vendor/llvm/llvm-trunk-r351319

1 files changed, 32 insertions, 20 deletions

diff --git a/lib/Transforms/Scalar/BDCE.cpp b/lib/Transforms/Scalar/BDCE.cpp
index 3a8ef073cb48..d3c9b9a270aa 100644
--- a/lib/Transforms/Scalar/BDCE.cpp
+++ b/lib/Transforms/Scalar/BDCE.cpp
@@ -38,7 +38,8 @@ STATISTIC(NumSimplified, "Number of instructions trivialized (dead bits)");
 /// instruction may need to be cleared of assumptions that can no longer be
 /// guaranteed correct.
 static void clearAssumptionsOfUsers(Instruction *I, DemandedBits &DB) {
-  assert(I->getType()->isIntegerTy() && "Trivializing a non-integer value?");
+  assert(I->getType()->isIntOrIntVectorTy() &&
+         "Trivializing a non-integer value?");
 
   // Initialize the worklist with eligible direct users.
   SmallVector<Instruction *, 16> WorkList;
@@ -46,13 +47,13 @@ static void clearAssumptionsOfUsers(Instruction *I, DemandedBits &DB) {
     // If all bits of a user are demanded, then we know that nothing below that
     // in the def-use chain needs to be changed.
     auto *J = dyn_cast<Instruction>(JU);
-    if (J && J->getType()->isSized() &&
+    if (J && J->getType()->isIntOrIntVectorTy() &&
         !DB.getDemandedBits(J).isAllOnesValue())
       WorkList.push_back(J);
 
-    // Note that we need to check for unsized types above before asking for
+    // Note that we need to check for non-int types above before asking for
     // demanded bits. Normally, the only way to reach an instruction with an
-    // unsized type is via an instruction that has side effects (or otherwise
+    // non-int type is via an instruction that has side effects (or otherwise
     // will demand its input bits). However, if we have a readnone function
     // that returns an unsized type (e.g., void), we must avoid asking for the
     // demanded bits of the function call's return value. A void-returning
@@ -78,7 +79,7 @@ static void clearAssumptionsOfUsers(Instruction *I, DemandedBits &DB) {
       // If all bits of a user are demanded, then we know that nothing below
       // that in the def-use chain needs to be changed.
       auto *K = dyn_cast<Instruction>(KU);
-      if (K && !Visited.count(K) && K->getType()->isSized() &&
+      if (K && !Visited.count(K) && K->getType()->isIntOrIntVectorTy() &&
           !DB.getDemandedBits(K).isAllOnesValue())
         WorkList.push_back(K);
     }
@@ -95,30 +96,41 @@ static bool bitTrackingDCE(Function &F, DemandedBits &DB) {
     if (I.mayHaveSideEffects() && I.use_empty())
       continue;
 
-    if (I.getType()->isIntegerTy() &&
-        !DB.getDemandedBits(&I).getBoolValue()) {
-      // For live instructions that have all dead bits, first make them dead by
-      // replacing all uses with something else. Then, if they don't need to
-      // remain live (because they have side effects, etc.) we can remove them.
-      LLVM_DEBUG(dbgs() << "BDCE: Trivializing: " << I << " (all bits dead)\n");
+    // Remove instructions that are dead, either because they were not reached
+    // during analysis or have no demanded bits.
+    if (DB.isInstructionDead(&I) ||
+        (I.getType()->isIntOrIntVectorTy() &&
+         DB.getDemandedBits(&I).isNullValue() &&
+         wouldInstructionBeTriviallyDead(&I))) {
+      salvageDebugInfo(I);
+      Worklist.push_back(&I);
+      I.dropAllReferences();
+      Changed = true;
+      continue;
+    }
+
+    for (Use &U : I.operands()) {
+      // DemandedBits only detects dead integer uses.
+      if (!U->getType()->isIntOrIntVectorTy())
+        continue;
+
+      if (!isa<Instruction>(U) && !isa<Argument>(U))
+        continue;
+
+      if (!DB.isUseDead(&U))
+        continue;
+
+      LLVM_DEBUG(dbgs() << "BDCE: Trivializing: " << U << " (all bits dead)\n");
 
       clearAssumptionsOfUsers(&I, DB);
 
       // FIXME: In theory we could substitute undef here instead of zero.
       // This should be reconsidered once we settle on the semantics of
       // undef, poison, etc.
-      Value *Zero = ConstantInt::get(I.getType(), 0);
+      U.set(ConstantInt::get(U->getType(), 0));
       ++NumSimplified;
-      I.replaceNonMetadataUsesWith(Zero);
       Changed = true;
     }
-    if (!DB.isInstructionDead(&I))
-      continue;
-
-    salvageDebugInfo(I);
-    Worklist.push_back(&I);
-    I.dropAllReferences();
-    Changed = true;
   }
 
   for (Instruction *&I : Worklist) {