[X86] Prevent passing vectors of __int128 as <X x i128> in llvm IR

As far as I can tell, gcc passes 256/512 bit vectors __int128 in memory. And passes a vector of 1 _int128 in an xmm register. The backend considers <X x i128> as an illegal type and will scalarize any arguments with that type. So we need to coerce the argument types in the frontend to match to avoid the illegal type.

I'm restricting this to change to Linux and NetBSD based on the
how similar ABI changes have been handled in the past.
PS4, FreeBSD, and Darwin are unaffected. I've also added a
new -fclang-abi-compat version to restore the old behavior.

This issue was identified in PR42607. Though even with the types changed, we still seem to be doing some unnecessary stack realignment.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@371169 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 42 insertions, 2 deletions

diff --git a/lib/CodeGen/TargetInfo.cpp b/lib/CodeGen/TargetInfo.cpp
index ffd5586337..f2696a33cf 100644
--- a/lib/CodeGen/TargetInfo.cpp
+++ b/lib/CodeGen/TargetInfo.cpp
@@ -2180,6 +2180,17 @@ class X86_64ABIInfo : public SwiftABIInfo {
     return true;
   }
 
+  // GCC classifies vectors of __int128 as memory.
+  bool passInt128VectorsInMem() const {
+    // Clang <= 9.0 did not do this.
+    if (getContext().getLangOpts().getClangABICompat() <=
+        LangOptions::ClangABI::Ver9)
+      return false;
+
+    const llvm::Triple &T = getTarget().getTriple();
+    return T.isOSLinux() || T.isOSNetBSD();
+  }
+
   X86AVXABILevel AVXLevel;
   // Some ABIs (e.g. X32 ABI and Native Client OS) use 32 bit pointers on
   // 64-bit hardware.
@@ -2660,6 +2671,14 @@ void X86_64ABIInfo::classify(QualType Ty, uint64_t OffsetBase,
         Hi = Lo;
     } else if (Size == 128 ||
                (isNamedArg && Size <= getNativeVectorSizeForAVXABI(AVXLevel))) {
+      QualType ElementType = VT->getElementType();
+
+      // gcc passes 256 and 512 bit <X x __int128> vectors in memory. :(
+      if (passInt128VectorsInMem() && Size != 128 &&
+          (ElementType->isSpecificBuiltinType(BuiltinType::Int128) ||
+           ElementType->isSpecificBuiltinType(BuiltinType::UInt128)))
+        return;
+
       // Arguments of 256-bits are split into four eightbyte chunks. The
       // least significant one belongs to class SSE and all the others to class
       // SSEUP. The original Lo and Hi design considers that types can't be
@@ -2902,6 +2921,11 @@ bool X86_64ABIInfo::IsIllegalVectorType(QualType Ty) const {
     unsigned LargestVector = getNativeVectorSizeForAVXABI(AVXLevel);
     if (Size <= 64 || Size > LargestVector)
       return true;
+    QualType EltTy = VecTy->getElementType();
+    if (passInt128VectorsInMem() &&
+        (EltTy->isSpecificBuiltinType(BuiltinType::Int128) ||
+         EltTy->isSpecificBuiltinType(BuiltinType::UInt128)))
+      return true;
   }
 
   return false;
@@ -2976,14 +3000,28 @@ llvm::Type *X86_64ABIInfo::GetByteVectorType(QualType Ty) const {
     Ty = QualType(InnerTy, 0);
 
   llvm::Type *IRType = CGT.ConvertType(Ty);
-  if (isa<llvm::VectorType>(IRType) ||
-      IRType->getTypeID() == llvm::Type::FP128TyID)
+  if (isa<llvm::VectorType>(IRType)) {
+    // Don't pass vXi128 vectors in their native type, the backend can't
+    // legalize them.
+    if (passInt128VectorsInMem() &&
+        IRType->getVectorElementType()->isIntegerTy(128)) {
+      // Use a vXi64 vector.
+      uint64_t Size = getContext().getTypeSize(Ty);
+      return llvm::VectorType::get(llvm::Type::getInt64Ty(getVMContext()),
+                                   Size / 64);
+    }
+
+    return IRType;
+  }
+
+  if (IRType->getTypeID() == llvm::Type::FP128TyID)
     return IRType;
 
   // We couldn't find the preferred IR vector type for 'Ty'.
   uint64_t Size = getContext().getTypeSize(Ty);
   assert((Size == 128 || Size == 256 || Size == 512) && "Invalid type found!");
 
+
   // Return a LLVM IR vector type based on the size of 'Ty'.
   return llvm::VectorType::get(llvm::Type::getDoubleTy(getVMContext()),
                                Size / 64);
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 711f7dfa65..f1624532f8 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -3164,6 +3164,8 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
         Opts.setClangABICompat(LangOptions::ClangABI::Ver6);
       else if (Major <= 7)
         Opts.setClangABICompat(LangOptions::ClangABI::Ver7);
+      else if (Major <= 9)
+        Opts.setClangABICompat(LangOptions::ClangABI::Ver9);
     } else if (Ver != "latest") {
       Diags.Report(diag::err_drv_invalid_value)
           << A->getAsString(Args) << A->getValue();