[OpenCL] Simplify LLVM IR generated for OpenCL blocks

Summary:
Emit direct call of block invoke functions when possible, i.e. in case the
block is not passed as a function argument.
Also doing some refactoring of `CodeGenFunction::EmitBlockCallExpr()`

Reviewers: Anastasia, yaxunl, svenvh

Reviewed By: Anastasia

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D58388

llvm-svn: 354568

1 files changed, 22 insertions, 8 deletions

diff --git a/clang/lib/CodeGen/CGOpenCLRuntime.cpp b/clang/lib/CodeGen/CGOpenCLRuntime.cpp
index 95732e93d5a..191a95c6299 100644
--- a/clang/lib/CodeGen/CGOpenCLRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenCLRuntime.cpp
@@ -122,6 +122,23 @@ llvm::PointerType *CGOpenCLRuntime::getGenericVoidPointerType() {
       CGM.getContext().getTargetAddressSpace(LangAS::opencl_generic));
 }
 
+// Get the block literal from an expression derived from the block expression.
+// OpenCL v2.0 s6.12.5:
+// Block variable declarations are implicitly qualified with const. Therefore
+// all block variables must be initialized at declaration time and may not be
+// reassigned.
+static const BlockExpr *getBlockExpr(const Expr *E) {
+  const Expr *Prev = nullptr; // to make sure we do not stuck in infinite loop.
+  while(!isa<BlockExpr>(E) && E != Prev) {
+    Prev = E;
+    E = E->IgnoreCasts();
+    if (auto DR = dyn_cast<DeclRefExpr>(E)) {
+      E = cast<VarDecl>(DR->getDecl())->getInit();
+    }
+  }
+  return cast<BlockExpr>(E);
+}
+
 /// Record emitted llvm invoke function and llvm block literal for the
 /// corresponding block expression.
 void CGOpenCLRuntime::recordBlockInfo(const BlockExpr *E,
@@ -136,20 +153,17 @@ void CGOpenCLRuntime::recordBlockInfo(const BlockExpr *E,
   EnqueuedBlockMap[E].Kernel = nullptr;
 }
 
+llvm::Function *CGOpenCLRuntime::getInvokeFunction(const Expr *E) {
+  return EnqueuedBlockMap[getBlockExpr(E)].InvokeFunc;
+}
+
 CGOpenCLRuntime::EnqueuedBlockInfo
 CGOpenCLRuntime::emitOpenCLEnqueuedBlock(CodeGenFunction &CGF, const Expr *E) {
   CGF.EmitScalarExpr(E);
 
   // The block literal may be assigned to a const variable. Chasing down
   // to get the block literal.
-  if (auto DR = dyn_cast<DeclRefExpr>(E)) {
-    E = cast<VarDecl>(DR->getDecl())->getInit();
-  }
-  E = E->IgnoreImplicit();
-  if (auto Cast = dyn_cast<CastExpr>(E)) {
-    E = Cast->getSubExpr();
-  }
-  auto *Block = cast<BlockExpr>(E);
+  const BlockExpr *Block = getBlockExpr(E);
 
   assert(EnqueuedBlockMap.find(Block) != EnqueuedBlockMap.end() &&
          "Block expression not emitted");