Revert r310869 "[InstSimplify][InstCombine] Modify the interface of decomposeBitTestICmp and use it in the InstSimplify"

Failed to add the two files that moved. And then added an extra change I didn't mean to while trying to fix that. Reverting everything.

llvm-svn: 310873

2 files changed, 109 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/CMakeLists.txt b/llvm/lib/Transforms/Utils/CMakeLists.txt
index 8561ec78b1c..83bc05d0311 100644
--- a/llvm/lib/Transforms/Utils/CMakeLists.txt
+++ b/llvm/lib/Transforms/Utils/CMakeLists.txt
@@ -7,6 +7,7 @@ add_llvm_library(LLVMTransformUtils
   BypassSlowDivision.cpp
   CloneFunction.cpp
   CloneModule.cpp
+  CmpInstAnalysis.cpp
   CodeExtractor.cpp
   CtorUtils.cpp
   DemoteRegToStack.cpp
diff --git a/llvm/lib/Transforms/Utils/CmpInstAnalysis.cpp b/llvm/lib/Transforms/Utils/CmpInstAnalysis.cpp
new file mode 100644
index 00000000000..d9294c49930
--- /dev/null
+++ b/llvm/lib/Transforms/Utils/CmpInstAnalysis.cpp
@@ -0,0 +1,108 @@
+//===- CmpInstAnalysis.cpp - Utils to help fold compares ---------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file holds routines to help analyse compare instructions
+// and fold them into constants or other compare instructions
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/CmpInstAnalysis.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Instructions.h"
+
+using namespace llvm;
+
+unsigned llvm::getICmpCode(const ICmpInst *ICI, bool InvertPred) {
+  ICmpInst::Predicate Pred = InvertPred ? ICI->getInversePredicate()
+                                        : ICI->getPredicate();
+  switch (Pred) {
+      // False -> 0
+    case ICmpInst::ICMP_UGT: return 1;  // 001
+    case ICmpInst::ICMP_SGT: return 1;  // 001
+    case ICmpInst::ICMP_EQ:  return 2;  // 010
+    case ICmpInst::ICMP_UGE: return 3;  // 011
+    case ICmpInst::ICMP_SGE: return 3;  // 011
+    case ICmpInst::ICMP_ULT: return 4;  // 100
+    case ICmpInst::ICMP_SLT: return 4;  // 100
+    case ICmpInst::ICMP_NE:  return 5;  // 101
+    case ICmpInst::ICMP_ULE: return 6;  // 110
+    case ICmpInst::ICMP_SLE: return 6;  // 110
+      // True -> 7
+    default:
+      llvm_unreachable("Invalid ICmp predicate!");
+  }
+}
+
+Value *llvm::getICmpValue(bool Sign, unsigned Code, Value *LHS, Value *RHS,
+                          CmpInst::Predicate &NewICmpPred) {
+  switch (Code) {
+    default: llvm_unreachable("Illegal ICmp code!");
+    case 0: // False.
+      return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 0);
+    case 1: NewICmpPred = Sign ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; break;
+    case 2: NewICmpPred = ICmpInst::ICMP_EQ; break;
+    case 3: NewICmpPred = Sign ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; break;
+    case 4: NewICmpPred = Sign ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; break;
+    case 5: NewICmpPred = ICmpInst::ICMP_NE; break;
+    case 6: NewICmpPred = Sign ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; break;
+    case 7: // True.
+      return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 1);
+  }
+  return nullptr;
+}
+
+bool llvm::PredicatesFoldable(ICmpInst::Predicate p1, ICmpInst::Predicate p2) {
+  return (CmpInst::isSigned(p1) == CmpInst::isSigned(p2)) ||
+         (CmpInst::isSigned(p1) && ICmpInst::isEquality(p2)) ||
+         (CmpInst::isSigned(p2) && ICmpInst::isEquality(p1));
+}
+
+bool llvm::decomposeBitTestICmp(const ICmpInst *I, CmpInst::Predicate &Pred,
+                                Value *&X, Value *&Y, Value *&Z) {
+  ConstantInt *C = dyn_cast<ConstantInt>(I->getOperand(1));
+  if (!C)
+    return false;
+
+  switch (I->getPredicate()) {
+  default:
+    return false;
+  case ICmpInst::ICMP_SLT:
+    // X < 0 is equivalent to (X & SignMask) != 0.
+    if (!C->isZero())
+      return false;
+    Y = ConstantInt::get(I->getContext(), APInt::getSignMask(C->getBitWidth()));
+    Pred = ICmpInst::ICMP_NE;
+    break;
+  case ICmpInst::ICMP_SGT:
+    // X > -1 is equivalent to (X & SignMask) == 0.
+    if (!C->isMinusOne())
+      return false;
+    Y = ConstantInt::get(I->getContext(), APInt::getSignMask(C->getBitWidth()));
+    Pred = ICmpInst::ICMP_EQ;
+    break;
+  case ICmpInst::ICMP_ULT:
+    // X <u 2^n is equivalent to (X & ~(2^n-1)) == 0.
+    if (!C->getValue().isPowerOf2())
+      return false;
+    Y = ConstantInt::get(I->getContext(), -C->getValue());
+    Pred = ICmpInst::ICMP_EQ;
+    break;
+  case ICmpInst::ICMP_UGT:
+    // X >u 2^n-1 is equivalent to (X & ~(2^n-1)) != 0.
+    if (!(C->getValue() + 1).isPowerOf2())
+      return false;
+    Y = ConstantInt::get(I->getContext(), ~C->getValue());
+    Pred = ICmpInst::ICMP_NE;
+    break;
+  }
+
+  X = I->getOperand(0);
+  Z = ConstantInt::getNullValue(C->getType());
+  return true;
+}