[AA] Support callCapturesBefore() on BatchAA (NFCI)

This is not expected to have any practical compile-time effect,
as the alias() calls inside callCapturesBefore() are rare. This
should still be supported for API completeness, and might be
useful for reachability caching.

Author: nikic

llvm/include/llvm/Analysis/AliasAnalysis.h

@@ -795,7 +795,11 @@ class AAResults {
   /// Early exits in callCapturesBefore may lead to ModRefInfo::Must not being
   /// set.
   ModRefInfo callCapturesBefore(const Instruction *I,
-                                const MemoryLocation &MemLoc, DominatorTree *DT);
+                                const MemoryLocation &MemLoc,
+                                DominatorTree *DT) {
+    AAQueryInfo AAQIP;
+    return callCapturesBefore(I, MemLoc, DT, AAQIP);
+  }
 
   /// A convenience wrapper to synthesize a memory location.
   ModRefInfo callCapturesBefore(const Instruction *I, const Value *P,
@@ -864,6 +868,9 @@ class AAResults {
   ModRefInfo getModRefInfo(const Instruction *I,
                            const Optional<MemoryLocation> &OptLoc,
                            AAQueryInfo &AAQIP);
+  ModRefInfo callCapturesBefore(const Instruction *I,
+                                const MemoryLocation &MemLoc, DominatorTree *DT,
+                                AAQueryInfo &AAQIP);
 
   class Concept;
 
@@ -925,6 +932,11 @@ class BatchAAResults {
                  MemoryLocation(V2, LocationSize::precise(1))) ==
            AliasResult::MustAlias;
   }
+  ModRefInfo callCapturesBefore(const Instruction *I,
+                                const MemoryLocation &MemLoc,
+                                DominatorTree *DT) {
+    return AA.callCapturesBefore(I, MemLoc, DT, AAQI);
+  }
 };
 
 /// Temporary typedef for legacy code that uses a generic \c AliasAnalysis

llvm/lib/Analysis/AliasAnalysis.cpp

@@ -718,7 +718,8 @@ ModRefInfo AAResults::getModRefInfo(const Instruction *I,
 /// with a smarter AA in place, this test is just wasting compile time.
 ModRefInfo AAResults::callCapturesBefore(const Instruction *I,
                                          const MemoryLocation &MemLoc,
-                                         DominatorTree *DT) {
+                                         DominatorTree *DT,
+                                         AAQueryInfo &AAQI) {
   if (!DT)
     return ModRefInfo::ModRef;
 
@@ -749,7 +750,9 @@ ModRefInfo AAResults::callCapturesBefore(const Instruction *I,
          !Call->isByValArgument(ArgNo)))
       continue;
 
-    AliasResult AR = alias(*CI, Object);
+    AliasResult AR = alias(
+        MemoryLocation::getBeforeOrAfter(*CI),
+        MemoryLocation::getBeforeOrAfter(Object), AAQI);
     // If this is a no-capture pointer argument, see if we can tell that it
     // is impossible to alias the pointer we're checking.  If not, we have to
     // assume that the call could touch the pointer, even though it doesn't

llvm/lib/Analysis/MemoryDependenceAnalysis.cpp

@@ -608,8 +608,7 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
     ModRefInfo MR = BatchAA.getModRefInfo(Inst, MemLoc);
     // If necessary, perform additional analysis.
     if (isModAndRefSet(MR))
-      // TODO: Support callCapturesBefore() on BatchAAResults.
-      MR = AA.callCapturesBefore(Inst, MemLoc, &DT);
+      MR = BatchAA.callCapturesBefore(Inst, MemLoc, &DT);
     switch (clearMust(MR)) {
     case ModRefInfo::NoModRef:
       // If the call has no effect on the queried pointer, just ignore it.