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Reimplement isPotentiallyReachable to make nocapture deduction much stronger.

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Adds unit tests for it too.

Split BasicBlockUtils into an analysis-half and a transforms-half, and put the
analysis bits into a new Analysis/CFG.{h,cpp}. Promote isPotentiallyReachable
into llvm::isPotentiallyReachable and move it into Analysis/CFG.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187283 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky
2013-07-27 01:24:00 +00:00
parent 332af10901
commit 81e480463d
13 changed files with 666 additions and 142 deletions
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25
lib/Analysis/AliasAnalysis.cpp
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@ -26,6 +26,7 @@
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/CaptureTracking.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/BasicBlock.h"
@ -361,26 +362,6 @@ AliasAnalysis::getModRefInfo(const AtomicRMWInst *RMW, const Location &Loc) {
}
namespace {
/// Determine whether there is a path from From to To within a single
/// function. Returns false only if we can prove that once 'From' has been
/// executed then 'To' can not be executed. Conservatively returns true.
static bool isPotentiallyReachable(const BasicBlock *From,
const BasicBlock *To) {
const unsigned MaxCheck = 5;
const BasicBlock *Current = From;
for (unsigned I = 0; I < MaxCheck; I++) {
unsigned NumSuccs = Current->getTerminator()->getNumSuccessors();
if (NumSuccs > 1)
return true;
if (NumSuccs == 0)
return false;
Current = Current->getTerminator()->getSuccessor(0);
if (Current == To)
return true;
}
return true;
}
/// Only find pointer captures which happen before the given instruction. Uses
/// the dominator tree to determine whether one instruction is before another.
/// Only support the case where the Value is defined in the same basic block
@ -402,7 +383,7 @@ namespace {
// there is no need to explore the use if BeforeHere dominates use.
// Check whether there is a path from I to BeforeHere.
if (BeforeHere != I && DT->dominates(BeforeHere, I) &&
!isPotentiallyReachable(BB, BeforeHere->getParent()))
!isPotentiallyReachable(I, BeforeHere, DT))
return false;
return true;
}
@ -414,7 +395,7 @@ namespace {
if (BeforeHere != I && !DT->isReachableFromEntry(BB))
return false;
if (BeforeHere != I && DT->dominates(BeforeHere, I) &&
!isPotentiallyReachable(BB, BeforeHere->getParent()))
!isPotentiallyReachable(I, BeforeHere, DT))
return false;
Captured = true;
return true;