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

[jcai19]

Summary

This relands commit fd11a26d368c5a909fb88548fef2cee7a6c2c931, which was
reverted by 9145a3d4ab7eb05d9fb113b5392e8961df629b88 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.

[nickdesaulniers]

This reverts commit fd11a26d368c5a909fb88548fef2cee7a6c2c931

Shouldn't that be This relands commit fd11a26d368c5a909fb88548fef2cee7a6c2c931?

It's pretty hard to see what's different in this new version since the original, can you comment on how you fixed the issue?

[jcai19]

Add comments explaning the difference with D103184. The implementation in D103184 unconditionally calls getAArch64ArchFeaturesFromMarch, which returns false when an irrelevant -Wa value is detected and parsed (e.g. -Wa,--version) and causes Clang to bail out.

[jcai19]

In D104656#2831034, @nickdesaulniers wrote:

This reverts commit fd11a26d368c5a909fb88548fef2cee7a6c2c931

Shouldn't that be This relands commit fd11a26d368c5a909fb88548fef2cee7a6c2c931?

Done. Thanks for noticing the typo.

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

 
 namespace clang {
 namespace driver {
 namespace tools {
 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);
 
 } // end namespace aarch64
 } // end namespace target
 } // end namespace driver
 } // end namespace clang
 
 #endif // LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_ARCH_AARCH64_H

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

if (!DecodeAArch64Mcpu(D, McpuLowerCase, CPU, DecodedFeature))
     return false;
 
   return getAArch64MicroArchFeaturesFromMtune(D, CPU, Args, Features);
 }
 
 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);
   else if (Args.hasArg(options::OPT_arch) || isCPUDeterminedByTriple(Triple))
     success = getAArch64ArchFeaturesFromMcpu(
         D, getAArch64TargetCPU(Args, Triple, A), Args, Features);
 
   if (success && (A = Args.getLastArg(clang::driver::options::OPT_mtune_EQ)))

clang/lib/Driver/ToolChains/Clang.cpp

case llvm::Triple::riscv64:
     riscv::getRISCVTargetFeatures(D, Triple, Args, Features);
     break;
   case llvm::Triple::systemz:
     systemz::getSystemZTargetFeatures(D, Args, Features);
     break;
   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:
     x86::getX86TargetFeatures(D, Triple, Args, Features);
     break;
   case llvm::Triple::hexagon:
     hexagon::getHexagonTargetFeatures(D, Args, Features);
     break;

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

+/// 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"