llvm/lib/Target/Hexagon/HexagonRemoveSZExtArgs.cpp
Chandler Carruth 36b699f2b1 [C++11] Add range based accessors for the Use-Def chain of a Value.
This requires a number of steps.
1) Move value_use_iterator into the Value class as an implementation
   detail
2) Change it to actually be a *Use* iterator rather than a *User*
   iterator.
3) Add an adaptor which is a User iterator that always looks through the
   Use to the User.
4) Wrap these in Value::use_iterator and Value::user_iterator typedefs.
5) Add the range adaptors as Value::uses() and Value::users().
6) Update *all* of the callers to correctly distinguish between whether
   they wanted a use_iterator (and to explicitly dig out the User when
   needed), or a user_iterator which makes the Use itself totally
   opaque.

Because #6 requires churning essentially everything that walked the
Use-Def chains, I went ahead and added all of the range adaptors and
switched them to range-based loops where appropriate. Also because the
renaming requires at least churning every line of code, it didn't make
any sense to split these up into multiple commits -- all of which would
touch all of the same lies of code.

The result is still not quite optimal. The Value::use_iterator is a nice
regular iterator, but Value::user_iterator is an iterator over User*s
rather than over the User objects themselves. As a consequence, it fits
a bit awkwardly into the range-based world and it has the weird
extra-dereferencing 'operator->' that so many of our iterators have.
I think this could be fixed by providing something which transforms
a range of T&s into a range of T*s, but that *can* be separated into
another patch, and it isn't yet 100% clear whether this is the right
move.

However, this change gets us most of the benefit and cleans up
a substantial amount of code around Use and User. =]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203364 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-09 03:16:01 +00:00

90 lines
2.7 KiB
C++

//===- HexagonRemoveExtendArgs.cpp - Remove unnecessary argument sign extends //
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Pass that removes sign extends for function parameters. These parameters
// are already sign extended by the caller per Hexagon's ABI
//
//===----------------------------------------------------------------------===//
#include "Hexagon.h"
#include "HexagonTargetMachine.h"
#include "llvm/CodeGen/MachineFunctionAnalysis.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Scalar.h"
using namespace llvm;
namespace llvm {
void initializeHexagonRemoveExtendArgsPass(PassRegistry&);
}
namespace {
struct HexagonRemoveExtendArgs : public FunctionPass {
public:
static char ID;
HexagonRemoveExtendArgs() : FunctionPass(ID) {
initializeHexagonRemoveExtendArgsPass(*PassRegistry::getPassRegistry());
}
virtual bool runOnFunction(Function &F);
const char *getPassName() const {
return "Remove sign extends";
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<MachineFunctionAnalysis>();
AU.addPreserved<MachineFunctionAnalysis>();
AU.addPreserved("stack-protector");
FunctionPass::getAnalysisUsage(AU);
}
};
}
char HexagonRemoveExtendArgs::ID = 0;
INITIALIZE_PASS(HexagonRemoveExtendArgs, "reargs",
"Remove Sign and Zero Extends for Args", false, false)
bool HexagonRemoveExtendArgs::runOnFunction(Function &F) {
unsigned Idx = 1;
for (Function::arg_iterator AI = F.arg_begin(), AE = F.arg_end(); AI != AE;
++AI, ++Idx) {
if (F.getAttributes().hasAttribute(Idx, Attribute::SExt)) {
Argument* Arg = AI;
if (!isa<PointerType>(Arg->getType())) {
for (auto UI = Arg->user_begin(); UI != Arg->user_end();) {
if (isa<SExtInst>(*UI)) {
Instruction* I = cast<Instruction>(*UI);
SExtInst* SI = new SExtInst(Arg, I->getType());
assert (EVT::getEVT(SI->getType()) ==
(EVT::getEVT(I->getType())));
++UI;
I->replaceAllUsesWith(SI);
Instruction* First = F.getEntryBlock().begin();
SI->insertBefore(First);
I->eraseFromParent();
} else {
++UI;
}
}
}
}
}
return true;
}
FunctionPass*
llvm::createHexagonRemoveExtendArgs(const HexagonTargetMachine &TM) {
return new HexagonRemoveExtendArgs();
}