Re: [llvm-commits] [llvm] r46790 - /llvm/trunk/lib/Analysis/MemoryDependenceAnalysis.cpp

[Owen Anderson]

Wow, that must be one hell of a CFG you're dealing with. ;-)

--Owen

On Feb 5, 2008, at 6:54 PM, Tanya Lattner wrote:

Author: tbrethou
Date: Tue Feb  5 18:54:55 2008
New Revision: 46790

URL: http://llvm.org/viewvc/llvm-project?rev=46790&view=rev
Log:


Modified:
   llvm/trunk/lib/Analysis/MemoryDependenceAnalysis.cpp

Modified: llvm/trunk/lib/Analysis/MemoryDependenceAnalysis.cpp
URL: 
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/MemoryDependenceAnalysis.cpp?rev=46790&r1=46789&r2=46790&view=diff


--- llvm/trunk/lib/Analysis/MemoryDependenceAnalysis.cpp (original)

@@ -20,6 +20,7 @@
#include "llvm/Function.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Support/CFG.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Target/TargetData.h"
#include "llvm/ADT/Statistic.h"

@@ -27,6 +28,15 @@

using namespace llvm;

+namespace {

+  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");


@@ -211,15 +221,18 @@
    }


+    // Only do this for blocks with a small number of predecessors.
    bool predOnStack = false;
    bool inserted = false;
-    for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
-         PI != PE; ++PI)
-      if (!visited.count(*PI)) {
-        stack.push_back(*PI);
-        inserted = true;
-      } else
-        predOnStack = true;
+    if (std::distance(pred_begin(BB), pred_end(BB)) <= PredLimit) {
+      for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
+           PI != PE; ++PI)
+        if (!visited.count(*PI)) {
+          stack.push_back(*PI);
+          inserted = true;
+        } else
+          predOnStack = true;
+    }


    if (inserted)


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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. = = = = = = = = ====================================================================== +++ llvm/trunk/lib/Analysis/MemoryDependenceAnalysis.cpp Tue Feb 5 18:54:55 2008 + // Control the calculation of non-local dependencies by only examining the + // predecessors if the basic block has less than X amount (50 by default). STATISTIC(NumUncacheNonlocal, "Number of uncached non-local responses"); // If we didn't find anything, recurse on the precessors of this block // If we inserted a new predecessor, then we'll come back to this block

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