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, 31 insertions, 22 deletions

diff --git a/llvm/lib/Analysis/CMakeLists.txt b/llvm/lib/Analysis/CMakeLists.txt
index 45268dd5c76..161709a4846 100644
--- a/llvm/lib/Analysis/CMakeLists.txt
+++ b/llvm/lib/Analysis/CMakeLists.txt
@@ -18,7 +18,6 @@ add_llvm_library(LLVMAnalysis
   CallGraphSCCPass.cpp
   CallPrinter.cpp
   CaptureTracking.cpp
-  CmpInstAnalysis.cpp
   CostModel.cpp
   CodeMetrics.cpp
   ConstantFolding.cpp
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index d155f6b4803..9729629b167 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -23,7 +23,6 @@
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/AssumptionCache.h"
 #include "llvm/Analysis/CaptureTracking.h"
-#include "llvm/Analysis/CmpInstAnalysis.h"
 #include "llvm/Analysis/ConstantFolding.h"
 #include "llvm/Analysis/LoopAnalysisManager.h"
 #include "llvm/Analysis/MemoryBuiltins.h"
@@ -3621,29 +3620,32 @@ static Value *simplifySelectBitTest(Value *TrueVal, Value *FalseVal, Value *X,
 
 /// An alternative way to test if a bit is set or not uses sgt/slt instead of
 /// eq/ne.
-static Value *simplifySelectWithFakeICmpEq(Value *CmpLHS, Value *CmpRHS,
-                                           ICmpInst::Predicate Pred,
-                                           Value *TrueVal, Value *FalseVal) {
-  Value *X;
-  APInt Mask;
-  if (!decomposeBitTestICmp(CmpLHS, CmpRHS, Pred, X, Mask))
-    return nullptr;
-
+static Value *simplifySelectWithFakeICmpEq(Value *CmpLHS, Value *TrueVal,
+                                           Value *FalseVal,
+                                           bool TrueWhenUnset) {
   unsigned BitWidth = TrueVal->getType()->getScalarSizeInBits();
   if (!BitWidth)
     return nullptr;
 
-  Value *ExtX;
-  if (match(X, m_Trunc(m_Value(ExtX))) &&
-      (ExtX == TrueVal || ExtX == FalseVal)) {
+  APInt MinSignedValue;
+  Value *X;
+  if (match(CmpLHS, m_Trunc(m_Value(X))) && (X == TrueVal || X == FalseVal)) {
     // icmp slt (trunc X), 0  <--> icmp ne (and X, C), 0
     // icmp sgt (trunc X), -1 <--> icmp eq (and X, C), 0
-    X = ExtX;
-    Mask = Mask.zext(BitWidth);
+    unsigned DestSize = CmpLHS->getType()->getScalarSizeInBits();
+    MinSignedValue = APInt::getSignedMinValue(DestSize).zext(BitWidth);
+  } else {
+    // icmp slt X, 0  <--> icmp ne (and X, C), 0
+    // icmp sgt X, -1 <--> icmp eq (and X, C), 0
+    X = CmpLHS;
+    MinSignedValue = APInt::getSignedMinValue(BitWidth);
   }
 
-  return simplifySelectBitTest(TrueVal, FalseVal, X, &Mask,
-                               Pred == ICmpInst::ICMP_EQ);
+  if (Value *V = simplifySelectBitTest(TrueVal, FalseVal, X, &MinSignedValue,
+                                       TrueWhenUnset))
+    return V;
+
+  return nullptr;
 }
 
 /// Try to simplify a select instruction when its condition operand is an
@@ -3656,6 +3658,9 @@ static Value *simplifySelectWithICmpCond(Value *CondVal, Value *TrueVal,
   if (!match(CondVal, m_ICmp(Pred, m_Value(CmpLHS), m_Value(CmpRHS))))
     return nullptr;
 
+  // FIXME: This code is nearly duplicated in InstCombine. Using/refactoring
+  // decomposeBitTestICmp() might help.
+  // FIXME this should support ICMP_SLE/SGE forms as well
   if (ICmpInst::isEquality(Pred) && match(CmpRHS, m_Zero())) {
     Value *X;
     const APInt *Y;
@@ -3663,13 +3668,18 @@ static Value *simplifySelectWithICmpCond(Value *CondVal, Value *TrueVal,
       if (Value *V = simplifySelectBitTest(TrueVal, FalseVal, X, Y,
                                            Pred == ICmpInst::ICMP_EQ))
         return V;
+  } else if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, m_Zero())) {
+    // Comparing signed-less-than 0 checks if the sign bit is set.
+    if (Value *V = simplifySelectWithFakeICmpEq(CmpLHS, TrueVal, FalseVal,
+                                                false))
+      return V;
+  } else if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, m_AllOnes())) {
+    // Comparing signed-greater-than -1 checks if the sign bit is not set.
+    if (Value *V = simplifySelectWithFakeICmpEq(CmpLHS, TrueVal, FalseVal,
+                                                true))
+      return V;
   }
 
-  // Check for other compares that behave like bit test.
-  if (Value *V = simplifySelectWithFakeICmpEq(CmpLHS, CmpRHS, Pred,
-                                              TrueVal, FalseVal))
-    return V;
-
   if (CondVal->hasOneUse()) {
     const APInt *C;
     if (match(CmpRHS, m_APInt(C))) {