[MS] Implement __iso_volatile loads/stores as builtins

These are supposed to produce the same as normal volatile
pointer loads/stores. When -volatile:ms is specified,
normal volatile pointers are forced to have atomic semantics
(as is the default on x86 in MSVC mode). In that case,
these builtins should still produce non-atomic volatile
loads/stores without acquire/release semantics, which
the new test verifies.

These are only available on ARM (and on AArch64,
although clang doesn't support AArch64/Windows yet).

This implements what is missing for PR30394, making it possible
to compile C++ for ARM in MSVC mode with MSVC headers.

Differential Revision: https://reviews.llvm.org/D24986

llvm-svn: 282900

1 files changed, 35 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 2f4fbcff253..8ce69b8921e 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -4279,6 +4279,41 @@ Value *CodeGenFunction::EmitARMBuiltinExpr(unsigned BuiltinID,
     return Builder.CreateCall(F, {StoreVal, StoreAddr}, "strex");
   }
 
+  switch (BuiltinID) {
+  case ARM::BI__iso_volatile_load8:
+  case ARM::BI__iso_volatile_load16:
+  case ARM::BI__iso_volatile_load32:
+  case ARM::BI__iso_volatile_load64: {
+    Value *Ptr = EmitScalarExpr(E->getArg(0));
+    QualType ElTy = E->getArg(0)->getType()->getPointeeType();
+    CharUnits LoadSize = getContext().getTypeSizeInChars(ElTy);
+    llvm::Type *ITy = llvm::IntegerType::get(getLLVMContext(),
+                                             LoadSize.getQuantity() * 8);
+    Ptr = Builder.CreateBitCast(Ptr, ITy->getPointerTo());
+    llvm::LoadInst *Load =
+      Builder.CreateAlignedLoad(Ptr, LoadSize);
+    Load->setVolatile(true);
+    return Load;
+  }
+  case ARM::BI__iso_volatile_store8:
+  case ARM::BI__iso_volatile_store16:
+  case ARM::BI__iso_volatile_store32:
+  case ARM::BI__iso_volatile_store64: {
+    Value *Ptr = EmitScalarExpr(E->getArg(0));
+    Value *Value = EmitScalarExpr(E->getArg(1));
+    QualType ElTy = E->getArg(0)->getType()->getPointeeType();
+    CharUnits StoreSize = getContext().getTypeSizeInChars(ElTy);
+    llvm::Type *ITy = llvm::IntegerType::get(getLLVMContext(),
+                                             StoreSize.getQuantity() * 8);
+    Ptr = Builder.CreateBitCast(Ptr, ITy->getPointerTo());
+    llvm::StoreInst *Store =
+      Builder.CreateAlignedStore(Value, Ptr,
+                                 StoreSize);
+    Store->setVolatile(true);
+    return Store;
+  }
+  }
+
   if (BuiltinID == ARM::BI__builtin_arm_clrex) {
     Function *F = CGM.getIntrinsic(Intrinsic::arm_clrex);
     return Builder.CreateCall(F);