[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

Author: mstorsjo

clang/include/clang/Basic/BuiltinsARM.def

@@ -115,6 +115,14 @@ LANGBUILTIN(__sevl, "v", "", ALL_MS_LANGUAGES)
 LANGBUILTIN(__dmb, "vUi", "nc", ALL_MS_LANGUAGES)
 LANGBUILTIN(__dsb, "vUi", "nc", ALL_MS_LANGUAGES)
 LANGBUILTIN(__isb, "vUi", "nc", ALL_MS_LANGUAGES)
+LANGBUILTIN(__iso_volatile_load8,   "ccCD*",     "n", ALL_MS_LANGUAGES)
+LANGBUILTIN(__iso_volatile_load16,  "ssCD*",     "n", ALL_MS_LANGUAGES)
+LANGBUILTIN(__iso_volatile_load32,  "iiCD*",     "n", ALL_MS_LANGUAGES)
+LANGBUILTIN(__iso_volatile_load64,  "LLiLLiCD*", "n", ALL_MS_LANGUAGES)
+LANGBUILTIN(__iso_volatile_store8,  "vcD*c",     "n", ALL_MS_LANGUAGES)
+LANGBUILTIN(__iso_volatile_store16, "vsD*s",     "n", ALL_MS_LANGUAGES)
+LANGBUILTIN(__iso_volatile_store32, "viD*i",     "n", ALL_MS_LANGUAGES)
+LANGBUILTIN(__iso_volatile_store64, "vLLiD*LLi", "n", ALL_MS_LANGUAGES)
 LANGBUILTIN(__ldrexd, "WiWiCD*", "", ALL_MS_LANGUAGES)
 LANGBUILTIN(_MoveFromCoprocessor, "UiIUiIUiIUiIUiIUi", "", ALL_MS_LANGUAGES)
 LANGBUILTIN(_MoveFromCoprocessor2, "UiIUiIUiIUiIUiIUi", "", ALL_MS_LANGUAGES)

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);

clang/test/CodeGen/ms-volatile-arm.c

@@ -0,0 +1,13 @@
+// REQUIRES: arm-registered-target
+// RUN: %clang_cc1 -triple thumbv7-win32 -emit-llvm -fms-extensions -fms-volatile -o - < %s | FileCheck %s
+
+void test1(int volatile *p, int v) {
+  __iso_volatile_store32(p, v);
+  // CHECK-LABEL: @test1
+  // CHECK: store volatile {{.*}}, {{.*}}
+}
+int test2(const int volatile *p) {
+  return __iso_volatile_load32(p);
+  // CHECK-LABEL: @test2
+  // CHECK: load volatile {{.*}}
+}