[llvm-commits] [llvm] r169079 [1/2] - in /llvm/trunk: lib/Transforms/IPO/GlobalOpt.cpp test/Transforms/GlobalOpt/big-memory-footprint.ll

[Chandler Carruth]

Zhou, this commit was not approved in code review. Please revert and ping
the code review thread until the review concludes with an explicit approval
to commit. Commit after approval is really fundamental to the LLVM
development process, don't circumvent it.


On Fri, Nov 30, 2012 at 8:38 PM, Zhou Sheng <zhousheng00 at gmail.com> wrote:

> Author: sheng
> Date: Fri Nov 30 22:38:53 2012
> New Revision: 169079
>
> URL: http://llvm.org/viewvc/llvm-project?rev=169079&view=rev
> Log:
> The patch is to improve the memory footprint of pass GlobalOpt.
> Also check in a case to repeat the issue, on which 'opt -globalopt'
> consumes 1.6GB memory.
> The big memory footprint cause is that current GlobalOpt one by one hoists
> and stores the leaf element constant into the global array, in each
> iteration, it recreates the global array initializer constant and leave the
> old initializer alone. This may result in many obsolete constants left.
> For example:  we have global array @rom = global [16 x i32] zeroinitializer
> After the first element value is hoisted and installed:   @rom = global
> [16 x i32] [ 1, 0, 0, ... ]
> After the second element value is installed:  @rom = global [16 x 32] [ 1,
> 2, 0, 0, ... ]        // here the previous initializer is obsolete
> ...
> When the transform is done, we have 15 obsolete initializers left useless.
>
> Added:
>     llvm/trunk/test/Transforms/GlobalOpt/big-memory-footprint.ll
> Modified:
>     llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
>
> Modified: llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp?rev=169079&r1=169078&r2=169079&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp (original)
> +++ llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp Fri Nov 30 22:38:53 2012
> @@ -36,6 +36,7 @@
>  #include "llvm/ADT/DenseMap.h"
>  #include "llvm/ADT/SmallPtrSet.h"
>  #include "llvm/ADT/SmallVector.h"
> +#include "llvm/ADT/SetVector.h"
>  #include "llvm/ADT/Statistic.h"
>  #include "llvm/ADT/STLExtras.h"
>  #include <algorithm>
> @@ -2398,7 +2399,8 @@
>  /// initializer.  This returns 'Init' modified to reflect 'Val' stored
> into it.
>  /// At this point, the GEP operands of Addr [0, OpNo) have been stepped
> into.
>  static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
> -                                   ConstantExpr *Addr, unsigned OpNo) {
> +                                   ConstantExpr *Addr, unsigned OpNo,
> +                                   SetVector<Constant*>& Obsolete) {
>    // Base case of the recursion.
>    if (OpNo == Addr->getNumOperands()) {
>      assert(Val->getType() == Init->getType() && "Type mismatch!");
> @@ -2415,7 +2417,9 @@
>      ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
>      unsigned Idx = CU->getZExtValue();
>      assert(Idx < STy->getNumElements() && "Struct index out of range!");
> -    Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
> +    if (Elts[Idx]->getType()->isAggregateType())
> +      Obsolete.insert(Elts[Idx]);
> +    Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1, Obsolete);
>
>      // Return the modified struct.
>      return ConstantStruct::get(STy, Elts);
> @@ -2435,8 +2439,11 @@
>      Elts.push_back(Init->getAggregateElement(i));
>
>    assert(CI->getZExtValue() < NumElts);
> +  Constant *OrigElem = Elts[CI->getZExtValue()];
> +  if (OrigElem->getType()->isAggregateType())
> +    Obsolete.insert(OrigElem);
>    Elts[CI->getZExtValue()] =
> -    EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
> +    EvaluateStoreInto(OrigElem, Val, Addr, OpNo+1, Obsolete);
>
>    if (Init->getType()->isArrayTy())
>      return ConstantArray::get(cast<ArrayType>(InitTy), Elts);
> @@ -2452,9 +2459,20 @@
>      return;
>    }
>
> +  // Collect obsolete constants created in previous CommitValueTo()
> invoke.
> +  SetVector<Constant*> Obsolete;
>    ConstantExpr *CE = cast<ConstantExpr>(Addr);
>    GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
> -  GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2));
> +  Constant *OrigInit = GV->getInitializer();
> +  if (OrigInit->getType()->isAggregateType())
> +    Obsolete.insert(OrigInit);
> +  Constant *Init = EvaluateStoreInto(OrigInit, Val, CE, 2, Obsolete);
> +  GV->setInitializer(Init);
> +
> +  for (unsigned i = 0; i < Obsolete.size(); ++i) {
> +    if (Obsolete[i]->use_empty())
> +      Obsolete[i]->destroyConstant();
> +  }
>  }
>
>  namespace {
>
>
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