Reland "[AArch64] handle -Wa,-march="

This reverts commit fd11a26d36, which was
reverted by 9145a3d4ab due to a test
failure on aarch64 backend, e.g.
https://lab.llvm.org/buildbot/#/builders/43/builds/7031. This patch
fixed the test failure.

Reviewed By: DavidSpickett, nickdesaulniers

Differential Revision: https://reviews.llvm.org/D103184

clang/lib/Driver/ToolChains/Arch/AArch64.cpp

@@ -185,12 +185,25 @@ getAArch64MicroArchFeaturesFromMcpu(const Driver &D, StringRef Mcpu,
 void aarch64::getAArch64TargetFeatures(const Driver &D,
                                        const llvm::Triple &Triple,
                                        const ArgList &Args,
-                                       std::vector<StringRef> &Features) {
+                                       std::vector<StringRef> &Features,
+                                       bool ForAS) {
   Arg *A;
   bool success = true;
   // Enable NEON by default.
   Features.push_back("+neon");
-  if ((A = Args.getLastArg(options::OPT_march_EQ)))
+  llvm::StringRef WaMArch = "";
+  if (ForAS)
+    for (const auto *A :
+         Args.filtered(options::OPT_Wa_COMMA, options::OPT_Xassembler))
+      for (StringRef Value : A->getValues())
+        if (Value.startswith("-march="))
+          WaMArch = Value.substr(7);
+  // Call getAArch64ArchFeaturesFromMarch only if "-Wa,-march=" or
+  // "-Xassembler -march" is detected. Otherwise it may return false
+  // and causes Clang to error out.
+  if (WaMArch.size())
+    success = getAArch64ArchFeaturesFromMarch(D, WaMArch, Args, Features);
+  else if ((A = Args.getLastArg(options::OPT_march_EQ)))
     success = getAArch64ArchFeaturesFromMarch(D, A->getValue(), Args, Features);
   else if ((A = Args.getLastArg(options::OPT_mcpu_EQ)))
     success = getAArch64ArchFeaturesFromMcpu(D, A->getValue(), Args, Features);

clang/lib/Driver/ToolChains/Arch/AArch64.h

@@ -22,7 +22,8 @@ namespace aarch64 {
 
 void getAArch64TargetFeatures(const Driver &D, const llvm::Triple &Triple,
                               const llvm::opt::ArgList &Args,
-                              std::vector<llvm::StringRef> &Features);
+                              std::vector<llvm::StringRef> &Features,
+                              bool ForAS);
 
 std::string getAArch64TargetCPU(const llvm::opt::ArgList &Args,
                                 const llvm::Triple &Triple, llvm::opt::Arg *&A);

clang/lib/Driver/ToolChains/Clang.cpp

@@ -344,7 +344,7 @@ static void getTargetFeatures(const Driver &D, const llvm::Triple &Triple,
   case llvm::Triple::aarch64:
   case llvm::Triple::aarch64_32:
   case llvm::Triple::aarch64_be:
-    aarch64::getAArch64TargetFeatures(D, Triple, Args, Features);
+    aarch64::getAArch64TargetFeatures(D, Triple, Args, Features, ForAS);
     break;
   case llvm::Triple::x86:
   case llvm::Triple::x86_64:

clang/test/Driver/aarch64-target-as-march.s

@@ -0,0 +1,46 @@
+/// These tests make sure that options passed to the assembler
+/// via -Wa or -Xassembler are applied correctly to assembler inputs.
+
+/// Does not apply to non assembly files
+// RUN: %clang --target=aarch64-linux-gnueabi -### -c -Wa,-march=armv8.1-a \
+// RUN: %S/Inputs/wildcard1.c 2>&1 | FileCheck --check-prefix=TARGET-FEATURE-1 %s
+// RUN: %clang --target=aarch64-linux-gnueabi -### -c -Xassembler -march=armv8.1-a \
+// RUN: %S/Inputs/wildcard1.c 2>&1 | FileCheck --check-prefix=TARGET-FEATURE-1 %s
+
+// TARGET-FEATURE-1-NOT: "-target-feature" "+v8.1a"
+
+/// Does apply to assembler input
+// RUN: %clang --target=aarch64-linux-gnueabi -### -c -Wa,-march=armv8.2-a %s 2>&1 | \
+// RUN: FileCheck --check-prefix=TARGET-FEATURE-2 %s
+// RUN: %clang --target=aarch64-linux-gnueabi -### -c -Xassembler -march=armv8.2-a %s 2>&1 | \
+// RUN: FileCheck --check-prefix=TARGET-FEATURE-2 %s
+
+// TARGET-FEATURE-2: "-target-feature" "+v8.2a"
+
+/// No unused argument warnings when there are multiple values
+// RUN: %clang --target=aarch64-linux-gnueabi -### -c -Wa,-march=armv8.1-a -Wa,-march=armv8.2-a %s 2>&1 | \
+// RUN: FileCheck --check-prefix=UNUSED-WARNING %s
+
+// UNUSED-WARNING-NOT: warning: argument unused during compilation
+
+/// Last march to assembler wins
+// RUN: %clang --target=aarch64-linux-gnueabi -### -c -Wa,-march=armv8.2-a -Wa,-march=armv8.1-a %s 2>&1 | \
+// RUN: FileCheck --check-prefix=MULTIPLE-VALUES %s
+// RUN: %clang --target=aarch64-linux-gnueabi -### -c -Wa,-march=armv8.2-a,-march=armv8.1-a %s 2>&1 | \
+// RUN: FileCheck --check-prefix=MULTIPLE-VALUES %s
+// RUN: %clang --target=aarch64-linux-gnueabi -### -c -Xassembler -march=armv8.2-a -Xassembler \
+// RUN: -march=armv8.1-a %s 2>&1 | FileCheck --check-prefix=MULTIPLE-VALUES %s
+
+// MULTIPLE-VALUES: "-target-feature" "+v8.1a
+// MULTIPLE-VALUES-NOT: "-target-feature" "+v8.2a
+
+/// march to compiler and assembler, we choose the one suited to the input file type
+// RUN: %clang --target=aarch64-linux-gnueabi -### -c -Wa,-march=armv8.3-a -march=armv8.4-a %s 2>&1 | \
+// RUN: FileCheck --check-prefix=TARGET-FEATURE-3 %s
+// RUN: %clang --target=aarch64-linux-gnueabi -### -c -Wa,-march=armv8.3-a -march=armv8.4-a \
+// RUN: %S/Inputs/wildcard1.c 2>&1 | FileCheck --check-prefix=TARGET-FEATURE-4 %s
+
+// TARGET-FEATURE-3: "-target-feature" "+v8.3a"
+// TARGET-FEATURE-3-NOT: "-target-feature" "+v8.4a"
+// TARGET-FEATURE-4: "-target-feature" "+v8.4a"
+// TARGET-FEATURE-4-NOT: "-target-feature" "+v8.3a"