[clang] [clang][AArch64] multilib: fix deduction of "-march=" option (PR #81474)

[Dominik Wójt via cfe-commits]

https://github.com/domin144 updated https://github.com/llvm/llvm-project/pull/81474

>From da3ef3a5705ca4eec5683e0c048dd93da8c58b5d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dominik=20W=C3=B3jt?= <dominik.wojt at arm.com>
Date: Mon, 12 Feb 2024 13:38:14 +0100
Subject: [PATCH 1/3] [clang][AArch64] multilib: fix deduction of "-march="
 option

The deduced "-march=" option always started with aarch64, which is not a
valid value. There was also no way to distinguish between armv8-r and
armv8-a. After this commit, the deduced "-march=" option will start with
greatest available "armv*-a" value or "armv8-r".
---
 clang/lib/Driver/ToolChain.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp
index 657577cea6c7d8..623d52e9471f23 100644
--- a/clang/lib/Driver/ToolChain.cpp
+++ b/clang/lib/Driver/ToolChain.cpp
@@ -191,7 +191,11 @@ static void getAArch64MultilibFlags(const Driver &D,
   for (const auto &Ext : AArch64::Extensions)
     if (FeatureSet.contains(Ext.NegFeature))
       MArch.push_back(("no" + Ext.Name).str());
-  MArch.insert(MArch.begin(), ("-march=" + Triple.getArchName()).str());
+  StringRef ArchName;
+  for (const auto &ArchInfo : AArch64::ArchInfos)
+    if (FeatureSet.contains(ArchInfo->ArchFeature))
+      ArchName = ArchInfo->Name;
+  MArch.insert(MArch.begin(), ("-march=" + ArchName).str());
   Result.push_back(llvm::join(MArch, "+"));
 }
 

>From 9617abcb6e911a1c6d44b9e5a6bb161e17a0f267 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dominik=20W=C3=B3jt?= <dominik.wojt at arm.com>
Date: Mon, 12 Feb 2024 14:46:26 +0100
Subject: [PATCH 2/3] fix tests

---
 clang/test/Driver/print-multi-selection-flags.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/clang/test/Driver/print-multi-selection-flags.c b/clang/test/Driver/print-multi-selection-flags.c
index 248d9a3cdf49b2..06a12db9d97792 100644
--- a/clang/test/Driver/print-multi-selection-flags.c
+++ b/clang/test/Driver/print-multi-selection-flags.c
@@ -51,9 +51,10 @@
 // CHECK-M85_NO_FP_DP: -mfpu=fp-armv8-fullfp16-sp-d16
 
 // RUN: %clang -print-multi-flags-experimental --target=aarch64-none-elf -march=armv8-a+lse | FileCheck --check-prefix=CHECK-LSE %s
-// CHECK-LSE: -march=aarch64{{.*}}+lse{{.*}}
+// CHECK-LSE: --target=aarch64-none-unknown-elf
+// CHECK-LSE: -march=armv8-a{{.*}}+lse{{.*}}
 
 // RUN: %clang -print-multi-flags-experimental --target=aarch64-none-elf -march=armv8.5-a+sve+sve2 | FileCheck --check-prefix=CHECK-SVE2 %s
 // RUN: %clang -print-multi-flags-experimental --target=aarch64-none-elf -march=armv9-a            | FileCheck --check-prefix=CHECK-SVE2 %s
 // CHECK-SVE2: --target=aarch64-none-unknown-elf
-// CHECK-SVE2: -march=aarch64{{.*}}+simd{{.*}}+sve{{.*}}+sve2{{.*}}
+// CHECK-SVE2: -march=armv{{.*}}-a{{.*}}+simd{{.*}}+sve{{.*}}+sve2{{.*}}

>From b7da6a6eeae688ba5ac03d51d6cc34c2dea798b1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dominik=20W=C3=B3jt?= <dominik.wojt at arm.com>
Date: Thu, 15 Feb 2024 12:55:11 +0100
Subject: [PATCH 3/3] add assert for missing arch feature

---
 clang/lib/Driver/ToolChain.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp
index 623d52e9471f23..0415e37f2e32f0 100644
--- a/clang/lib/Driver/ToolChain.cpp
+++ b/clang/lib/Driver/ToolChain.cpp
@@ -195,6 +195,7 @@ static void getAArch64MultilibFlags(const Driver &D,
   for (const auto &ArchInfo : AArch64::ArchInfos)
     if (FeatureSet.contains(ArchInfo->ArchFeature))
       ArchName = ArchInfo->Name;
+  assert(!ArchName.empty() && "at least one architecture should be found");
   MArch.insert(MArch.begin(), ("-march=" + ArchName).str());
   Result.push_back(llvm::join(MArch, "+"));
 }