make clang emit undefs for padding of structs and unions instead of zeros. this enables constant compaction optimizations.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@85504 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 5 insertions, 5 deletions

diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index dc0aa9e7c4..9145d92128 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -228,7 +228,7 @@ class VISIBILITY_HIDDEN ConstStructBuilder {
     if (NumBytes > 1)
       Ty = llvm::ArrayType::get(Ty, NumBytes);
 
-    llvm::Constant *C = llvm::Constant::getNullValue(Ty);
+    llvm::Constant *C = llvm::UndefValue::get(Ty);
     Elements.push_back(C);
     assert(getAlignment(C) == 1 && "Padding must have 1 byte alignment!");
 
@@ -266,7 +266,7 @@ class VISIBILITY_HIDDEN ConstStructBuilder {
         if (NumBytes > 1)
           Ty = llvm::ArrayType::get(Ty, NumBytes);
 
-        llvm::Constant *Padding = llvm::Constant::getNullValue(Ty);
+        llvm::Constant *Padding = llvm::UndefValue::get(Ty);
         PackedElements.push_back(Padding);
         ElementOffsetInBytes += getSizeInBytes(Padding);
       }
@@ -496,7 +496,7 @@ public:
         if (NumPadBytes > 1)
           Ty = llvm::ArrayType::get(Ty, NumPadBytes);
 
-        Elts.push_back(llvm::Constant::getNullValue(Ty));
+        Elts.push_back(llvm::UndefValue::get(Ty));
         Types.push_back(Ty);
       }
 
diff --git a/test/CodeGen/cast-to-union.c b/test/CodeGen/cast-to-union.c
index 6742992949..1f7e045770 100644
--- a/test/CodeGen/cast-to-union.c
+++ b/test/CodeGen/cast-to-union.c
@@ -1,5 +1,5 @@
 // RUN: clang-cc -emit-llvm  %s -o - | FileCheck %s
-// CHECK: w = global %0 { i32 2, [4 x i8] zeroinitializer }
+// CHECK: w = global %0 { i32 2, [4 x i8] undef }
 // CHECK: y = global %union.u { double 7.300000e+0{{[0]*}}1 }
 // CHECK: store i32 351, i32
 
diff --git a/test/CodeGen/union-init2.c b/test/CodeGen/union-init2.c
index 184d75f471..e782425cf2 100644
--- a/test/CodeGen/union-init2.c
+++ b/test/CodeGen/union-init2.c
@@ -1,4 +1,4 @@
-// RUN: clang-cc -emit-llvm %s -o - -triple i686-pc-linux-gnu | grep "bitcast (%0\* @r to %union.x\*), \[4 x i8\] zeroinitializer"
+// RUN: clang-cc -emit-llvm %s -o - -triple i686-pc-linux-gnu | grep "bitcast (%0\* @r to %union.x\*), \[4 x i8\] undef"
 
 // Make sure we generate something sane instead of a ptrtoint
 union x {long long b;union x* a;} r = {.a = &r};