[PATCH] [LAA-memchecks 1/3] Split out NumComparisons checks. NFC

[Adam Nemet]

Hi hfinkel, aschwaighofer, nadav,

The check for the number of memchecks will be moved to the client of
this analysis.  Besides allowing for transform-specific thresholds, this
also lets Loop Distribution post-process the memchecks; Loop
Distribution only needs memchecks between pointers of different
partitions.

The motivation for this first patch is to untangle the CanDoRT check
from the NumComparison check before moving the NumComparison part.
CanDoRT means that we couldn't determine the bounds for the pointer.
Note that NumComparison is set independent of this flag.

http://reviews.llvm.org/D8122

Files:
  lib/Analysis/LoopAccessAnalysis.cpp

Index: lib/Analysis/LoopAccessAnalysis.cpp
===================================================================
--- lib/Analysis/LoopAccessAnalysis.cpp
+++ lib/Analysis/LoopAccessAnalysis.cpp
@@ -1080,26 +1080,29 @@
   if (NumComparisons == 0 && NeedRTCheck)
     NeedRTCheck = false;
 
-  // Check that we did not collect too many pointers or found an unsizeable
-  // pointer.
-  if (!CanDoRT || NumComparisons > RuntimeMemoryCheckThreshold) {
-    PtrRtCheck.reset();
-    CanDoRT = false;
-  }
-
-  if (CanDoRT) {
+  // Check that we did not find an unsizeable pointer.
+  if (CanDoRT)
     DEBUG(dbgs() << "LAA: We can perform a memory runtime check if needed.\n");
-  }
-
-  if (NeedRTCheck && !CanDoRT) {
+  else if (NeedRTCheck) {
     emitAnalysis(LoopAccessReport() << "cannot identify array bounds");
     DEBUG(dbgs() << "LAA: We can't vectorize because we can't find " <<
           "the array bounds.\n");
     PtrRtCheck.reset();
     CanVecMem = false;
     return;
   }
 
+  if (NumComparisons > RuntimeMemoryCheckThreshold) {
+    emitAnalysis(LoopAccessReport()
+                 << NumComparisons << " exceeds limit of "
+                 << RuntimeMemoryCheckThreshold
+                 << " dependent memory operations checked at runtime");
+    DEBUG(dbgs() << "LAA: Too many memory checks needed.\n");
+    PtrRtCheck.reset();
+    CanVecMem = false;
+    return;
+  }
+
   PtrRtCheck.Need = NeedRTCheck;
 
   CanVecMem = true;
@@ -1121,17 +1124,22 @@
 
       CanDoRT = Accesses.canCheckPtrAtRT(PtrRtCheck, NumComparisons, SE,
                                          TheLoop, Strides, true);
-      // Check that we did not collect too many pointers or found an unsizeable
-      // pointer.
-      if (!CanDoRT || NumComparisons > RuntimeMemoryCheckThreshold) {
-        if (!CanDoRT && NumComparisons > 0)
-          emitAnalysis(LoopAccessReport()
-                       << "cannot check memory dependencies at runtime");
-        else
-          emitAnalysis(LoopAccessReport()
-                       << NumComparisons << " exceeds limit of "
-                       << RuntimeMemoryCheckThreshold
-                       << " dependent memory operations checked at runtime");
+      // Check that we didn't find an unsizeable pointer.
+      if (!CanDoRT && NumComparisons > 0) {
+        emitAnalysis(LoopAccessReport()
+                     << "cannot check memory dependencies at runtime");
+        DEBUG(dbgs() << "LAA: Can't vectorize with memory checks\n");
+        PtrRtCheck.reset();
+        CanVecMem = false;
+        return;
+      }
+
+      // Check that we did not collect too many pointers.
+      if (NumComparisons > RuntimeMemoryCheckThreshold) {
+        emitAnalysis(LoopAccessReport()
+                     << NumComparisons << " exceeds limit of "
+                     << RuntimeMemoryCheckThreshold
+                     << " dependent memory operations checked at runtime");
         DEBUG(dbgs() << "LAA: Can't vectorize with memory checks\n");
         PtrRtCheck.reset();
         CanVecMem = false;

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