[llvm-commits] [llvm] r44643 - /llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp

[Evan Cheng]

On Dec 5, 2007, at 4:08 PM, Chris Lattner wrote:

> On Dec 5, 2007, at 3:58 PM, Evan Cheng wrote:
>> URL: http://llvm.org/viewvc/llvm-project?rev=44643&view=rev
>> Log:
>> If both result of the {s|z}xt and its source are live out, rewrite
>> all uses of the source with result of extension.
>
> I assume this is experimental, right?  What sort of case does it
> fix?  Testcase please :)

It's experimental. I'll reduce some a test case when it's enabled. :-)

Evan

>
>
> -Chris
>
>> Modified:
>>    llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
>>
>> Modified: llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/
>> Scalar/CodeGenPrepare.cpp?rev=44643&r1=44642&r2=44643&view=diff
>>
>> =
>> =====================================================================
>> ========
>> --- llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp (original)
>> +++ llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp Wed Dec  5
>> 17:58:20 2007
>> @@ -28,11 +28,17 @@
>> #include "llvm/Transforms/Utils/Local.h"
>> #include "llvm/ADT/DenseMap.h"
>> #include "llvm/ADT/SmallSet.h"
>> -#include "llvm/Support/Debug.h"
>> +#include "llvm/Support/CommandLine.h"
>> #include "llvm/Support/Compiler.h"
>> +#include "llvm/Support/Debug.h"
>> #include "llvm/Support/GetElementPtrTypeIterator.h"
>> using namespace llvm;
>>
>> +namespace {
>> +  cl::opt<bool> OptExtUses("optimize-ext-uses",
>> +                           cl::init(false), cl::Hidden);
>> +}
>> +
>> namespace {
>>   class VISIBILITY_HIDDEN CodeGenPrepare : public FunctionPass {
>>     /// TLI - Keep a pointer of a TargetLowering to consult for
>> determining
>> @@ -52,6 +58,7 @@
>>     bool OptimizeLoadStoreInst(Instruction *I, Value *Addr,
>>                                const Type *AccessTy,
>>                                DenseMap<Value*,Value*> &SunkAddrs);
>> +    bool OptimizeExtUses(Instruction *I);
>>   };
>> }
>>
>> @@ -913,6 +920,61 @@
>>   return true;
>> }
>>
>> +bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
>> +  BasicBlock *DefBB = I->getParent();
>> +
>> +  // If both result of the {s|z}xt and its source are live out,
>> rewrite all
>> +  // other uses of the source with result of extension.
>> +  Value *Src = I->getOperand(0);
>> +  if (Src->hasOneUse())
>> +    return false;
>> +
>> +  bool DefIsLiveOut = false;
>> +  for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
>> +       UI != E; ++UI) {
>> +    Instruction *User = cast<Instruction>(*UI);
>> +
>> +    // Figure out which BB this ext is used in.
>> +    BasicBlock *UserBB = User->getParent();
>> +    if (UserBB == DefBB) continue;
>> +    DefIsLiveOut = true;
>> +    break;
>> +  }
>> +  if (!DefIsLiveOut)
>> +    return false;
>> +
>> +  // InsertedTruncs - Only insert one trunc in each block once.
>> +  DenseMap<BasicBlock*, Instruction*> InsertedTruncs;
>> +
>> +  bool MadeChange = false;
>> +  for (Value::use_iterator UI = Src->use_begin(), E = Src- 
>> >use_end();
>> +       UI != E; ++UI) {
>> +    Use &TheUse = UI.getUse();
>> +    Instruction *User = cast<Instruction>(*UI);
>> +
>> +    // Figure out which BB this ext is used in.
>> +    BasicBlock *UserBB = User->getParent();
>> +    if (UserBB == DefBB) continue;
>> +
>> +    // Both src and def are live in this block. Rewrite the use.
>> +    Instruction *&InsertedTrunc = InsertedTruncs[UserBB];
>> +
>> +    if (!InsertedTrunc) {
>> +      BasicBlock::iterator InsertPt = UserBB->begin();
>> +      while (isa<PHINode>(InsertPt)) ++InsertPt;
>> +
>> +      InsertedTrunc = new TruncInst(I, Src->getType(), "",  
>> InsertPt);
>> +    }
>> +
>> +    // Replace a use of the {s|z}ext source with a use of the  
>> result.
>> +    TheUse = InsertedTrunc;
>> +
>> +    MadeChange = true;
>> +  }
>> +
>> +  return MadeChange;
>> +}
>> +
>> // In this pass we look for GEP and cast instructions that are used
>> // across basic blocks and rewrite them to improve basic-block-at-
>> a-time
>> // selection.
>> @@ -948,8 +1010,14 @@
>>       if (isa<Constant>(CI->getOperand(0)))
>>         continue;
>>
>> -      if (TLI)
>> -        MadeChange |= OptimizeNoopCopyExpression(CI, *TLI);
>> +      bool Change = false;
>> +      if (TLI) {
>> +        Change = OptimizeNoopCopyExpression(CI, *TLI);
>> +        MadeChange |= Change;
>> +      }
>> +
>> +      if (OptExtUses && !Change && (isa<ZExtInst>(I) ||
>> isa<SExtInst>(I)))
>> +        MadeChange |= OptimizeExtUses(I);
>>     } else if (CmpInst *CI = dyn_cast<CmpInst>(I)) {
>>       MadeChange |= OptimizeCmpExpression(CI);
>>     } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
>>
>>
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