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Throttle the non-local dependence analysis for basic blocks with more than 50 predecessors. Added command line option to play with this threshold.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46790 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tanya Lattner 2008-02-06 00:54:55 +00:00
parent 5c4fb22809
commit 63aa160b27
1 changed files with 20 additions and 7 deletions
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27
lib/Analysis/MemoryDependenceAnalysis.cpp
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@ -20,6 +20,7 @@
#include "llvm/Function.h" #include "llvm/Function.h"
#include "llvm/Analysis/AliasAnalysis.h" #include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Support/CFG.h" #include "llvm/Support/CFG.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Target/TargetData.h" #include "llvm/Target/TargetData.h"
#include "llvm/ADT/Statistic.h" #include "llvm/ADT/Statistic.h"
@ -27,6 +28,15 @@
using namespace llvm; using namespace llvm;
namespace {
// Control the calculation of non-local dependencies by only examining the
// predecessors if the basic block has less than X amount (50 by default).
cl::opt<int>
PredLimit("nonlocaldep-threshold", cl::Hidden, cl::init(50),
cl::desc("Control the calculation of non-local"
"dependencies (default = 50)"));
}
STATISTIC(NumCacheNonlocal, "Number of cached non-local responses"); STATISTIC(NumCacheNonlocal, "Number of cached non-local responses");
STATISTIC(NumUncacheNonlocal, "Number of uncached non-local responses"); STATISTIC(NumUncacheNonlocal, "Number of uncached non-local responses");
@ -211,15 +221,18 @@ void MemoryDependenceAnalysis::nonLocalHelper(Instruction* query,
} }
// If we didn't find anything, recurse on the precessors of this block // If we didn't find anything, recurse on the precessors of this block
// Only do this for blocks with a small number of predecessors.
bool predOnStack = false; bool predOnStack = false;
bool inserted = false; bool inserted = false;
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); if (std::distance(pred_begin(BB), pred_end(BB)) <= PredLimit) {
PI != PE; ++PI) for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
if (!visited.count(*PI)) { PI != PE; ++PI)
stack.push_back(*PI); if (!visited.count(*PI)) {
inserted = true; stack.push_back(*PI);
} else inserted = true;
predOnStack = true; } else
predOnStack = true;
}
// If we inserted a new predecessor, then we'll come back to this block // If we inserted a new predecessor, then we'll come back to this block
if (inserted) if (inserted)