[IR] Add llvm.dbg.addr, a control-dependent version of llvm.dbg.declare

Summary:
This implements the design discussed on llvm-dev for better tracking of
variables that live in memory through optimizations:
  http://lists.llvm.org/pipermail/llvm-dev/2017-September/117222.html

This is tracked as PR34136

llvm.dbg.addr is intended to be produced and used in almost precisely
the same way as llvm.dbg.declare is today, with the exception that it is
control-dependent. That means that dbg.addr should always have a
position in the instruction stream, and it will allow passes that
optimize memory operations on local variables to insert llvm.dbg.value
calls to reflect deleted stores. See SourceLevelDebugging.rst for more
details.

The main drawback to generating DBG_VALUE machine instrs is that they
usually cause LLVM to emit a location list for DW_AT_location. The next
step will be to teach DwarfDebug.cpp how to recognize more DBG_VALUE
ranges as not needing a location list, and possibly start setting
DW_AT_start_offset for variables whose lifetimes begin mid-scope.

Reviewers: aprantl, dblaikie, probinson

Subscribers: eraman, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D37768

llvm-svn: 313825

1 files changed, 22 insertions, 22 deletions

diff --git a/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp b/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
index ac28f590b01..e2ba5c4cfbb 100644
--- a/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
+++ b/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
@@ -103,7 +103,7 @@ struct AllocaInfo {
   bool OnlyUsedInOneBlock;
 
   Value *AllocaPointerVal;
-  DbgDeclareInst *DbgDeclare;
+  TinyPtrVector<DbgInfoIntrinsic*> DbgDeclares;
 
   void clear() {
     DefiningBlocks.clear();
@@ -112,7 +112,7 @@ struct AllocaInfo {
     OnlyBlock = nullptr;
     OnlyUsedInOneBlock = true;
     AllocaPointerVal = nullptr;
-    DbgDeclare = nullptr;
+    DbgDeclares.clear();
   }
 
   /// Scan the uses of the specified alloca, filling in the AllocaInfo used
@@ -147,7 +147,7 @@ struct AllocaInfo {
       }
     }
 
-    DbgDeclare = FindAllocaDbgDeclare(AI);
+    DbgDeclares = FindDbgAddrUses(AI);
   }
 };
 
@@ -245,7 +245,7 @@ struct PromoteMem2Reg {
   /// For each alloca, we keep track of the dbg.declare intrinsic that
   /// describes it, if any, so that we can convert it to a dbg.value
   /// intrinsic if the alloca gets promoted.
-  SmallVector<DbgDeclareInst *, 8> AllocaDbgDeclares;
+  SmallVector<TinyPtrVector<DbgInfoIntrinsic *>, 8> AllocaDbgDeclares;
 
   /// The set of basic blocks the renamer has already visited.
   ///
@@ -409,11 +409,11 @@ static bool rewriteSingleStoreAlloca(AllocaInst *AI, AllocaInfo &Info,
 
   // Record debuginfo for the store and remove the declaration's
   // debuginfo.
-  if (DbgDeclareInst *DDI = Info.DbgDeclare) {
+  for (DbgInfoIntrinsic *DII : Info.DbgDeclares) {
     DIBuilder DIB(*AI->getModule(), /*AllowUnresolved*/ false);
-    ConvertDebugDeclareToDebugValue(DDI, Info.OnlyStore, DIB);
-    DDI->eraseFromParent();
-    LBI.deleteValue(DDI);
+    ConvertDebugDeclareToDebugValue(DII, Info.OnlyStore, DIB);
+    DII->eraseFromParent();
+    LBI.deleteValue(DII);
   }
   // Remove the (now dead) store and alloca.
   Info.OnlyStore->eraseFromParent();
@@ -505,9 +505,9 @@ static bool promoteSingleBlockAlloca(AllocaInst *AI, const AllocaInfo &Info,
   while (!AI->use_empty()) {
     StoreInst *SI = cast<StoreInst>(AI->user_back());
     // Record debuginfo for the store before removing it.
-    if (DbgDeclareInst *DDI = Info.DbgDeclare) {
+    for (DbgInfoIntrinsic *DII : Info.DbgDeclares) {
       DIBuilder DIB(*AI->getModule(), /*AllowUnresolved*/ false);
-      ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
+      ConvertDebugDeclareToDebugValue(DII, SI, DIB);
     }
     SI->eraseFromParent();
     LBI.deleteValue(SI);
@@ -517,9 +517,9 @@ static bool promoteSingleBlockAlloca(AllocaInst *AI, const AllocaInfo &Info,
   LBI.deleteValue(AI);
 
   // The alloca's debuginfo can be removed as well.
-  if (DbgDeclareInst *DDI = Info.DbgDeclare) {
-    DDI->eraseFromParent();
-    LBI.deleteValue(DDI);
+  for (DbgInfoIntrinsic *DII : Info.DbgDeclares) {
+    DII->eraseFromParent();
+    LBI.deleteValue(DII);
   }
 
   ++NumLocalPromoted;
@@ -587,8 +587,8 @@ void PromoteMem2Reg::run() {
     }
 
     // Remember the dbg.declare intrinsic describing this alloca, if any.
-    if (Info.DbgDeclare)
-      AllocaDbgDeclares[AllocaNum] = Info.DbgDeclare;
+    if (!Info.DbgDeclares.empty())
+      AllocaDbgDeclares[AllocaNum] = Info.DbgDeclares;
 
     // Keep the reverse mapping of the 'Allocas' array for the rename pass.
     AllocaLookup[Allocas[AllocaNum]] = AllocaNum;
@@ -666,9 +666,9 @@ void PromoteMem2Reg::run() {
   }
 
   // Remove alloca's dbg.declare instrinsics from the function.
-  for (DbgDeclareInst *DDI : AllocaDbgDeclares)
-    if (DDI)
-      DDI->eraseFromParent();
+  for (auto &Declares : AllocaDbgDeclares)
+    for (auto *DII : Declares)
+      DII->eraseFromParent();
 
   // Loop over all of the PHI nodes and see if there are any that we can get
   // rid of because they merge all of the same incoming values.  This can
@@ -895,8 +895,8 @@ NextIteration:
 
         // The currently active variable for this block is now the PHI.
         IncomingVals[AllocaNo] = APN;
-        if (DbgDeclareInst *DDI = AllocaDbgDeclares[AllocaNo])
-          ConvertDebugDeclareToDebugValue(DDI, APN, DIB);
+        for (DbgInfoIntrinsic *DII : AllocaDbgDeclares[AllocaNo])
+          ConvertDebugDeclareToDebugValue(DII, APN, DIB);
 
         // Get the next phi node.
         ++PNI;
@@ -952,8 +952,8 @@ NextIteration:
       // what value were we writing?
       IncomingVals[ai->second] = SI->getOperand(0);
       // Record debuginfo for the store before removing it.
-      if (DbgDeclareInst *DDI = AllocaDbgDeclares[ai->second])
-        ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
+      for (DbgInfoIntrinsic *DII : AllocaDbgDeclares[ai->second])
+        ConvertDebugDeclareToDebugValue(DII, SI, DIB);
       BB->getInstList().erase(SI);
     }
   }