Simplify codegen and debug info generation for block context parameters.

The exisiting code goes out of its way to put block parameters into an
alloca only at -O0, and then describes the funciton argument with a
dbg.declare, which is undocumented in the LLVM-CFE contract and does
not actually behave as intended after LLVM r642022.

This patch just generates the alloca unconditionally, the mem2reg pass
will eliminate it at -O1 and up anyway and points the dbg.declare to
the alloca as intended (which mem2reg will then correctly rewrite into
a dbg.value).

This reapplies r316684 with some dead code removed.

rdar://problem/35043980

Differential Revision: https://reviews.llvm.org/D39305

llvm-svn: 316689

1 files changed, 7 insertions, 10 deletions

diff --git a/clang/lib/CodeGen/CGBlocks.cpp b/clang/lib/CodeGen/CGBlocks.cpp
index 2915dabe541..0bd9d7c506c 100644
--- a/clang/lib/CodeGen/CGBlocks.cpp
+++ b/clang/lib/CodeGen/CGBlocks.cpp
@@ -1293,20 +1293,17 @@ void CodeGenFunction::setBlockContextParameter(const ImplicitParamDecl *D,
                                                llvm::Value *arg) {
   assert(BlockInfo && "not emitting prologue of block invocation function?!");
 
-  llvm::Value *localAddr = nullptr;
-  if (CGM.getCodeGenOpts().OptimizationLevel == 0) {
-    // Allocate a stack slot to let the debug info survive the RA.
-    Address alloc = CreateMemTemp(D->getType(), D->getName() + ".addr");
-    Builder.CreateStore(arg, alloc);
-    localAddr = Builder.CreateLoad(alloc);
-  }
-
+  // Allocate a stack slot like for any local variable to guarantee optimal
+  // debug info at -O0. The mem2reg pass will eliminate it when optimizing.
+  Address alloc = CreateMemTemp(D->getType(), D->getName() + ".addr");
+  Builder.CreateStore(arg, alloc);
   if (CGDebugInfo *DI = getDebugInfo()) {
     if (CGM.getCodeGenOpts().getDebugInfo() >=
         codegenoptions::LimitedDebugInfo) {
       DI->setLocation(D->getLocation());
-      DI->EmitDeclareOfBlockLiteralArgVariable(*BlockInfo, arg, argNum,
-                                               localAddr, Builder);
+      DI->EmitDeclareOfBlockLiteralArgVariable(
+          *BlockInfo, D->getName(), argNum,
+          cast<llvm::AllocaInst>(alloc.getPointer()), Builder);
     }
   }