[IRGen] Emit lifetime markers for temporary struct allocas

When passing arguments using temporary allocas, we need to add the
appropriate lifetime markers so that the stack coloring passes can
re-use the stack space.

This patch keeps track of all the lifetime.start calls emited before the
codegened call, and adds the corresponding lifetime.end calls after the
call.

Differential Revision: https://reviews.llvm.org/D68611

llvm-svn: 374126

1 files changed, 22 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index b016b46acfe..682a7ccb493 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -3878,6 +3878,11 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
   Address swiftErrorTemp = Address::invalid();
   Address swiftErrorArg = Address::invalid();
 
+  // When passing arguments using temporary allocas, we need to add the
+  // appropriate lifetime markers. This vector keeps track of all the lifetime
+  // markers that need to be ended right after the call.
+  SmallVector<CallLifetimeEnd, 2> CallLifetimeEndAfterCall;
+
   // Translate all of the arguments as necessary to match the IR lowering.
   assert(CallInfo.arg_size() == CallArgs.size() &&
          "Mismatch between function signature & arguments.");
@@ -3994,6 +3999,18 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
           Address AI = CreateMemTempWithoutCast(
               I->Ty, ArgInfo.getIndirectAlign(), "byval-temp");
           IRCallArgs[FirstIRArg] = AI.getPointer();
+
+          // Emit lifetime markers for the temporary alloca.
+          uint64_t ByvalTempElementSize =
+              CGM.getDataLayout().getTypeAllocSize(AI.getElementType());
+          llvm::Value *LifetimeSize =
+              EmitLifetimeStart(ByvalTempElementSize, AI.getPointer());
+
+          // Add cleanup code to emit the end lifetime marker after the call.
+          if (LifetimeSize) // In case we disabled lifetime markers.
+            CallLifetimeEndAfterCall.emplace_back(AI, LifetimeSize);
+
+          // Generate the copy.
           I->copyInto(*this, AI);
         } else {
           // Skip the extra memcpy call.
@@ -4562,6 +4579,11 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
     }
   }
 
+  // Explicitly call CallLifetimeEnd::Emit just to re-use the code even though
+  // we can't use the full cleanup mechanism.
+  for (CallLifetimeEnd &LifetimeEnd : CallLifetimeEndAfterCall)
+    LifetimeEnd.Emit(*this, /*Flags=*/{});
+
   return Ret;
 }