SROA: Avoid creating a fragment expression that covers the entire variable.

Fixes PR35416.

https://bugs.llvm.org/show_bug.cgi?id=35416

llvm-svn: 319126

1 files changed, 9 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Scalar/SROA.cpp b/llvm/lib/Transforms/Scalar/SROA.cpp
index 85479609f3d..93321076a85 100644
--- a/llvm/lib/Transforms/Scalar/SROA.cpp
+++ b/llvm/lib/Transforms/Scalar/SROA.cpp
@@ -4101,6 +4101,7 @@ bool SROA::splitAlloca(AllocaInst &AI, AllocaSlices &AS) {
   if (!DbgDeclares.empty()) {
     auto *Var = DbgDeclares.front()->getVariable();
     auto *Expr = DbgDeclares.front()->getExpression();
+    auto VarSize = Var->getSizeInBits();
     DIBuilder DIB(*AI.getModule(), /*AllowUnresolved*/ false);
     uint64_t AllocaSize = DL.getTypeSizeInBits(AI.getAllocatedType());
     for (auto Fragment : Fragments) {
@@ -4128,10 +4129,14 @@ bool SROA::splitAlloca(AllocaInst &AI, AllocaSlices &AS) {
                  "new fragment is outside of original fragment");
           Start -= OrigFragment->OffsetInBits;
         }
-        if (auto E = DIExpression::createFragmentExpression(Expr, Start, Size))
-          FragmentExpr = *E;
-        else
-          continue;
+        // Avoid creating a fragment expression that covers the entire variable.
+        if (!VarSize || *VarSize != Size) {
+          if (auto E =
+                  DIExpression::createFragmentExpression(Expr, Start, Size))
+            FragmentExpr = *E;
+          else
+            continue;
+        }
       }
 
       // Remove any existing intrinsics describing the same alloca.