[Clang] Verify data layout consistency

Verify that the alignments specified by clang TargetInfo match
the alignments specified by LLVM data layout, which will hopefully
prevent accidental mismatches in the future.

This currently contains opt-outs for a lot of existing mismatches.

I'm also skipping the verification if options like `-malign-double`
are used, or a language that mandates sizes/alignments that differ
from C.

Author: nikic

clang/lib/CodeGen/CodeGenModule.cpp

@@ -332,6 +332,76 @@ const TargetCodeGenInfo &CodeGenModule::getTargetCodeGenInfo() {
   return *TheTargetCodeGenInfo;
 }
 
+static void checkDataLayoutConsistency(const TargetInfo &Target,
+                                       llvm::LLVMContext &Context,
+                                       const LangOptions &Opts) {
+#ifndef NDEBUG
+  // Don't verify non-standard ABI configurations.
+  if (Opts.AlignDouble || Opts.OpenCL || Opts.HLSL)
+    return;
+
+  llvm::Triple Triple = Target.getTriple();
+  llvm::DataLayout DL(Target.getDataLayoutString());
+  auto Check = [&](const char *Name, llvm::Type *Ty, unsigned Alignment) {
+    llvm::Align DLAlign = DL.getABITypeAlign(Ty);
+    llvm::Align ClangAlign(Alignment / 8);
+    if (DLAlign != ClangAlign) {
+      llvm::errs() << "For target " << Triple.str() << " type " << Name
+                   << " mapping to " << *Ty << " has data layout alignment "
+                   << DLAlign.value() << " while clang specifies "
+                   << ClangAlign.value() << "\n";
+      abort();
+    }
+  };
+
+  Check("bool", llvm::Type::getIntNTy(Context, Target.BoolWidth),
+        Target.BoolAlign);
+  Check("short", llvm::Type::getIntNTy(Context, Target.ShortWidth),
+        Target.ShortAlign);
+  // FIXME: M68k specifies incorrect wrong int and long alignments in Clang
+  // and incorrect long long alignment in both LLVM and Clang.
+  if (Triple.getArch() != llvm::Triple::m68k) {
+    Check("int", llvm::Type::getIntNTy(Context, Target.IntWidth),
+          Target.IntAlign);
+    Check("long", llvm::Type::getIntNTy(Context, Target.LongWidth),
+          Target.LongAlign);
+    Check("long long", llvm::Type::getIntNTy(Context, Target.LongLongWidth),
+          Target.LongLongAlign);
+  }
+  // FIXME: There are int128 alignment mismatches on multiple targets.
+  if (Target.hasInt128Type() && !Target.getTargetOpts().ForceEnableInt128 &&
+      !Triple.isAMDGPU() && !Triple.isSPIRV() &&
+      Triple.getArch() != llvm::Triple::ve)
+    Check("__int128", llvm::Type::getIntNTy(Context, 128), Target.Int128Align);
+
+  if (Target.hasFloat16Type())
+    Check("half", llvm::Type::getFloatingPointTy(Context, *Target.HalfFormat),
+          Target.HalfAlign);
+  if (Target.hasBFloat16Type())
+    Check("bfloat", llvm::Type::getBFloatTy(Context), Target.BFloat16Align);
+  Check("float", llvm::Type::getFloatingPointTy(Context, *Target.FloatFormat),
+        Target.FloatAlign);
+  // FIXME: AIX specifies wrong double alignment in DataLayout
+  if (!Triple.isOSAIX()) {
+    Check("double",
+          llvm::Type::getFloatingPointTy(Context, *Target.DoubleFormat),
+          Target.DoubleAlign);
+    Check("long double",
+          llvm::Type::getFloatingPointTy(Context, *Target.LongDoubleFormat),
+          Target.LongDoubleAlign);
+  }
+  // FIXME: Wasm has a mismatch in f128 alignment between Clang and LLVM.
+  if (Target.hasFloat128Type() && !Triple.isWasm())
+    Check("__float128", llvm::Type::getFP128Ty(Context), Target.Float128Align);
+  if (Target.hasIbm128Type())
+    Check("__ibm128", llvm::Type::getPPC_FP128Ty(Context), Target.Ibm128Align);
+
+  // FIXME: Clang specifies incorrect pointer alignment for m68k.
+  if (Triple.getArch() != llvm::Triple::m68k)
+    Check("void*", llvm::PointerType::getUnqual(Context), Target.PointerAlign);
+#endif
+}
+
 CodeGenModule::CodeGenModule(ASTContext &C,
                              IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS,
                              const HeaderSearchOptions &HSO,
@@ -487,6 +557,9 @@ CodeGenModule::CodeGenModule(ASTContext &C,
 
     llvm::sort(this->MSHotPatchFunctions);
   }
+
+  if (!Context.getAuxTargetInfo())
+    checkDataLayoutConsistency(Context.getTargetInfo(), LLVMContext, LangOpts);
 }
 
 CodeGenModule::~CodeGenModule() {}