From ac1a97b32fbc2d8f1a95f76714c5b729b6f251ce Mon Sep 17 00:00:00 2001
From: Reid Kleckner <rnk@google.com>
Date: Fri, 5 May 2017 18:30:34 +0000
Subject: [PATCH] Simplify dbg.value handling in SDISel with early returns

No functional change other than improving dbgs logging accuracy on
constant dbg values. Previously we would add things like "i32 42" as
debug values, and then log that we were dropping the debug info, which
is silly.

Delete some dead code that was checking for static allocas. This
remained after r207165, but served no purpose. Currently, static alloca
dbg.values are always sent through the DanglingDebugInfoMap, and are
usually made valid the first time the alloca is used.

llvm-svn: 302267
---
 .../CodeGen/SelectionDAG/SelectionDAGBuilder.cpp   | 58 +++++++++-------------
 1 file changed, 23 insertions(+), 35 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index ba9e117..979c2fc 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4992,45 +4992,33 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
       SDV = DAG.getConstantDbgValue(Variable, Expression, V, Offset, dl,
                                     SDNodeOrder);
       DAG.AddDbgValue(SDV, nullptr, false);
-    } else {
-      // Do not use getValue() in here; we don't want to generate code at
-      // this point if it hasn't been done yet.
-      SDValue N = NodeMap[V];
-      if (!N.getNode() && isa<Argument>(V))
-        // Check unused arguments map.
-        N = UnusedArgNodeMap[V];
-      if (N.getNode()) {
-        if (!EmitFuncArgumentDbgValue(V, Variable, Expression, dl, Offset,
-                                      false, N)) {
-          SDV = getDbgValue(N, Variable, Expression, Offset, dl, SDNodeOrder);
-          DAG.AddDbgValue(SDV, N.getNode(), false);
-        }
-      } else if (!V->use_empty() ) {
-        // Do not call getValue(V) yet, as we don't want to generate code.
-        // Remember it for later.
-        DanglingDebugInfo DDI(&DI, dl, SDNodeOrder);
-        DanglingDebugInfoMap[V] = DDI;
-      } else {
-        // We may expand this to cover more cases.  One case where we have no
-        // data available is an unreferenced parameter.
-        DEBUG(dbgs() << "Dropping debug info for " << DI << "\n");
-      }
+      return nullptr;
+    }
+
+    // Do not use getValue() in here; we don't want to generate code at
+    // this point if it hasn't been done yet.
+    SDValue N = NodeMap[V];
+    if (!N.getNode() && isa<Argument>(V)) // Check unused arguments map.
+      N = UnusedArgNodeMap[V];
+    if (N.getNode()) {
+      if (EmitFuncArgumentDbgValue(V, Variable, Expression, dl, Offset, false,
+                                   N))
+        return nullptr;
+      SDV = getDbgValue(N, Variable, Expression, Offset, dl, SDNodeOrder);
+      DAG.AddDbgValue(SDV, N.getNode(), false);
+      return nullptr;
     }
 
-    // Build a debug info table entry.
-    if (const BitCastInst *BCI = dyn_cast<BitCastInst>(V))
-      V = BCI->getOperand(0);
-    const AllocaInst *AI = dyn_cast<AllocaInst>(V);
-    // Don't handle byval struct arguments or VLAs, for example.
-    if (!AI) {
-      DEBUG(dbgs() << "Dropping debug location info for:\n  " << DI << "\n");
-      DEBUG(dbgs() << "  Last seen at:\n    " << *V << "\n");
+    if (!V->use_empty() ) {
+      // Do not call getValue(V) yet, as we don't want to generate code.
+      // Remember it for later.
+      DanglingDebugInfo DDI(&DI, dl, SDNodeOrder);
+      DanglingDebugInfoMap[V] = DDI;
       return nullptr;
     }
-    DenseMap<const AllocaInst*, int>::iterator SI =
-      FuncInfo.StaticAllocaMap.find(AI);
-    if (SI == FuncInfo.StaticAllocaMap.end())
-      return nullptr; // VLAs.
+
+    DEBUG(dbgs() << "Dropping debug location info for:\n  " << DI << "\n");
+    DEBUG(dbgs() << "  Last seen at:\n    " << *V << "\n");
     return nullptr;
   }
 
-- 
2.7.4