdArgs.push_back(Args.MakeArgString(
+        Twine(PluginOptPrefix) + "-global-isel=" +
+        (A->getOption().matches(options::OPT_fglobal_isel) ? "1" : "0")));
+  }
+
   // If an explicit debugger tuning argument appeared, pass it along.
   if (Arg *A =
           Args.getLastArg(options::OPT_gTune_Group, options::OPT_ggdbN_Group)) {
diff --git a/clang/test/Driver/lto.c b/clang/test/Driver/lto.c
index 62bdbd6f5d3cfa3..b6c89eb99e27419 100644
--- a/clang/test/Driver/lto.c
+++ b/clang/test/Driver/lto.c
@@ -105,3 +105,12 @@
 // FLTO-THIN: -flto=thin
 // FLTO-THIN-NOT: "-flto"
 // FLTO-THIN-NOT: -flto=full
+
+// -flto passes along an explicit GlobalISel flag.
+// RUN: %clang --target=riscv64-linux-gnu -### %s -flto -fglobal-isel 2> %t
+// RUN: FileCheck --check-prefix=CHECK-GISEL < %t %s
+// RUN: %clang --target=aarch64-linux-gnu -### %s -flto -fno-global-isel 2> %t
+// RUN: FileCheck --check-prefix=CHECK-DISABLE-GISEL < %t %s
+//
+// CHECK-GISEL:         "-plugin-opt=-global-isel=1"
+// CHECK-DISABLE-GISEL: "-plugin-opt=-global-isel=0"

[MaskRay]

"e.g. AArch64" in "architectures that enable GISel by default (e.g. AArch64)" is not accurate. It's the default for -O0 and not for some code models. Perhaps just omit the "e.g." part.

[mshockwave]

Done