[MS] Fix prologue this adjustment when 'this' is passed indirectly

Move the logic for doing this from the ABI argument lowering into
EmitParmDecl, which runs for all parameters. Our codegen is slightly
suboptimal in this case, as we may leave behind a dead store after
optimization, but it's 32-bit inalloca, and this fixes the bug in a
robust way.

Fixes PR30293

llvm-svn: 280836

1 files changed, 19 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 037b1351c0f..5b4017cad37 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -13,6 +13,7 @@
 
 #include "CodeGenFunction.h"
 #include "CGBlocks.h"
+#include "CGCXXABI.h"
 #include "CGCleanup.h"
 #include "CGDebugInfo.h"
 #include "CGOpenCLRuntime.h"
@@ -1769,6 +1770,24 @@ void CodeGenFunction::EmitParmDecl(const VarDecl &D, ParamValue Arg,
       setBlockContextParameter(IPD, ArgNo, Arg.getDirectValue());
       return;
     }
+
+    // Apply any prologue 'this' adjustments required by the ABI. Be careful to
+    // handle the case where 'this' is passed indirectly as part of an inalloca
+    // struct.
+    if (const CXXMethodDecl *MD =
+            dyn_cast_or_null<CXXMethodDecl>(CurCodeDecl)) {
+      if (MD->isVirtual() && IPD == CXXABIThisDecl) {
+        llvm::Value *This = Arg.isIndirect()
+                                ? Builder.CreateLoad(Arg.getIndirectAddress())
+                                : Arg.getDirectValue();
+        This = CGM.getCXXABI().adjustThisParameterInVirtualFunctionPrologue(
+            *this, CurGD, This);
+        if (Arg.isIndirect())
+          Builder.CreateStore(This, Arg.getIndirectAddress());
+        else
+          Arg = ParamValue::forDirect(This);
+      }
+    }
   }
 
   Address DeclPtr = Address::invalid();