Instcombine: destructor loads of structs that do not contains padding

For non padded structs, we can just proceed and deaggregate them.
We don't want ot do this when there is padding in the struct as to not
lose information about this padding (the subsequents passes would then
try hard to preserve the padding, which is undesirable).

Also update extractvalue.ll and cast.ll so that they use structs with padding.

Remove the FIXME in the extractvalue of laod case as the non padded case is
handled when processing the load, and we don't want to do it on the padded
case.

Patch by: Amaury SECHET <deadalnix@gmail.com>

Differential Revision: http://reviews.llvm.org/D14483

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 255600

1 files changed, 7 insertions, 2 deletions

diff --git a/llvm/lib/IR/DataLayout.cpp b/llvm/lib/IR/DataLayout.cpp
index 80a59e05bc5..5468f47bbfe 100644
--- a/llvm/lib/IR/DataLayout.cpp
+++ b/llvm/lib/IR/DataLayout.cpp
@@ -41,6 +41,7 @@ StructLayout::StructLayout(StructType *ST, const DataLayout &DL) {
   assert(!ST->isOpaque() && "Cannot get layout of opaque structs");
   StructAlignment = 0;
   StructSize = 0;
+  IsPadded = false;
   NumElements = ST->getNumElements();
 
   // Loop over each of the elements, placing them in memory.
@@ -49,8 +50,10 @@ StructLayout::StructLayout(StructType *ST, const DataLayout &DL) {
     unsigned TyAlign = ST->isPacked() ? 1 : DL.getABITypeAlignment(Ty);
 
     // Add padding if necessary to align the data element properly.
-    if ((StructSize & (TyAlign-1)) != 0)
+    if ((StructSize & (TyAlign-1)) != 0) {
+      IsPadded = true;
       StructSize = RoundUpToAlignment(StructSize, TyAlign);
+    }
 
     // Keep track of maximum alignment constraint.
     StructAlignment = std::max(TyAlign, StructAlignment);
@@ -64,8 +67,10 @@ StructLayout::StructLayout(StructType *ST, const DataLayout &DL) {
 
   // Add padding to the end of the struct so that it could be put in an array
   // and all array elements would be aligned correctly.
-  if ((StructSize & (StructAlignment-1)) != 0)
+  if ((StructSize & (StructAlignment-1)) != 0) {
+    IsPadded = true;
     StructSize = RoundUpToAlignment(StructSize, StructAlignment);
+  }
 }