[OpenMP] Update target directive codegen to use 4.5 implicit data mappings.

Summary:
This patch implements the 4.5 specification for the implicit data maps. OpenMP 4.5 specification changes the default way data is captured into a target region. All the non-aggregate kinds are passed by value by default. This required activating the capturing by value during SEMA for the target region. All the non-aggregate values that can be encoded in the size of a pointer are properly casted and forwarded to the runtime library. On top of fixing the previous weird behavior for mapping pointers in nested data regions (an explicit map was always required), this also improves performance as the number of allocations/transactions to the device per non-aggregate map are reduced from two to only one - instead of passing a reference and the value, only the value passed.

Explicit maps will be added later on once firstprivate, private, and map clauses' SEMA and parsing are available.

Reviewers: hfinkel, rjmccall, ABataev

Subscribers: cfe-commits, carlo.bertolli

Differential Revision: http://reviews.llvm.org/D14940

llvm-svn: 254521

1 files changed, 18 insertions, 5 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 3481f73e693..6ec5fe2e2fd 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -12621,10 +12621,15 @@ static bool isVariableAlreadyCapturedInScopeInfo(CapturingScopeInfo *CSI, VarDec
       
     // Compute the type of an expression that refers to this variable.
     DeclRefType = CaptureType.getNonReferenceType();
-      
+
+    // Similarly to mutable captures in lambda, all the OpenMP captures by copy
+    // are mutable in the sense that user can change their value - they are
+    // private instances of the captured declarations.
     const CapturingScopeInfo::Capture &Cap = CSI->getCapture(Var);
     if (Cap.isCopyCapture() &&
-        !(isa<LambdaScopeInfo>(CSI) && cast<LambdaScopeInfo>(CSI)->Mutable))
+        !(isa<LambdaScopeInfo>(CSI) && cast<LambdaScopeInfo>(CSI)->Mutable) &&
+        !(isa<CapturedRegionScopeInfo>(CSI) &&
+          cast<CapturedRegionScopeInfo>(CSI)->CapRegionKind == CR_OpenMP))
       DeclRefType.addConst();
     return true;
   }
@@ -12812,9 +12817,17 @@ static bool captureInCapturedRegion(CapturedRegionScopeInfo *RSI,
   // By default, capture variables by reference.
   bool ByRef = true;
   // Using an LValue reference type is consistent with Lambdas (see below).
-  if (S.getLangOpts().OpenMP && S.IsOpenMPCapturedVar(Var))
-    DeclRefType = DeclRefType.getUnqualifiedType();
-  CaptureType = S.Context.getLValueReferenceType(DeclRefType);
+  if (S.getLangOpts().OpenMP) {
+    ByRef = S.IsOpenMPCapturedByRef(Var, RSI);
+    if (S.IsOpenMPCapturedVar(Var))
+      DeclRefType = DeclRefType.getUnqualifiedType();
+  }
+
+  if (ByRef)
+    CaptureType = S.Context.getLValueReferenceType(DeclRefType);
+  else
+    CaptureType = DeclRefType;
+
   Expr *CopyExpr = nullptr;
   if (BuildAndDiagnose) {
     // The current implementation assumes that all variables are captured