From e511b74f4aa0b74a0d1923beb8b95b966eed2050 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Tue, 14 Nov 2006 07:46:50 +0000
Subject: [PATCH] implement InstCombine/shift-simplify.ll by transforming: (X
 >> Z) op (Y >> Z)  -> (X op Y) >> Z

for all shifts and all ops={and/or/xor}.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31729 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../Scalar/InstructionCombining.cpp           | 49 +++++++++++++++++--
 1 file changed, 46 insertions(+), 3 deletions(-)

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 2e3f9aaa109..80a48605532 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -3310,9 +3310,9 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
   }
 
   // fold (and (cast A), (cast B)) -> (cast (and A, B))
-  if (CastInst *Op0C = dyn_cast<CastInst>(Op0)) {
-    const Type *SrcTy = Op0C->getOperand(0)->getType();
-    if (CastInst *Op1C = dyn_cast<CastInst>(Op1))
+  if (CastInst *Op1C = dyn_cast<CastInst>(Op1)) {
+    if (CastInst *Op0C = dyn_cast<CastInst>(Op0)) {
+      const Type *SrcTy = Op0C->getOperand(0)->getType();
       if (SrcTy == Op1C->getOperand(0)->getType() && SrcTy->isIntegral() &&
           // Only do this if the casts both really cause code to be generated.
           ValueRequiresCast(Op0C->getOperand(0), I.getType(), TD) &&
@@ -3323,6 +3323,21 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
         InsertNewInstBefore(NewOp, I);
         return new CastInst(NewOp, I.getType());
       }
+    }
+  }
+    
+  // (X >> Z) & (Y >> Z)  -> (X&Y) >> Z  for all shifts.
+  if (ShiftInst *SI1 = dyn_cast<ShiftInst>(Op1)) {
+    if (ShiftInst *SI0 = dyn_cast<ShiftInst>(Op0))
+      if (SI0->getOpcode() == SI1->getOpcode() && 
+          SI0->getOperand(1) == SI1->getOperand(1) &&
+          (SI0->hasOneUse() || SI1->hasOneUse())) {
+        Instruction *NewOp =
+          InsertNewInstBefore(BinaryOperator::createAnd(SI0->getOperand(0),
+                                                        SI1->getOperand(0),
+                                                        SI0->getName()), I);
+        return new ShiftInst(SI1->getOpcode(), NewOp, SI1->getOperand(1));
+      }
   }
 
   return Changed ? &I : 0;
@@ -3567,6 +3582,20 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
       }
     }
   }
+  
+  // (X >> Z) | (Y >> Z)  -> (X|Y) >> Z  for all shifts.
+  if (ShiftInst *SI1 = dyn_cast<ShiftInst>(Op1)) {
+    if (ShiftInst *SI0 = dyn_cast<ShiftInst>(Op0))
+      if (SI0->getOpcode() == SI1->getOpcode() && 
+          SI0->getOperand(1) == SI1->getOperand(1) &&
+          (SI0->hasOneUse() || SI1->hasOneUse())) {
+        Instruction *NewOp =
+        InsertNewInstBefore(BinaryOperator::createOr(SI0->getOperand(0),
+                                                     SI1->getOperand(0),
+                                                     SI0->getName()), I);
+        return new ShiftInst(SI1->getOpcode(), NewOp, SI1->getOperand(1));
+      }
+  }
 
   if (match(Op0, m_Not(m_Value(A)))) {   // ~A | Op1
     if (A == Op1)   // ~A | A == -1
@@ -3879,6 +3908,20 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
         return new CastInst(NewOp, I.getType());
       }
   }
+
+  // (X >> Z) ^ (Y >> Z)  -> (X^Y) >> Z  for all shifts.
+  if (ShiftInst *SI1 = dyn_cast<ShiftInst>(Op1)) {
+    if (ShiftInst *SI0 = dyn_cast<ShiftInst>(Op0))
+      if (SI0->getOpcode() == SI1->getOpcode() && 
+          SI0->getOperand(1) == SI1->getOperand(1) &&
+          (SI0->hasOneUse() || SI1->hasOneUse())) {
+        Instruction *NewOp =
+        InsertNewInstBefore(BinaryOperator::createXor(SI0->getOperand(0),
+                                                      SI1->getOperand(0),
+                                                      SI0->getName()), I);
+        return new ShiftInst(SI1->getOpcode(), NewOp, SI1->getOperand(1));
+      }
+  }
     
   return Changed ? &I : 0;
 }