Make globalopt refine global variable alignment.

llvm-svn: 100160

2 files changed, 13 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index ddff5ef8b36..c09e78e2693 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -1880,6 +1880,7 @@ bool GlobalOpt::OptimizeFunctions(Module &M) {
 
 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
   bool Changed = false;
+  TargetData *TD = getAnalysisIfAvailable<TargetData>();
   for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
        GVI != E; ) {
     GlobalVariable *GV = GVI++;
@@ -1889,11 +1890,16 @@ bool GlobalOpt::OptimizeGlobalVars(Module &M) {
     // Simplify the initializer.
     if (GV->hasInitializer())
       if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) {
-        TargetData *TD = getAnalysisIfAvailable<TargetData>();
         Constant *New = ConstantFoldConstantExpression(CE, TD);
         if (New && New != CE)
           GV->setInitializer(New);
       }
+    // Refine the alignment value.
+    if (TD && GV->hasDefinitiveInitializer()) {
+      unsigned Align = TD->getPreferredAlignment(GV);
+      if (Align > GV->getAlignment())
+        GV->setAlignment(Align);
+    }
     // Do more involved optimizations if the global is internal.
     if (!GV->isConstant() && GV->hasLocalLinkage() &&
         GV->hasInitializer())
diff --git a/llvm/test/Transforms/GlobalOpt/gv-align.ll b/llvm/test/Transforms/GlobalOpt/gv-align.ll
new file mode 100644
index 00000000000..f99e8a68450
--- /dev/null
+++ b/llvm/test/Transforms/GlobalOpt/gv-align.ll
@@ -0,0 +1,6 @@
+; RUN: opt -globalopt -S < %s | grep {, align 16}
+
+; Globalopt should refine the alignment for global variables.
+
+target datalayout = "e-p:64:64:64"
+@a = global [4 x i32] [i32 2, i32 3, i32 4, i32 5 ]