[clang] [clang] Add fbasic-block-sections support for AArch64 (PR #80916)

[Daniel Hoekwater via cfe-commits]

https://github.com/dhoekwater updated https://github.com/llvm/llvm-project/pull/80916

>From 36f9de4ab82f4f27131f561417749481eada0f3e Mon Sep 17 00:00:00 2001
From: Daniel Hoekwater <hoekwater at google.com>
Date: Wed, 7 Feb 2024 01:03:17 +0000
Subject: [PATCH] [Driver] Allow -fbasic-block-sections for AArch64 ELF

Basic block sections "all" doesn't work on AArch64 since branch
relaxation may create new basic blocks. However, the other basic
block section modes should work out of the box since machine function
splitting already uses the basic block sections pass.
---
 clang/lib/Driver/ToolChains/Clang.cpp     | 9 +++++++++
 clang/test/Driver/fbasic-block-sections.c | 4 ++++
 2 files changed, 13 insertions(+)

diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 13bf242115437..b970533ddc253 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5972,6 +5972,15 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
             << A->getAsString(Args) << A->getValue();
       else
         A->render(Args, CmdArgs);
+    } else if (Triple.isAArch64() && Triple.isOSBinFormatELF) {
+      // "all" is not supported on AArch64 since branch relaxation creates new
+      // basic blocks for some cross-section branches.
+      if (Val != "labels" && Val != "none" && !Val.starts_with("list="))
+        D.Diag(diag::err_drv_invalid_value)
+            << A->getAsString(Args) << A->getValue();
+      else
+        A->render(Args, CmdArgs);
+    }
     } else if (Triple.isNVPTX()) {
       // Do not pass the option to the GPU compilation. We still want it enabled
       // for the host-side compilation, so seeing it here is not an error.
diff --git a/clang/test/Driver/fbasic-block-sections.c b/clang/test/Driver/fbasic-block-sections.c
index 24262209d1e4d..5e701072bfc74 100644
--- a/clang/test/Driver/fbasic-block-sections.c
+++ b/clang/test/Driver/fbasic-block-sections.c
@@ -2,6 +2,10 @@
 // RUN: %clang -### --target=x86_64 -fbasic-block-sections=all %s -S 2>&1 | FileCheck -check-prefix=CHECK-OPT-ALL %s
 // RUN: %clang -### --target=x86_64 -fbasic-block-sections=list=%s %s -S 2>&1 | FileCheck -check-prefix=CHECK-OPT-LIST %s
 // RUN: %clang -### --target=x86_64 -fbasic-block-sections=labels %s -S 2>&1 | FileCheck -check-prefix=CHECK-OPT-LABELS %s
+// RUN: %clang -### --target=aarch64 -fbasic-block-sections=none %s -S 2>&1 | FileCheck -check-prefix=CHECK-OPT-NONE %s
+// RUN: %clang -### --target=aarch64 -fbasic-block-sections=list=%s %s -S 2>&1 | FileCheck -check-prefix=CHECK-OPT-LIST %s
+// RUN: %clang -### --target=aarch64 -fbasic-block-sections=labels %s -S 2>&1 | FileCheck -check-prefix=CHECK-OPT-LABELS %s
+// RUN: not %clang -### --target=aarch64 -fbasic-block-sections=all %s -S 2>&1 | FileCheck -check-prefix=CHECK-OPT-ALL %s
 // RUN: not %clang -c --target=arm-unknown-linux -fbasic-block-sections=all %s -S 2>&1 | FileCheck -check-prefix=CHECK-TRIPLE %s
 // RUN: %clang -### --target=arm-unknown-linux -fbasic-block-sections=all -fbasic-block-sections=none %s -S 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHECK-NOOPT %s