From c46619aba2f23752fb2aec3236371251f49744b5 Mon Sep 17 00:00:00 2001
From: Sanjoy Das <sanjoy@playingwithpointers.com>
Date: Mon, 23 May 2016 22:16:45 +0000
Subject: [PATCH] [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
---
 .../Scalar/InductiveRangeCheckElimination.cpp | 19 ++++++++++---------
 test/Transforms/IRCE/only-lower-check.ll      |  2 +-
 test/Transforms/IRCE/only-upper-check.ll      |  2 +-
 3 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp b/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
index 5b4b6c14693..2b9f3f59c8e 100644
--- a/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
+++ b/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);
     }
   }
 
diff --git a/test/Transforms/IRCE/only-lower-check.ll b/test/Transforms/IRCE/only-lower-check.ll
index 69abc89c1a6..428c3aabdec 100644
--- a/test/Transforms/IRCE/only-lower-check.ll
+++ b/test/Transforms/IRCE/only-lower-check.ll
@@ -4,7 +4,7 @@
 ; CHECK-NEXT: InductiveRangeCheck:
 ; CHECK-NEXT:   Kind: RANGE_CHECK_LOWER
 ; CHECK-NEXT:   Offset: (-1 + %n)  Scale: -1  Length: (null)
-; CHECK-NEXT:   Branch:   br i1 %abc, label %in.bounds, label %out.of.bounds
+; CHECK-NEXT:   CheckUse:   br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1 Operand: 0
 ; CHECK-NEXT: irce: in function only_lower_check: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
 
 define void @only_lower_check(i32 *%arr, i32 *%a_len_ptr, i32 %n) {
diff --git a/test/Transforms/IRCE/only-upper-check.ll b/test/Transforms/IRCE/only-upper-check.ll
index dda3f3f6dd8..8e3e1ffe99b 100644
--- a/test/Transforms/IRCE/only-upper-check.ll
+++ b/test/Transforms/IRCE/only-upper-check.ll
@@ -4,7 +4,7 @@
 ; CHECK-NEXT:InductiveRangeCheck:
 ; CHECK-NEXT:  Kind: RANGE_CHECK_UPPER
 ; CHECK-NEXT:  Offset: %offset  Scale: 1  Length:   %len = load i32, i32* %a_len_ptr, !range !0
-; CHECK-NEXT:  Branch:   br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1
+; CHECK-NEXT:  CheckUse:   br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1 Operand: 0
 ; CHECK-NEXT: irce: in function incrementing: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
 
 define void @incrementing(i32 *%arr, i32 *%a_len_ptr, i32 %n, i32 %offset) {