Factor out a helper function for readability and reuse in a future patch [NFC]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@362980 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Analysis/ValueTracking.h b/include/llvm/Analysis/ValueTracking.h
index 8e03b77..d14da32 100644 (file)
--- a/include/llvm/Analysis/ValueTracking.h
+++ b/include/llvm/Analysis/ValueTracking.h
@@ -16,6 +16,7 @@
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/Optional.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Instruction.h"
@@ -521,6 +522,12 @@ class Value;
   /// value (all bits poison).
   const Value *getGuaranteedNonFullPoisonOp(const Instruction *I);
 
+  /// Return true if the given instruction must trigger undefined behavior.
+  /// when I is executed with any operands which appear in KnownPoison holding
+  /// a full-poison value at the point of execution.
+  bool mustTriggerUB(const Instruction *I,
+                     const SmallSet<const Value *, 16>& KnownPoison);
+
   /// Return true if this function can prove that if PoisonI is executed
   /// and yields a full-poison value (all bits poison), then that will
   /// trigger undefined behavior.

diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 6400637..e132654 100644 (file)
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -4392,6 +4392,13 @@ const Value *llvm::getGuaranteedNonFullPoisonOp(const Instruction *I) {
   }
 }
 
+bool llvm::mustTriggerUB(const Instruction *I,
+                         const SmallSet<const Value *, 16>& KnownPoison) {
+  auto *NotPoison = getGuaranteedNonFullPoisonOp(I);
+  return (NotPoison && KnownPoison.count(NotPoison));
+}
+
+
 bool llvm::programUndefinedIfFullPoison(const Instruction *PoisonI) {
   // We currently only look for uses of poison values within the same basic
   // block, as that makes it easier to guarantee that the uses will be
@@ -4415,8 +4422,7 @@ bool llvm::programUndefinedIfFullPoison(const Instruction *PoisonI) {
   while (Iter++ < MaxDepth) {
     for (auto &I : make_range(Begin, End)) {
       if (&I != PoisonI) {
-        const Value *NotPoison = getGuaranteedNonFullPoisonOp(&I);
-        if (NotPoison != nullptr && YieldsPoison.count(NotPoison))
+        if (mustTriggerUB(&I, YieldsPoison))
           return true;
         if (!isGuaranteedToTransferExecutionToSuccessor(&I))
           return false;