[DebugInfo] Don't turn dbg.declare into DBG_VALUE for static allocas

Summary:
We already have information about static alloca stack locations in our
side table. Emitting instructions for them is inefficient, and it only
happens when the address of the alloca has been materialized within the
current block, which isn't often.

Reviewers: aprantl, probinson, dblaikie

Subscribers: jfb, dschuff, sbc100, jgravelle-google, hiraditya, llvm-commits, aheejin

Differential Revision: https://reviews.llvm.org/D36117

llvm-svn: 309729

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 4e19ec32a3a..e90db4803ee 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -5102,6 +5102,13 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
       return nullptr;
     }
 
+    // Static allocas are handled more efficiently in the variable frame index
+    // side table.
+    const auto *AI =
+        dyn_cast<AllocaInst>(Address->stripInBoundsConstantOffsets());
+    if (AI && AI->isStaticAlloca() && FuncInfo.StaticAllocaMap.count(AI))
+      return nullptr;
+
     // Byval arguments with frame indices were already handled after argument
     // lowering and before isel.
     const auto *Arg =