From 9d1434bbf22da8382c61883d033774b7ea8fa8dc Mon Sep 17 00:00:00 2001
From: Nikita Popov <nikita.ppv@gmail.com>
Date: Thu, 30 Jan 2020 22:54:35 +0100
Subject: [PATCH] [InstCombine] Create new insts in
 foldICmpEqIntrinsicWithConstant; NFCI

In line with current conventions, create new instructions rather
than modify two operands in place and performing manual worklist
management.

This should be NFC apart from possible worklist order changes.
---
 .../InstCombine/InstCombineCompares.cpp       | 42 +++++++------------
 1 file changed, 15 insertions(+), 27 deletions(-)

diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index beb786fc8d8..de37b723ac1 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3025,20 +3025,16 @@ Instruction *InstCombiner::foldICmpEqIntrinsicWithConstant(ICmpInst &Cmp,
   unsigned BitWidth = C.getBitWidth();
   switch (II->getIntrinsicID()) {
   case Intrinsic::bswap:
-    Worklist.Add(II);
-    Cmp.setOperand(0, II->getArgOperand(0));
-    Cmp.setOperand(1, ConstantInt::get(Ty, C.byteSwap()));
-    return &Cmp;
+    // bswap(A) == C  ->  A == bswap(C)
+    return new ICmpInst(Cmp.getPredicate(), II->getArgOperand(0),
+                        ConstantInt::get(Ty, C.byteSwap()));
 
   case Intrinsic::ctlz:
   case Intrinsic::cttz: {
     // ctz(A) == bitwidth(A)  ->  A == 0 and likewise for !=
-    if (C == BitWidth) {
-      Worklist.Add(II);
-      Cmp.setOperand(0, II->getArgOperand(0));
-      Cmp.setOperand(1, ConstantInt::getNullValue(Ty));
-      return &Cmp;
-    }
+    if (C == BitWidth)
+      return new ICmpInst(Cmp.getPredicate(), II->getArgOperand(0),
+                          ConstantInt::getNullValue(Ty));
 
     // ctz(A) == C -> A & Mask1 == Mask2, where Mask2 only has bit C set
     // and Mask1 has bits 0..C+1 set. Similar for ctl, but for high bits.
@@ -3051,10 +3047,9 @@ Instruction *InstCombiner::foldICmpEqIntrinsicWithConstant(ICmpInst &Cmp,
       APInt Mask2 = IsTrailing
         ? APInt::getOneBitSet(BitWidth, Num)
         : APInt::getOneBitSet(BitWidth, BitWidth - Num - 1);
-      Cmp.setOperand(0, Builder.CreateAnd(II->getArgOperand(0), Mask1));
-      Cmp.setOperand(1, ConstantInt::get(Ty, Mask2));
-      Worklist.Add(II);
-      return &Cmp;
+      return new ICmpInst(Cmp.getPredicate(),
+          Builder.CreateAnd(II->getArgOperand(0), Mask1),
+          ConstantInt::get(Ty, Mask2));
     }
     break;
   }
@@ -3063,14 +3058,10 @@ Instruction *InstCombiner::foldICmpEqIntrinsicWithConstant(ICmpInst &Cmp,
     // popcount(A) == 0  ->  A == 0 and likewise for !=
     // popcount(A) == bitwidth(A)  ->  A == -1 and likewise for !=
     bool IsZero = C.isNullValue();
-    if (IsZero || C == BitWidth) {
-      Worklist.Add(II);
-      Cmp.setOperand(0, II->getArgOperand(0));
-      auto *NewOp =
-          IsZero ? Constant::getNullValue(Ty) : Constant::getAllOnesValue(Ty);
-      Cmp.setOperand(1, NewOp);
-      return &Cmp;
-    }
+    if (IsZero || C == BitWidth)
+      return new ICmpInst(Cmp.getPredicate(), II->getArgOperand(0),
+          IsZero ? Constant::getNullValue(Ty) : Constant::getAllOnesValue(Ty));
+
     break;
   }
 
@@ -3078,9 +3069,7 @@ Instruction *InstCombiner::foldICmpEqIntrinsicWithConstant(ICmpInst &Cmp,
     // uadd.sat(a, b) == 0  ->  (a | b) == 0
     if (C.isNullValue()) {
       Value *Or = Builder.CreateOr(II->getArgOperand(0), II->getArgOperand(1));
-      return replaceInstUsesWith(Cmp, Builder.CreateICmp(
-          Cmp.getPredicate(), Or, Constant::getNullValue(Ty)));
-
+      return new ICmpInst(Cmp.getPredicate(), Or, Constant::getNullValue(Ty));
     }
     break;
   }
@@ -3090,8 +3079,7 @@ Instruction *InstCombiner::foldICmpEqIntrinsicWithConstant(ICmpInst &Cmp,
     if (C.isNullValue()) {
       ICmpInst::Predicate NewPred = Cmp.getPredicate() == ICmpInst::ICMP_EQ
           ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_UGT;
-      return ICmpInst::Create(Instruction::ICmp, NewPred,
-                              II->getArgOperand(0), II->getArgOperand(1));
+      return new ICmpInst(NewPred, II->getArgOperand(0), II->getArgOperand(1));
     }
     break;
   }