<div dir="ltr">I'd sort of rather have a simple "empty(range)" function that could be applied to any range (equality between iterators should be constant time - it seems unlikely it's ever going to be substantially more expensive to test range.begin() == range.end() than some custom empty implementation for any given sequence) & have more range accessors anywhere they're not already available.<br><br>Not sure what other people think.<br><br>- David</div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Jan 12, 2015 at 7:46 PM, Ramkumar Ramachandra <span dir="ltr"><<a href="mailto:artagnon@gmail.com" target="_blank">artagnon@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: artagnon<br>
Date: Mon Jan 12 21:46:47 2015<br>
New Revision: 225760<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=225760&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=225760&view=rev</a><br>
Log:<br>
Standardize {pred,succ,use,user}_empty()<br>
<br>
The functions {pred,succ,use,user}_{begin,end} exist, but many users<br>
have to check *_begin() with *_end() by hand to determine if the<br>
BasicBlock or User is empty. Fix this with a standard *_empty(),<br>
demonstrating a few usecases.<br>
<br>
Modified:<br>
llvm/trunk/include/llvm/IR/CFG.h<br>
llvm/trunk/include/llvm/IR/Value.h<br>
llvm/trunk/lib/Analysis/CFG.cpp<br>
llvm/trunk/lib/IR/Verifier.cpp<br>
llvm/trunk/lib/Transforms/IPO/PruneEH.cpp<br>
llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp<br>
llvm/trunk/lib/Transforms/Scalar/Reg2Mem.cpp<br>
llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp<br>
<br>
Modified: llvm/trunk/include/llvm/IR/CFG.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/CFG.h?rev=225760&r1=225759&r2=225760&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/CFG.h?rev=225760&r1=225759&r2=225760&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/include/llvm/IR/CFG.h (original)<br>
+++ llvm/trunk/include/llvm/IR/CFG.h Mon Jan 12 21:46:47 2015<br>
@@ -93,6 +93,9 @@ inline pred_iterator pred_end(BasicBlock<br>
inline const_pred_iterator pred_end(const BasicBlock *BB) {<br>
return const_pred_iterator(BB, true);<br>
}<br>
+inline bool pred_empty(const BasicBlock *BB) {<br>
+ return pred_begin(BB) == pred_end(BB);<br>
+}<br>
<br>
<br>
<br>
@@ -257,6 +260,9 @@ inline succ_iterator succ_end(BasicBlock<br>
inline succ_const_iterator succ_end(const BasicBlock *BB) {<br>
return succ_const_iterator(BB->getTerminator(), true);<br>
}<br>
+inline bool succ_empty(const BasicBlock *BB) {<br>
+ return succ_begin(BB) == succ_end(BB);<br>
+}<br>
<br>
template <typename T, typename U> struct isPodLike<SuccIterator<T, U> > {<br>
static const bool value = isPodLike<T>::value;<br>
<br>
Modified: llvm/trunk/include/llvm/IR/Value.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Value.h?rev=225760&r1=225759&r2=225760&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Value.h?rev=225760&r1=225759&r2=225760&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/include/llvm/IR/Value.h (original)<br>
+++ llvm/trunk/include/llvm/IR/Value.h Mon Jan 12 21:46:47 2015<br>
@@ -286,6 +286,8 @@ public:<br>
return iterator_range<const_use_iterator>(use_begin(), use_end());<br>
}<br>
<br>
+ bool user_empty() const { return UseList == nullptr; }<br>
+<br>
typedef user_iterator_impl<User> user_iterator;<br>
typedef user_iterator_impl<const User> const_user_iterator;<br>
user_iterator user_begin() { return user_iterator(UseList); }<br>
<br>
Modified: llvm/trunk/lib/Analysis/CFG.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/CFG.cpp?rev=225760&r1=225759&r2=225760&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/CFG.cpp?rev=225760&r1=225759&r2=225760&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/Analysis/CFG.cpp (original)<br>
+++ llvm/trunk/lib/Analysis/CFG.cpp Mon Jan 12 21:46:47 2015<br>
@@ -27,7 +27,7 @@ using namespace llvm;<br>
void llvm::FindFunctionBackedges(const Function &F,<br>
SmallVectorImpl<std::pair<const BasicBlock*,const BasicBlock*> > &Result) {<br>
const BasicBlock *BB = &F.getEntryBlock();<br>
- if (succ_begin(BB) == succ_end(BB))<br>
+ if (succ_empty(BB))<br>
return;<br>
<br>
SmallPtrSet<const BasicBlock*, 8> Visited;<br>
<br>
Modified: llvm/trunk/lib/IR/Verifier.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Verifier.cpp?rev=225760&r1=225759&r2=225760&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Verifier.cpp?rev=225760&r1=225759&r2=225760&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/IR/Verifier.cpp (original)<br>
+++ llvm/trunk/lib/IR/Verifier.cpp Mon Jan 12 21:46:47 2015<br>
@@ -1128,7 +1128,7 @@ void Verifier::visitFunction(const Funct<br>
<br>
// Check the entry node<br>
const BasicBlock *Entry = &F.getEntryBlock();<br>
- Assert1(pred_begin(Entry) == pred_end(Entry),<br>
+ Assert1(pred_empty(Entry),<br>
"Entry block to function must not have predecessors!", Entry);<br>
<br>
// The address of the entry block cannot be taken, unless it is dead.<br>
<br>
Modified: llvm/trunk/lib/Transforms/IPO/PruneEH.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/PruneEH.cpp?rev=225760&r1=225759&r2=225760&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/PruneEH.cpp?rev=225760&r1=225759&r2=225760&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/Transforms/IPO/PruneEH.cpp (original)<br>
+++ llvm/trunk/lib/Transforms/IPO/PruneEH.cpp Mon Jan 12 21:46:47 2015<br>
@@ -200,7 +200,7 @@ bool PruneEH::SimplifyFunction(Function<br>
BB->getInstList().pop_back();<br>
<br>
// If the unwind block is now dead, nuke it.<br>
- if (pred_begin(UnwindBlock) == pred_end(UnwindBlock))<br>
+ if (pred_empty(UnwindBlock))<br>
DeleteBasicBlock(UnwindBlock); // Delete the new BB.<br>
<br>
++NumRemoved;<br>
@@ -234,7 +234,7 @@ bool PruneEH::SimplifyFunction(Function<br>
/// updating the callgraph to reflect any now-obsolete edges due to calls that<br>
/// exist in the BB.<br>
void PruneEH::DeleteBasicBlock(BasicBlock *BB) {<br>
- assert(pred_begin(BB) == pred_end(BB) && "BB is not dead!");<br>
+ assert(pred_empty(BB) && "BB is not dead!");<br>
CallGraph &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();<br>
<br>
CallGraphNode *CGN = CG[BB->getParent()];<br>
<br>
Modified: llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=225760&r1=225759&r2=225760&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=225760&r1=225759&r2=225760&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp (original)<br>
+++ llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp Mon Jan 12 21:46:47 2015<br>
@@ -188,7 +188,7 @@ bool JumpThreading::runOnFunction(Functi<br>
<br>
// If the block is trivially dead, zap it. This eliminates the successor<br>
// edges which simplifies the CFG.<br>
- if (pred_begin(BB) == pred_end(BB) &&<br>
+ if (pred_empty(BB) &&<br>
BB != &BB->getParent()->getEntryBlock()) {<br>
DEBUG(dbgs() << " JT: Deleting dead block '" << BB->getName()<br>
<< "' with terminator: " << *BB->getTerminator() << '\n');<br>
@@ -662,7 +662,7 @@ static bool hasAddressTakenAndUsed(Basic<br>
bool JumpThreading::ProcessBlock(BasicBlock *BB) {<br>
// If the block is trivially dead, just return and let the caller nuke it.<br>
// This simplifies other transformations.<br>
- if (pred_begin(BB) == pred_end(BB) &&<br>
+ if (pred_empty(BB) &&<br>
BB != &BB->getParent()->getEntryBlock())<br>
return false;<br>
<br>
<br>
Modified: llvm/trunk/lib/Transforms/Scalar/Reg2Mem.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/Reg2Mem.cpp?rev=225760&r1=225759&r2=225760&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/Reg2Mem.cpp?rev=225760&r1=225759&r2=225760&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/Transforms/Scalar/Reg2Mem.cpp (original)<br>
+++ llvm/trunk/lib/Transforms/Scalar/Reg2Mem.cpp Mon Jan 12 21:46:47 2015<br>
@@ -73,7 +73,7 @@ bool RegToMem::runOnFunction(Function &F<br>
<br>
// Insert all new allocas into entry block.<br>
BasicBlock *BBEntry = &F.getEntryBlock();<br>
- assert(pred_begin(BBEntry) == pred_end(BBEntry) &&<br>
+ assert(pred_empty(BBEntry) &&<br>
"Entry block to function must not have predecessors!");<br>
<br>
// Find first non-alloca instruction and create insertion point. This is<br>
<br>
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=225760&r1=225759&r2=225760&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=225760&r1=225759&r2=225760&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)<br>
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Mon Jan 12 21:46:47 2015<br>
@@ -3020,7 +3020,7 @@ bool SimplifyCFGOpt::SimplifyReturn(Retu<br>
}<br>
<br>
// If we eliminated all predecessors of the block, delete the block now.<br>
- if (pred_begin(BB) == pred_end(BB))<br>
+ if (pred_empty(BB))<br>
// We know there are no successors, so just nuke the block.<br>
BB->eraseFromParent();<br>
<br>
@@ -3193,7 +3193,7 @@ bool SimplifyCFGOpt::SimplifyUnreachable<br>
}<br>
<br>
// If this block is now dead, remove it.<br>
- if (pred_begin(BB) == pred_end(BB) &&<br>
+ if (pred_empty(BB) &&<br>
BB != &BB->getParent()->getEntryBlock()) {<br>
// We know there are no successors, so just nuke the block.<br>
BB->eraseFromParent();<br>
@@ -4587,7 +4587,7 @@ bool SimplifyCFGOpt::run(BasicBlock *BB)<br>
<br>
// Remove basic blocks that have no predecessors (except the entry block)...<br>
// or that just have themself as a predecessor. These are unreachable.<br>
- if ((pred_begin(BB) == pred_end(BB) &&<br>
+ if ((pred_emtpy(BB) &&<br>
BB != &BB->getParent()->getEntryBlock()) ||<br>
BB->getSinglePredecessor() == BB) {<br>
DEBUG(dbgs() << "Removing BB: \n" << *BB);<br>
<br>
<br>
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</blockquote></div><br></div>