From 30e33b4b81115e9ace72e0435a6109946ddda1cd Mon Sep 17 00:00:00 2001
From: Max Kazantsev <mkazantsev@azul.com>
Date: Wed, 13 Jul 2022 18:53:29 +0700
Subject: [PATCH] [SCEV][NFC] Make getStrengthenedNoWrapFlagsFromBinOp return
 optional

---
 llvm/include/llvm/Analysis/ScalarEvolution.h |  6 ++++--
 llvm/lib/Analysis/ScalarEvolution.cpp        | 15 +++++++++------
 llvm/lib/Transforms/Utils/SimplifyIndVar.cpp | 14 ++++++--------
 3 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/llvm/include/llvm/Analysis/ScalarEvolution.h b/llvm/include/llvm/Analysis/ScalarEvolution.h
index de1cc29..5b49ab1 100644
--- a/llvm/include/llvm/Analysis/ScalarEvolution.h
+++ b/llvm/include/llvm/Analysis/ScalarEvolution.h
@@ -535,8 +535,10 @@ public:
 
   /// Parse NSW/NUW flags from add/sub/mul IR binary operation \p Op into
   /// SCEV no-wrap flags, and deduce flag[s] that aren't known yet.
-  /// Does not mutate the original instruction.
-  std::pair<SCEV::NoWrapFlags, bool /*Deduced*/>
+  /// Does not mutate the original instruction. Returns None if it could not
+  /// deduce more precise flags than the instruction already has, otherwise
+  /// returns proven flags.
+  Optional<SCEV::NoWrapFlags>
   getStrengthenedNoWrapFlagsFromBinOp(const OverflowingBinaryOperator *OBO);
 
   /// Notify this ScalarEvolution that \p User directly uses SCEVs in \p Ops.
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index e8aa99c..f73fd49 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -2319,9 +2319,13 @@ bool ScalarEvolution::willNotOverflow(Instruction::BinaryOps BinOp, bool Signed,
   return A == B;
 }
 
-std::pair<SCEV::NoWrapFlags, bool /*Deduced*/>
+Optional<SCEV::NoWrapFlags>
 ScalarEvolution::getStrengthenedNoWrapFlagsFromBinOp(
     const OverflowingBinaryOperator *OBO) {
+  // It cannot be done any better.
+  if (OBO->hasNoUnsignedWrap() && OBO->hasNoSignedWrap())
+    return None;
+
   SCEV::NoWrapFlags Flags = SCEV::NoWrapFlags::FlagAnyWrap;
 
   if (OBO->hasNoUnsignedWrap())
@@ -2331,13 +2335,10 @@ ScalarEvolution::getStrengthenedNoWrapFlagsFromBinOp(
 
   bool Deduced = false;
 
-  if (OBO->hasNoUnsignedWrap() && OBO->hasNoSignedWrap())
-    return {Flags, Deduced};
-
   if (OBO->getOpcode() != Instruction::Add &&
       OBO->getOpcode() != Instruction::Sub &&
       OBO->getOpcode() != Instruction::Mul)
-    return {Flags, Deduced};
+    return None;
 
   const SCEV *LHS = getSCEV(OBO->getOperand(0));
   const SCEV *RHS = getSCEV(OBO->getOperand(1));
@@ -2356,7 +2357,9 @@ ScalarEvolution::getStrengthenedNoWrapFlagsFromBinOp(
     Deduced = true;
   }
 
-  return {Flags, Deduced};
+  if (Deduced)
+    return Flags;
+  return None;
 }
 
 // We're trying to construct a SCEV of type `Type' with `Ops' as operands and
diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index 64546ae..153fa36 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -749,17 +749,15 @@ bool SimplifyIndvar::eliminateIdentitySCEV(Instruction *UseInst,
 /// unsigned-overflow.  Returns true if anything changed, false otherwise.
 bool SimplifyIndvar::strengthenOverflowingOperation(BinaryOperator *BO,
                                                     Value *IVOperand) {
-  SCEV::NoWrapFlags Flags;
-  bool Deduced;
-  std::tie(Flags, Deduced) = SE->getStrengthenedNoWrapFlagsFromBinOp(
+  auto Flags = SE->getStrengthenedNoWrapFlagsFromBinOp(
       cast<OverflowingBinaryOperator>(BO));
 
-  if (!Deduced)
-    return Deduced;
+  if (!Flags)
+    return false;
 
-  BO->setHasNoUnsignedWrap(ScalarEvolution::maskFlags(Flags, SCEV::FlagNUW) ==
+  BO->setHasNoUnsignedWrap(ScalarEvolution::maskFlags(*Flags, SCEV::FlagNUW) ==
                            SCEV::FlagNUW);
-  BO->setHasNoSignedWrap(ScalarEvolution::maskFlags(Flags, SCEV::FlagNSW) ==
+  BO->setHasNoSignedWrap(ScalarEvolution::maskFlags(*Flags, SCEV::FlagNSW) ==
                          SCEV::FlagNSW);
 
   // The getStrengthenedNoWrapFlagsFromBinOp() check inferred additional nowrap
@@ -767,7 +765,7 @@ bool SimplifyIndvar::strengthenOverflowingOperation(BinaryOperator *BO,
   // forgetValue() here to make sure those flags also propagate to any other
   // SCEV expressions based on the addrec. However, this can have pathological
   // compile-time impact, see https://bugs.llvm.org/show_bug.cgi?id=50384.
-  return Deduced;
+  return true;
 }
 
 /// Annotate the Shr in (X << IVOperand) >> C as exact using the
-- 
2.7.4