[IRCE] Optimize "uses" not branches; NFCI

This changes IRCE to optimize uses, and not branches.  This change is
NFCI since the uses we do inspect are in practice only ever going to be
the condition use in conditional branches; but this flexibility will
later allow us to analyze more complex expressions than just a direct
branch on a range check.

llvm-svn: 270500

1 files changed, 10 insertions, 9 deletions

diff --git a/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp b/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
index 5b4b6c14693..2b9f3f59c8e 100644
--- a/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
@@ -118,7 +118,7 @@ class InductiveRangeCheck {
   const SCEV *Offset;
   const SCEV *Scale;
   Value *Length;
-  BranchInst *Branch;
+  Use *CheckUse;
   RangeCheckKind Kind;
 
   static RangeCheckKind parseRangeCheckICmp(Loop *L, ICmpInst *ICI,
@@ -129,8 +129,9 @@ class InductiveRangeCheck {
   parseRangeCheck(Loop *L, ScalarEvolution &SE, Value *Condition,
                   const SCEV *&Index, Value *&UpperLimit);
 
-  InductiveRangeCheck() :
-    Offset(nullptr), Scale(nullptr), Length(nullptr), Branch(nullptr) { }
+  InductiveRangeCheck()
+      : Offset(nullptr), Scale(nullptr), Length(nullptr),
+        CheckUse(nullptr) {}
 
 public:
   const SCEV *getOffset() const { return Offset; }
@@ -149,9 +150,9 @@ public:
       Length->print(OS);
     else
       OS << "(null)";
-    OS << "\n  Branch: ";
-    getBranch()->print(OS);
-    OS << "\n";
+    OS << "\n  CheckUse: ";
+    getCheckUse()->getUser()->print(OS);
+    OS << " Operand: " << getCheckUse()->getOperandNo() << "\n";
   }
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
@@ -160,7 +161,7 @@ public:
   }
 #endif
 
-  BranchInst *getBranch() const { return Branch; }
+  Use *getCheckUse() const { return CheckUse; }
 
   /// Represents an signed integer range [Range.getBegin(), Range.getEnd()).  If
   /// R.getEnd() sle R.getBegin(), then R denotes the empty range.
@@ -407,7 +408,7 @@ InductiveRangeCheck::create(BranchInst *BI, Loop *L, ScalarEvolution &SE,
   IRC.Length = Length;
   IRC.Offset = IndexAddRec->getStart();
   IRC.Scale = IndexAddRec->getStepRecurrence(SE);
-  IRC.Branch = BI;
+  IRC.CheckUse = &BI->getOperandUse(0);
   IRC.Kind = RCKind;
   return IRC;
 }
@@ -1474,7 +1475,7 @@ bool InductiveRangeCheckElimination::runOnLoop(Loop *L, LPPassManager &LPM) {
       ConstantInt *FoldedRangeCheck = IRC.getPassingDirection()
                                           ? ConstantInt::getTrue(Context)
                                           : ConstantInt::getFalse(Context);
-      IRC.getBranch()->setCondition(FoldedRangeCheck);
+      IRC.getCheckUse()->set(FoldedRangeCheck);
     }
   }