r314145 - Reinstall the patch "Use EmitPointerWithAlignment to get alignment information of the pointer used in atomic expr" after fixing PR31620.

[Wei Mi via cfe-commits]

Author: wmi
Date: Mon Sep 25 12:57:59 2017
New Revision: 314145

URL: http://llvm.org/viewvc/llvm-project?rev=314145&view=rev
Log:
Reinstall the patch "Use EmitPointerWithAlignment to get alignment information of the pointer used in atomic expr" after fixing PR31620.

This is to fix PR34347. EmitAtomicExpr now only uses alignment information from
Type, instead of Decl, so when the declaration of an atomic variable is marked
to have the alignment equal as its size, EmitAtomicExpr doesn't know about it and
will generate libcall instead of atomic op. The patch uses EmitPointerWithAlignment
to get the precise alignment information.

Differential Revision: https://reviews.llvm.org/D37310

Added:
    cfe/trunk/test/CodeGenCXX/atomic-align.cpp
Modified:
    cfe/trunk/lib/CodeGen/CGAtomic.cpp

Modified: cfe/trunk/lib/CodeGen/CGAtomic.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGAtomic.cpp?rev=314145&r1=314144&r2=314145&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGAtomic.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGAtomic.cpp Mon Sep 25 12:57:59 2017
@@ -745,19 +745,19 @@ RValue CodeGenFunction::EmitAtomicExpr(A
   QualType MemTy = AtomicTy;
   if (const AtomicType *AT = AtomicTy->getAs<AtomicType>())
     MemTy = AT->getValueType();
-  CharUnits sizeChars, alignChars;
-  std::tie(sizeChars, alignChars) = getContext().getTypeInfoInChars(AtomicTy);
-  uint64_t Size = sizeChars.getQuantity();
-  unsigned MaxInlineWidthInBits = getTarget().getMaxAtomicInlineWidth();
-  bool UseLibcall = (sizeChars != alignChars ||
-                     getContext().toBits(sizeChars) > MaxInlineWidthInBits);
-
   llvm::Value *IsWeak = nullptr, *OrderFail = nullptr;
 
   Address Val1 = Address::invalid();
   Address Val2 = Address::invalid();
   Address Dest = Address::invalid();
-  Address Ptr(EmitScalarExpr(E->getPtr()), alignChars);
+  Address Ptr = EmitPointerWithAlignment(E->getPtr());
+
+  CharUnits sizeChars, alignChars;
+  std::tie(sizeChars, alignChars) = getContext().getTypeInfoInChars(AtomicTy);
+  uint64_t Size = sizeChars.getQuantity();
+  unsigned MaxInlineWidthInBits = getTarget().getMaxAtomicInlineWidth();
+  bool UseLibcall = ((Ptr.getAlignment() % sizeChars) != 0 ||
+                     getContext().toBits(sizeChars) > MaxInlineWidthInBits);
 
   if (E->getOp() == AtomicExpr::AO__c11_atomic_init ||
       E->getOp() == AtomicExpr::AO__opencl_atomic_init) {

Added: cfe/trunk/test/CodeGenCXX/atomic-align.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/atomic-align.cpp?rev=314145&view=auto
==============================================================================
--- cfe/trunk/test/CodeGenCXX/atomic-align.cpp (added)
+++ cfe/trunk/test/CodeGenCXX/atomic-align.cpp Mon Sep 25 12:57:59 2017
@@ -0,0 +1,30 @@
+// RUN: %clang_cc1 %s -std=c++11 -emit-llvm -o - -triple=x86_64-linux-gnu | FileCheck %s
+
+struct AM {
+  int f1, f2;
+};
+alignas(8) AM m;
+AM load1() {
+  AM am;
+  // m is declared to align to 8bytes, so generate load atomic instead
+  // of libcall.
+  // CHECK-LABEL: @_Z5load1v
+  // CHECK: load atomic {{.*}} monotonic
+  __atomic_load(&m, &am, 0);
+  return am;
+}
+
+struct BM {
+  int f1;
+  alignas(8) AM f2;
+};
+BM bm;
+AM load2() {
+  AM am;
+  // BM::f2 is declared to align to 8bytes, so generate load atomic instead
+  // of libcall.
+  // CHECK-LABEL: @_Z5load2v
+  // CHECK: load atomic {{.*}} monotonic
+  __atomic_load(&bm.f2, &am, 0);
+  return am;
+}