Try to implement lambdas with inalloca parameters by forwarding without use of inallocas.

Differential Revision: https://reviews.llvm.org/D137872

1 files changed, 24 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index b8d3937..6899388 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -683,6 +683,19 @@ static bool matchesStlAllocatorFn(const Decl *D, const ASTContext &Ctx) {
   return true;
 }
 
+bool CodeGenFunction::isInAllocaArgument(CGCXXABI &ABI, QualType Ty) {
+  const CXXRecordDecl *RD = Ty->getAsCXXRecordDecl();
+  return RD && ABI.getRecordArgABI(RD) == CGCXXABI::RAA_DirectInMemory;
+}
+
+bool CodeGenFunction::hasInAllocaArg(const CXXMethodDecl *MD) {
+  return getTarget().getTriple().getArch() == llvm::Triple::x86 &&
+         getTarget().getCXXABI().isMicrosoft() &&
+         llvm::any_of(MD->parameters(), [&](ParmVarDecl *P) {
+           return isInAllocaArgument(CGM.getCXXABI(), P->getType());
+         });
+}
+
 /// Return the UBSan prologue signature for \p FD if one is available.
 static llvm::Constant *getPrologueSignature(CodeGenModule &CGM,
                                             const FunctionDecl *FD) {
@@ -1447,6 +1460,17 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn,
     // The lambda static invoker function is special, because it forwards or
     // clones the body of the function call operator (but is actually static).
     EmitLambdaStaticInvokeBody(cast<CXXMethodDecl>(FD));
+
+  } else if (isa<CXXMethodDecl>(FD) &&
+             isLambdaCallOperator(cast<CXXMethodDecl>(FD)) &&
+             cast<CXXMethodDecl>(FD)->getParent()->getLambdaStaticInvoker() &&
+             hasInAllocaArg(cast<CXXMethodDecl>(FD)
+                                ->getParent()
+                                ->getLambdaStaticInvoker()) &&
+             !FnInfo.isDelegateCall()) {
+    // If emitting a lambda with static invoker on X86 Windows, change
+    // the call operator body.
+    EmitLambdaInAllocaCallOpBody(cast<CXXMethodDecl>(FD));
   } else if (FD->isDefaulted() && isa<CXXMethodDecl>(FD) &&
              (cast<CXXMethodDecl>(FD)->isCopyAssignmentOperator() ||
               cast<CXXMethodDecl>(FD)->isMoveAssignmentOperator())) {