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