Add field PaddingType to ABIArgInfo which specifies the type of padding that

is inserted before the real argument. Padding is needed to ensure the backend
reads from or writes to the correct argument slots when the original alignment
of a byval structure is unavailable due to flattening.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@147699 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 0 deletions

diff --git a/lib/CodeGen/CGCall.cpp b/lib/CodeGen/CGCall.cpp
index 3457b5bc14..962339ab77 100644
--- a/lib/CodeGen/CGCall.cpp
+++ b/lib/CodeGen/CGCall.cpp
@@ -686,6 +686,9 @@ CodeGenTypes::GetFunctionType(const CGFunctionInfo &FI, bool isVariadic) {
 
     case ABIArgInfo::Extend:
     case ABIArgInfo::Direct: {
+      // Insert a padding type to ensure proper alignment.
+      if (llvm::Type *PaddingType = argAI.getPaddingType())
+        argTypes.push_back(PaddingType);
       // If the coerce-to type is a first class aggregate, flatten it.  Either
       // way is semantically identical, but fast-isel and the optimizer
       // generally likes scalar values better than FCAs.
@@ -840,6 +843,9 @@ void CodeGenModule::ConstructAttributeList(const CGFunctionInfo &FI,
       }
       // FIXME: handle sseregparm someday...
 
+      // Increment Index if there is padding.
+      Index += (AI.getPaddingType() != 0);
+
       if (llvm::StructType *STy =
             dyn_cast<llvm::StructType>(AI.getCoerceToType()))
         Index += STy->getNumElements()-1;  // 1 will be added below.
@@ -1024,6 +1030,10 @@ void CodeGenFunction::EmitFunctionProlog(const CGFunctionInfo &FI,
                           llvm::PointerType::getUnqual(ArgI.getCoerceToType()));
       }
 
+      // Skip the dummy padding argument.
+      if (ArgI.getPaddingType())
+        ++AI;
+
       // If the coerce-to type is a first class aggregate, we flatten it and
       // pass the elements. Either way is semantically identical, but fast-isel
       // and the optimizer generally likes scalar values better than FCAs.
@@ -1658,6 +1668,12 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
 
     case ABIArgInfo::Extend:
     case ABIArgInfo::Direct: {
+      // Insert a padding argument to ensure proper alignment.
+      if (llvm::Type *PaddingType = ArgInfo.getPaddingType()) {
+        Args.push_back(llvm::UndefValue::get(PaddingType));
+        ++IRArgNo;
+      }
+
       if (!isa<llvm::StructType>(ArgInfo.getCoerceToType()) &&
           ArgInfo.getCoerceToType() == ConvertType(info_it->type) &&
           ArgInfo.getDirectOffset() == 0) {