[llvm] 47ee404 - [ValueTracking] Use Inst::comesBefore in isValidAssumeForCtx (NFC).

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2020-04-05T12:38:04+01:00
New Revision: 47ee40407562c296ace1cd0814a615890611e3b3

URL: https://github.com/llvm/llvm-project/commit/47ee40407562c296ace1cd0814a615890611e3b3
DIFF: https://github.com/llvm/llvm-project/commit/47ee40407562c296ace1cd0814a615890611e3b3.diff

LOG: [ValueTracking] Use Inst::comesBefore in isValidAssumeForCtx (NFC).

D51664 added Instruction::comesBefore which should provide better
performance than the manual check.

Reviewers: rnk, nikic, spatel

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D76228

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 6a4d596a3b76..d7ea47e50deb 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -617,6 +617,29 @@ bool llvm::isValidAssumeForContext(const Instruction *Inv,
   //     feeding the assume is trivially true, thus causing the removal of
   //     the assume).
 
+  if (Inv->getParent() == CxtI->getParent()) {
+    // If Inv and CtxI are in the same block, check if the assume (Inv) is first
+    // in the BB.
+    if (Inv->comesBefore(CxtI))
+      return true;
+
+    // Don't let an assume affect itself - this would cause the problems
+    // `isEphemeralValueOf` is trying to prevent, and it would also make
+    // the loop below go out of bounds.
+    if (Inv == CxtI)
+      return false;
+
+    // The context comes first, but they're both in the same block.
+    // Make sure there is nothing in between that might interrupt
+    // the control flow, not even CxtI itself.
+    for (BasicBlock::const_iterator I(CxtI), IE(Inv); I != IE; ++I)
+      if (!isGuaranteedToTransferExecutionToSuccessor(&*I))
+        return false;
+
+    return !isEphemeralValueOf(Inv, CxtI);
+  }
+
+  // Inv and CxtI are in 
diff erent blocks.
   if (DT) {
     if (DT->dominates(Inv, CxtI))
       return true;
@@ -625,37 +648,7 @@ bool llvm::isValidAssumeForContext(const Instruction *Inv,
     return true;
   }
 
-  // With or without a DT, the only remaining case we will check is if the
-  // instructions are in the same BB.  Give up if that is not the case.
-  if (Inv->getParent() != CxtI->getParent())
-    return false;
-
-  // If we have a dom tree, then we now know that the assume doesn't dominate
-  // the other instruction.  If we don't have a dom tree then we can check if
-  // the assume is first in the BB.
-  if (!DT) {
-    // Search forward from the assume until we reach the context (or the end
-    // of the block); the common case is that the assume will come first.
-    for (auto I = std::next(BasicBlock::const_iterator(Inv)),
-         IE = Inv->getParent()->end(); I != IE; ++I)
-      if (&*I == CxtI)
-        return true;
-  }
-
-  // Don't let an assume affect itself - this would cause the problems
-  // `isEphemeralValueOf` is trying to prevent, and it would also make
-  // the loop below go out of bounds.
-  if (Inv == CxtI)
-    return false;
-
-  // The context comes first, but they're both in the same block.
-  // Make sure there is nothing in between that might interrupt
-  // the control flow, not even CxtI itself.
-  for (BasicBlock::const_iterator I(CxtI), IE(Inv); I != IE; ++I)
-    if (!isGuaranteedToTransferExecutionToSuccessor(&*I))
-      return false;
-
-  return !isEphemeralValueOf(Inv, CxtI);
+  return false;
 }
 
 static bool isKnownNonZeroFromAssume(const Value *V, const Query &Q) {