From 83d99ef4286374e8c41b598f9c6067ee8f942dad Mon Sep 17 00:00:00 2001
From: Fred Chow <fred.chow@yandex.com>
Date: Wed, 19 Jan 2022 16:40:03 -0800
Subject: [PATCH] added fully-available analysis and insert restores as late as
 possible as long as the occ is fully available

When restore is inside infinite loop, set restoreAtEpilog to true.
---
 src/mapleall/maple_be/include/cg/cg_ssu_pre.h |  3 ++
 src/mapleall/maple_be/src/cg/cg_ssu_pre.cpp   | 40 +++++++++++++++----
 2 files changed, 36 insertions(+), 7 deletions(-)

diff --git a/src/mapleall/maple_be/include/cg/cg_ssu_pre.h b/src/mapleall/maple_be/include/cg/cg_ssu_pre.h
index d7e6eef56e..d2bc7c65d0 100644
--- a/src/mapleall/maple_be/include/cg/cg_ssu_pre.h
+++ b/src/mapleall/maple_be/include/cg/cg_ssu_pre.h
@@ -161,6 +161,7 @@ class SSUPre {
         spreMp(memPool),
         spreAllocator(memPool),
         workCand(wkcand),
+        fullyAvailBBs(cgfunc->GetAllBBs().size(), true, spreAllocator.Adapter()),
         realOccDfns(std::less<uint32>(), spreAllocator.Adapter()),
         lambdaDfns(std::less<uint32>(), spreAllocator.Adapter()),
         classCount(0),
@@ -204,6 +205,7 @@ class SSUPre {
     SEntryOcc *entryOcc = spreMp->New<SEntryOcc>(bb);
     entryOccs.push_back(entryOcc);
   }
+  void PropagateNotAvail(BB *bb, std::set<BB*, BBIdCmp> *visitedBBs);
   void FormReals();
 
   CGFunc *cgFunc;
@@ -214,6 +216,7 @@ class SSUPre {
   // following are set of BBs in terms of their dfn's; index into
   // dominance->pdt_preorder to get their bbid's
   // step 0
+  MapleVector<bool> fullyAvailBBs; // index is BBid; true if occ is fully available at BB exit
   MapleSet<uint32> realOccDfns; // set by FormReals()
   // step 1 lambda insertion data structures:
   MapleSet<uint32> lambdaDfns;  // set by FormLambdas()
diff --git a/src/mapleall/maple_be/src/cg/cg_ssu_pre.cpp b/src/mapleall/maple_be/src/cg/cg_ssu_pre.cpp
index 32b910ab5c..46508d2885 100644
--- a/src/mapleall/maple_be/src/cg/cg_ssu_pre.cpp
+++ b/src/mapleall/maple_be/src/cg/cg_ssu_pre.cpp
@@ -36,10 +36,18 @@ void SSUPre::CodeMotion() {
     }
     SRealOcc *realOcc = static_cast<SRealOcc*>(occ);
     if (!realOcc->redundant) {
+      if (realOcc->cgbb->IsWontExit()) {
+        workCand->restoreAtEpilog = true;
+        break;
+      }
       workCand->restoreAtExitBBs.insert(realOcc->cgbb->GetId());
     }
   }
   if (enabledDebug) {
+    if (workCand->restoreAtEpilog) {
+      LogInfo::MapleLogger() << "Giving up because of restore inside infinite loop" << '\n';
+      return;
+    }
     LogInfo::MapleLogger() << " _______ output _______" << '\n';
     LogInfo::MapleLogger() << " restoreAtEntryBBs: [";
     for (uint32 id : workCand->restoreAtEntryBBs) {
@@ -497,18 +505,36 @@ void SSUPre::CreateSortedOccs() {
 
 // ================ Step 0: Preparations ================
 
+void SSUPre::PropagateNotAvail(BB *bb, std::set<BB*, BBIdCmp> *visitedBBs) {
+  if (visitedBBs->count(bb) != 0) {
+    return;
+  }
+  visitedBBs->insert(bb);
+  if (workCand->occBBs.count(bb->GetId()) != 0 ||
+      workCand->saveBBs.count(bb->GetId()) != 0) {
+    return;
+  }
+  fullyAvailBBs[bb->GetId()] = false;
+  for (BB *succbb : bb->GetSuccs()) {
+    PropagateNotAvail(succbb, visitedBBs);
+  }
+}
+
 void SSUPre::FormReals() {
+  std::set<BB*, BBIdCmp> visitedBBs;
+  fullyAvailBBs[cgFunc->GetCommonExitBB()->GetId()] = false;
+  PropagateNotAvail(cgFunc->GetFirstBB(), &visitedBBs);
+
   for (uint32 i = 0; i < pdom->GetPdtPreOrderSize(); i++) {
-    uint32 bbid = pdom->GetPdtPreOrderItem(i);
+    BBId bbid = pdom->GetPdtPreOrderItem(i);
     BB *cgbb = cgFunc->GetAllBBs()[bbid];
-    if (workCand->saveBBs.count(cgbb->GetId()) != 0) {
-      SRealOcc *realOcc = spreMp->New<SRealOcc>(cgbb);
-      realOccs.push_back(realOcc);
-      SKillOcc *killOcc = spreMp->New<SKillOcc>(cgbb);
-      realOccs.push_back(killOcc);
-    } else if (workCand->occBBs.count(cgbb->GetId()) != 0) {
+    if (fullyAvailBBs[cgbb->GetId()]) {
       SRealOcc *realOcc = spreMp->New<SRealOcc>(cgbb);
       realOccs.push_back(realOcc);
+      if (workCand->saveBBs.count(cgbb->GetId()) != 0) {
+        SKillOcc *killOcc = spreMp->New<SKillOcc>(cgbb);
+        realOccs.push_back(killOcc);
+      }
     }
   }
   if (enabledDebug) {
-- 
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