[LPM] Teach the legacy pass manager to support *using* an analysis

without *requiring* it.

This allows a pass indicate that it will use an analysis if available
(through getAnalysisIfAvailable). When the pass manager knows this, it
will refrain from deleting that analysis if it can. Naturally, it will
still get invalidated at the correct time. These passes are not
considered when scheduling the pass pipeline, so typically they will
require manual scheduling, but this may also allow passes with
getAnalysisIfAvailable to find the analysis more often if nothing after
them requires that analysis and it wasn't invalidated.

I don't have a particular use case with the current passes, but with my
new structure for alias analyses, this will be very useful. We want to
allow people to customize the set of AAs available by scheduling
additional passes. These's aren't ever *required* for obvious reasons.
So we need some way to mark in the legacy pass manager that they will
still be used if available.

This is essentially how analysis groups already work. But this makes the
feature generally available and more explicit. It should allow the AA
change to not impact how people trigger a custom alias analysis being
available at a certain point in compilation.

Differential Revision: http://reviews.llvm.org/D12114

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@245409 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 32 insertions, 16 deletions

diff --git a/lib/IR/LegacyPassManager.cpp b/lib/IR/LegacyPassManager.cpp
index 3ed4adba4c7..5483da1c5e5 100644
--- a/lib/IR/LegacyPassManager.cpp
+++ b/lib/IR/LegacyPassManager.cpp
@@ -989,29 +989,28 @@ void PMDataManager::add(Pass *P, bool ProcessAnalysis) {
 
   // At the moment, this pass is the last user of all required passes.
   SmallVector<Pass *, 12> LastUses;
-  SmallVector<Pass *, 8> RequiredPasses;
+  SmallVector<Pass *, 8> UsedPasses;
   SmallVector<AnalysisID, 8> ReqAnalysisNotAvailable;
 
   unsigned PDepth = this->getDepth();
 
-  collectRequiredAnalysis(RequiredPasses,
-                          ReqAnalysisNotAvailable, P);
-  for (Pass *PRequired : RequiredPasses) {
+  collectRequiredAndUsedAnalyses(UsedPasses, ReqAnalysisNotAvailable, P);
+  for (Pass *PUsed : UsedPasses) {
     unsigned RDepth = 0;
 
-    assert(PRequired->getResolver() && "Analysis Resolver is not set");
-    PMDataManager &DM = PRequired->getResolver()->getPMDataManager();
+    assert(PUsed->getResolver() && "Analysis Resolver is not set");
+    PMDataManager &DM = PUsed->getResolver()->getPMDataManager();
     RDepth = DM.getDepth();
 
     if (PDepth == RDepth)
-      LastUses.push_back(PRequired);
+      LastUses.push_back(PUsed);
     else if (PDepth > RDepth) {
       // Let the parent claim responsibility of last use
-      TransferLastUses.push_back(PRequired);
+      TransferLastUses.push_back(PUsed);
       // Keep track of higher level analysis used by this manager.
-      HigherLevelAnalysis.push_back(PRequired);
+      HigherLevelAnalysis.push_back(PUsed);
     } else
-      llvm_unreachable("Unable to accommodate Required Pass");
+      llvm_unreachable("Unable to accommodate Used Pass");
   }
 
   // Set P as P's last user until someone starts using P.
@@ -1044,22 +1043,27 @@ void PMDataManager::add(Pass *P, bool ProcessAnalysis) {
 }
 
 
-/// Populate RP with analysis pass that are required by
+/// Populate UP with analysis pass that are used or required by
 /// pass P and are available. Populate RP_NotAvail with analysis
 /// pass that are required by pass P but are not available.
-void PMDataManager::collectRequiredAnalysis(SmallVectorImpl<Pass *> &RP,
-                                       SmallVectorImpl<AnalysisID> &RP_NotAvail,
-                                            Pass *P) {
+void PMDataManager::collectRequiredAndUsedAnalyses(
+    SmallVectorImpl<Pass *> &UP, SmallVectorImpl<AnalysisID> &RP_NotAvail,
+    Pass *P) {
   AnalysisUsage *AnUsage = TPM->findAnalysisUsage(P);
+
+  for (const auto &UsedID : AnUsage->getUsedSet())
+    if (Pass *AnalysisPass = findAnalysisPass(UsedID, true))
+      UP.push_back(AnalysisPass);
+
   for (const auto &RequiredID : AnUsage->getRequiredSet())
     if (Pass *AnalysisPass = findAnalysisPass(RequiredID, true))
-      RP.push_back(AnalysisPass);
+      UP.push_back(AnalysisPass);
     else
       RP_NotAvail.push_back(RequiredID);
 
   for (const auto &RequiredID : AnUsage->getRequiredTransitiveSet())
     if (Pass *AnalysisPass = findAnalysisPass(RequiredID, true))
-      RP.push_back(AnalysisPass);
+      UP.push_back(AnalysisPass);
     else
       RP_NotAvail.push_back(RequiredID);
 }
@@ -1196,6 +1200,15 @@ void PMDataManager::dumpPreservedSet(const Pass *P) const {
   dumpAnalysisUsage("Preserved", P, analysisUsage.getPreservedSet());
 }
 
+void PMDataManager::dumpUsedSet(const Pass *P) const {
+  if (PassDebugging < Details)
+    return;
+
+  AnalysisUsage analysisUsage;
+  P->getAnalysisUsage(analysisUsage);
+  dumpAnalysisUsage("Used", P, analysisUsage.getUsedSet());
+}
+
 void PMDataManager::dumpAnalysisUsage(StringRef Msg, const Pass *P,
                                    const AnalysisUsage::VectorType &Set) const {
   assert(PassDebugging >= Details);
@@ -1300,6 +1313,7 @@ bool BBPassManager::runOnFunction(Function &F) {
         dumpPassInfo(BP, MODIFICATION_MSG, ON_BASICBLOCK_MSG,
                      I->getName());
       dumpPreservedSet(BP);
+      dumpUsedSet(BP);
 
       verifyPreservedAnalysis(BP);
       removeNotPreservedAnalysis(BP);
@@ -1514,6 +1528,7 @@ bool FPPassManager::runOnFunction(Function &F) {
     if (LocalChanged)
       dumpPassInfo(FP, MODIFICATION_MSG, ON_FUNCTION_MSG, F.getName());
     dumpPreservedSet(FP);
+    dumpUsedSet(FP);
 
     verifyPreservedAnalysis(FP);
     removeNotPreservedAnalysis(FP);
@@ -1591,6 +1606,7 @@ MPPassManager::runOnModule(Module &M) {
       dumpPassInfo(MP, MODIFICATION_MSG, ON_MODULE_MSG,
                    M.getModuleIdentifier());
     dumpPreservedSet(MP);
+    dumpUsedSet(MP);
 
     verifyPreservedAnalysis(MP);
     removeNotPreservedAnalysis(MP);