[ReachingDefAnalysis] Fix management of MBBFrameObjsReachingDefs

llvm/include/llvm/CodeGen/ReachingDefAnalysis.h

@@ -141,12 +141,12 @@ class ReachingDefAnalysis : public MachineFunctionPass {
   DenseMap<MachineInstr *, int> InstIds;
 
   MBBReachingDefsInfo MBBReachingDefs;
+
+  /// MBBFrameObjsReachingDefs[{i, j}] is a list of instruction indices
+  /// (relative to begining of MBB i) that define frame index j in MBB i. This
+  /// is used in answering reaching definition queries.
   using MBBFrameObjsReachingDefsInfo =
-      DenseMap<unsigned, DenseMap<int, SmallVector<int>>>;
-  // MBBFrameObjsReachingDefs[i][j] is a list of instruction indices (relative
-  // to begining of MBB) that define frame index (j +
-  // MF->getFrameInfo().getObjectIndexBegin()) in MBB i. This is used in
-  // answering reaching definition queries.
+      DenseMap<std::pair<unsigned, int>, SmallVector<int>>;
   MBBFrameObjsReachingDefsInfo MBBFrameObjsReachingDefs;
 
   /// Default values are 'nothing happened a long time ago'.

llvm/lib/CodeGen/ReachingDefAnalysis.cpp

@@ -147,16 +147,7 @@ void ReachingDefAnalysis::processDefs(MachineInstr *MI) {
       assert(FrameIndex >= 0 && "Can't handle negative frame indicies yet!");
       if (!isFIDef(*MI, FrameIndex, TII))
         continue;
-      if (MBBFrameObjsReachingDefs.contains(MBBNumber)) {
-        auto Frame2InstrIdx = MBBFrameObjsReachingDefs[MBBNumber];
-        if (Frame2InstrIdx.count(FrameIndex - ObjectIndexBegin) > 0)
-          Frame2InstrIdx[FrameIndex - ObjectIndexBegin].push_back(CurInstr);
-        else
-          Frame2InstrIdx[FrameIndex - ObjectIndexBegin] = {CurInstr};
-      } else {
-        MBBFrameObjsReachingDefs[MBBNumber] = {
-            {FrameIndex - ObjectIndexBegin, {CurInstr}}};
-      }
+      MBBFrameObjsReachingDefs[{MBBNumber, FrameIndex}].push_back(CurInstr);
     }
     if (!isValidRegDef(MO))
       continue;
@@ -347,9 +338,13 @@ int ReachingDefAnalysis::getReachingDef(MachineInstr *MI, Register Reg) const {
   int LatestDef = ReachingDefDefaultVal;
 
   if (Reg.isStack()) {
+    // Check that there was a reaching def.
     int FrameIndex = Reg.stackSlotIndex();
-    for (int Def : MBBFrameObjsReachingDefs.lookup(MBBNumber).lookup(
-             FrameIndex - ObjectIndexBegin)) {
+    auto Lookup = MBBFrameObjsReachingDefs.find({MBBNumber, FrameIndex});
+    if (Lookup == MBBFrameObjsReachingDefs.end())
+      return LatestDef;
+    auto &Defs = Lookup->second;
+    for (int Def : Defs) {
       if (Def >= InstId)
         break;
       DefRes = Def;

llvm/test/CodeGen/RISCV/rda-stack.mir

@@ -149,3 +149,43 @@ body:             |
     $x10 = LD %stack.0, 0 :: (load (s64))
     PseudoRET implicit $x10
 ...
+---
+name:            test4
+tracksRegLiveness: true
+fixedStack:
+  - { id: 0, type: default, offset: 0, size: 4, alignment: 16,
+      isImmutable: true, isAliased: false }
+stack:
+  - { id: 0, name: '', type: default, offset: 0, size: 4, alignment: 4,
+      stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
+  - { id: 1, name: '', type: default, offset: 0, size: 4, alignment: 4,
+      stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
+body:             |
+  ; CHECK: RDA results for test4
+  ; CHECK-NEXT: $x10:{ }
+  ; CHECK-NEXT: %stack.0:{ }
+  ; CHECK-NEXT: 0: SD $x10, %stack.0, 0 :: (store (s64))
+  ; CHECK-EMPTY:
+  ; CHECK-NEXT: $x11:{ }
+  ; CHECK-NEXT: %stack.0:{ 0 }
+  ; CHECK-NEXT: 1: SD $x11, %stack.0, 0 :: (store (s64))
+  ; CHECK-EMPTY:
+  ; CHECK-NEXT: $x10:{ }
+  ; CHECK-NEXT: %stack.1:{ }
+  ; CHECK-NEXT: 2: SD $x10, %stack.1, 0 :: (store (s64))
+  ; CHECK-EMPTY:
+  ; CHECK-NEXT: $x11:{ }
+  ; CHECK-NEXT: %stack.1:{ 2 }
+  ; CHECK-NEXT: 3: SD $x11, %stack.1, 0 :: (store (s64))
+  ; CHECK-EMPTY:
+  ; CHECK-NEXT: 4: PseudoRET
+  bb.0.entry:
+    liveins: $x10, $x11
+    SD $x10, %stack.0, 0 :: (store (s64))
+    SD $x11, %stack.0, 0 :: (store (s64))
+    SD $x10, %stack.1, 0 :: (store (s64))
+    SD $x11, %stack.1, 0 :: (store (s64))
+    PseudoRET
+...