[InstCombine] Factor the logic for propagating !nonnull and !range

metadata out of InstCombine and into helpers.

NFC, this just exposes the logic used by InstCombine when propagating
metadata from one load instruction to another. The plan is to use this
in SROA to address PR32902.

If anyone has better ideas about how to factor this or name variables,
I'm all ears, but this seemed like a pretty good start and lets us make
progress on the PR.

This is based on a patch by Ariel Ben-Yehuda (D34285).

llvm-svn: 306267

2 files changed, 51 insertions, 31 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index ee30aa44674..ca370c73fca 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -489,21 +489,7 @@ static LoadInst *combineLoadToNewType(InstCombiner &IC, LoadInst &LI, Type *NewT
       break;
 
     case LLVMContext::MD_nonnull:
-      // This only directly applies if the new type is also a pointer.
-      if (NewTy->isPointerTy()) {
-        NewLoad->setMetadata(ID, N);
-        break;
-      }
-      // If it's integral now, translate it to !range metadata.
-      if (NewTy->isIntegerTy()) {
-        auto *ITy = cast<IntegerType>(NewTy);
-        auto *NullInt = ConstantExpr::getPtrToInt(
-            ConstantPointerNull::get(cast<PointerType>(Ptr->getType())), ITy);
-        auto *NonNullInt =
-            ConstantExpr::getAdd(NullInt, ConstantInt::get(ITy, 1));
-        NewLoad->setMetadata(LLVMContext::MD_range,
-                             MDB.createRange(NonNullInt, NullInt));
-      }
+      copyNonnullMetadata(LI, N, *NewLoad);
       break;
     case LLVMContext::MD_align:
     case LLVMContext::MD_dereferenceable:
@@ -513,17 +499,7 @@ static LoadInst *combineLoadToNewType(InstCombiner &IC, LoadInst &LI, Type *NewT
         NewLoad->setMetadata(ID, N);
       break;
     case LLVMContext::MD_range:
-      // FIXME: It would be nice to propagate this in some way, but the type
-      // conversions make it hard.
-
-      // If it's a pointer now and the range does not contain 0, make it !nonnull.
-      if (NewTy->isPointerTy()) {
-        unsigned BitWidth = IC.getDataLayout().getTypeSizeInBits(NewTy);
-        if (!getConstantRangeFromMetadata(*N).contains(APInt(BitWidth, 0))) {
-          MDNode *NN = MDNode::get(LI.getContext(), None);
-          NewLoad->setMetadata(LLVMContext::MD_nonnull, NN);
-        }
-      }
+      copyRangeMetadata(IC.getDataLayout(), LI, N, *NewLoad);
       break;
     }
   }
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 2af671636cb..5127eba3f9a 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -26,6 +26,7 @@
 #include "llvm/Analysis/MemoryBuiltins.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/CFG.h"
+#include "llvm/IR/ConstantRange.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DIBuilder.h"
 #include "llvm/IR/DataLayout.h"
@@ -1081,7 +1082,7 @@ static bool LdStHasDebugValue(DILocalVariable *DIVar, DIExpression *DIExpr,
 }
 
 /// See if there is a dbg.value intrinsic for DIVar for the PHI node.
-static bool PhiHasDebugValue(DILocalVariable *DIVar, 
+static bool PhiHasDebugValue(DILocalVariable *DIVar,
                              DIExpression *DIExpr,
                              PHINode *APN) {
   // Since we can't guarantee that the original dbg.declare instrinsic
@@ -1159,7 +1160,7 @@ void llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
   DbgValue->insertAfter(LI);
 }
 
-/// Inserts a llvm.dbg.value intrinsic after a phi 
+/// Inserts a llvm.dbg.value intrinsic after a phi
 /// that has an associated llvm.dbg.decl intrinsic.
 void llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
                                            PHINode *APN, DIBuilder &Builder) {
@@ -1742,12 +1743,12 @@ void llvm::combineMetadata(Instruction *K, const Instruction *J,
         // Preserve !invariant.group in K.
         break;
       case LLVMContext::MD_align:
-        K->setMetadata(Kind, 
+        K->setMetadata(Kind,
           MDNode::getMostGenericAlignmentOrDereferenceable(JMD, KMD));
         break;
       case LLVMContext::MD_dereferenceable:
       case LLVMContext::MD_dereferenceable_or_null:
-        K->setMetadata(Kind, 
+        K->setMetadata(Kind,
           MDNode::getMostGenericAlignmentOrDereferenceable(JMD, KMD));
         break;
     }
@@ -1847,6 +1848,49 @@ bool llvm::callsGCLeafFunction(ImmutableCallSite CS) {
   return false;
 }
 
+void llvm::copyNonnullMetadata(const LoadInst &OldLI, MDNode *N,
+                               LoadInst &NewLI) {
+  auto *NewTy = NewLI.getType();
+
+  // This only directly applies if the new type is also a pointer.
+  if (NewTy->isPointerTy()) {
+    NewLI.setMetadata(LLVMContext::MD_nonnull, N);
+    return;
+  }
+
+  // The only other translation we can do is to integral loads with !range
+  // metadata.
+  if (!NewTy->isIntegerTy())
+    return;
+
+  MDBuilder MDB(NewLI.getContext());
+  const Value *Ptr = OldLI.getPointerOperand();
+  auto *ITy = cast<IntegerType>(NewTy);
+  auto *NullInt = ConstantExpr::getPtrToInt(
+      ConstantPointerNull::get(cast<PointerType>(Ptr->getType())), ITy);
+  auto *NonNullInt = ConstantExpr::getAdd(NullInt, ConstantInt::get(ITy, 1));
+  NewLI.setMetadata(LLVMContext::MD_range,
+                    MDB.createRange(NonNullInt, NullInt));
+}
+
+void llvm::copyRangeMetadata(const DataLayout &DL, const LoadInst &OldLI,
+                             MDNode *N, LoadInst &NewLI) {
+  auto *NewTy = NewLI.getType();
+
+  // Give up unless it is converted to a pointer where there is a single very
+  // valuable mapping we can do reliably.
+  // FIXME: It would be nice to propagate this in more ways, but the type
+  // conversions make it hard.
+  if (!NewTy->isPointerTy())
+    return;
+
+  unsigned BitWidth = DL.getTypeSizeInBits(NewTy);
+  if (!getConstantRangeFromMetadata(*N).contains(APInt(BitWidth, 0))) {
+    MDNode *NN = MDNode::get(OldLI.getContext(), None);
+    NewLI.setMetadata(LLVMContext::MD_nonnull, NN);
+  }
+}
+
 namespace {
 /// A potential constituent of a bitreverse or bswap expression. See
 /// collectBitParts for a fuller explanation.
@@ -1968,7 +2012,7 @@ collectBitParts(Value *V, bool MatchBSwaps, bool MatchBitReversals,
       unsigned NumMaskedBits = AndMask.countPopulation();
       if (!MatchBitReversals && NumMaskedBits % 8 != 0)
         return Result;
-      
+
       auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps,
                                   MatchBitReversals, BPS);
       if (!Res)