From 49bdfefc8df5c0073bf716c20400581565644e3f Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Tue, 5 Jan 2010 21:11:17 +0000
Subject: [PATCH] move a trunc-specific transform out of
 commonIntCastTransforms into visitTrunc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92773 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../InstCombine/InstCombineCasts.cpp          | 66 ++++++++++---------
 1 file changed, 34 insertions(+), 32 deletions(-)

diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index 4b8c5534dfa..8a66660e92d 100644
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -625,28 +625,6 @@ Instruction *InstCombiner::commonIntCastTransforms(CastInst &CI) {
     }
   }
   
-  Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
-  Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
-
-  switch (SrcI->getOpcode()) {
-  case Instruction::Add:
-  case Instruction::Mul:
-  case Instruction::And:
-  case Instruction::Or:
-  case Instruction::Xor:
-    // If we are discarding information, rewrite.
-    if (DestBitSize < SrcBitSize && DestBitSize != 1) {
-      // Don't insert two casts unless at least one can be eliminated.
-      if (!ValueRequiresCast(CI.getOpcode(), Op1, DestTy) ||
-          !ValueRequiresCast(CI.getOpcode(), Op0, DestTy)) {
-        Value *Op0c = Builder->CreateTrunc(Op0, DestTy, Op0->getName());
-        Value *Op1c = Builder->CreateTrunc(Op1, DestTy, Op1->getName());
-        return BinaryOperator::Create(
-            cast<BinaryOperator>(SrcI)->getOpcode(), Op0c, Op1c);
-      }
-    }
-    break;
-  }
   return 0;
 }
 
@@ -656,8 +634,8 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
     return Result;
   
   Value *Src = CI.getOperand(0);
-  const Type *Ty = CI.getType();
-  uint32_t DestBitWidth = Ty->getScalarSizeInBits();
+  const Type *DestTy = CI.getType();
+  uint32_t DestBitWidth = DestTy->getScalarSizeInBits();
   uint32_t SrcBitWidth = Src->getType()->getScalarSizeInBits();
 
   // Canonicalize trunc x to i1 -> (icmp ne (and x, 1), 0)
@@ -679,12 +657,12 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
     APInt Mask(APInt::getLowBitsSet(SrcBitWidth, ShAmt).shl(DestBitWidth));
     if (MaskedValueIsZero(ShiftOp, Mask)) {
       if (ShAmt >= DestBitWidth)        // All zeros.
-        return ReplaceInstUsesWith(CI, Constant::getNullValue(Ty));
+        return ReplaceInstUsesWith(CI, Constant::getNullValue(DestTy));
       
       // Okay, we can shrink this.  Truncate the input, then return a new
       // shift.
-      Value *V1 = Builder->CreateTrunc(ShiftOp, Ty, ShiftOp->getName());
-      Value *V2 = ConstantExpr::getTrunc(ShAmtV, Ty);
+      Value *V1 = Builder->CreateTrunc(ShiftOp, DestTy, ShiftOp->getName());
+      Value *V2 = ConstantExpr::getTrunc(ShAmtV, DestTy);
       return BinaryOperator::CreateLShr(V1, V2);
     }
   }
@@ -694,15 +672,39 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
       match(Src, m_Shl(m_Value(ShiftOp), m_ConstantInt(ShAmtV)))) {
     uint32_t ShAmt = ShAmtV->getLimitedValue(SrcBitWidth);
     if (ShAmt >= DestBitWidth)        // All zeros.
-      return ReplaceInstUsesWith(CI, Constant::getNullValue(Ty));
+      return ReplaceInstUsesWith(CI, Constant::getNullValue(DestTy));
       
     // Okay, we can shrink this.  Truncate the input, then return a new
     // shift.
-    Value *V1 = Builder->CreateTrunc(ShiftOp, Ty, ShiftOp->getName());
-    Value *V2 = ConstantExpr::getTrunc(ShAmtV, Ty);
+    Value *V1 = Builder->CreateTrunc(ShiftOp, DestTy, ShiftOp->getName());
+    Value *V2 = ConstantExpr::getTrunc(ShAmtV, DestTy);
     return BinaryOperator::CreateShl(V1, V2);
   }
+  
+  // If we are discarding information from a simple binop, rewrite.
+  if (Src->hasOneUse() && isa<Instruction>(Src)) {
+    Instruction *SrcI = cast<Instruction>(Src);
+    switch (SrcI->getOpcode()) {
+    default: break;
+    case Instruction::Add:
+    // TODO: SUB?
+    case Instruction::Mul:
+    case Instruction::And:
+    case Instruction::Or:
+    case Instruction::Xor:
+      Value *Op0 = SrcI->getOperand(0);
+      Value *Op1 = SrcI->getOperand(1);
 
+      // Don't insert two casts unless at least one can be eliminated.
+      if (!ValueRequiresCast(Instruction::Trunc, Op1, DestTy) ||
+          !ValueRequiresCast(Instruction::Trunc, Op0, DestTy)) {
+        Op0 = Builder->CreateTrunc(Op0, DestTy, Op0->getName());
+        Op1 = Builder->CreateTrunc(Op1, DestTy, Op1->getName());
+        return BinaryOperator::Create(cast<BinaryOperator>(SrcI)->getOpcode(),
+                                      Op0, Op1);
+      }
+    }
+  }
  
   return 0;
 }
@@ -925,8 +927,8 @@ Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
 
   // zext (xor i1 X, true) to i32  --> xor (zext i1 X to i32), 1
   Value *X;
-  if (SrcI && SrcI->getType()->isInteger(1) &&
-      match(SrcI, m_Not(m_Value(X))) && 
+  if (SrcI && SrcI->hasOneUse() && SrcI->getType()->isInteger(1) &&
+      match(SrcI, m_Not(m_Value(X))) &&
       (!X->hasOneUse() || !isa<CmpInst>(X))) {
     Value *New = Builder->CreateZExt(X, CI.getType());
     return BinaryOperator::CreateXor(New, ConstantInt::get(CI.getType(), 1));