[Attributor]: Ensure cycle info is not null when handling PHI in AAPointerInfo (#97321)

Ensure cycle info object is not null for simple PHI case

for the test:
`llvm/test/Transforms/Attributor/phi_bug_pointer_info.ll`

Debug info Before the change: 

```
Accesses by bin after update:
[8-12] : 1
     - 9 -   store i32 %0, ptr %field2, align 4
       - c:   %0 = load i32, ptr %val, align 4
[32-36] : 1
     - 9 -   store i32 %1, ptr %field8, align 4
       - c:   %1 = load i32, ptr %val2, align 4
[2147483647-4294967294] : 1
     - 6 -   %ret = load i32, ptr %x, align 4
       - c: <unknown>
```

Debug info After the change: 

```
Accesses by bin after update:
[8-12] : 2
     - 9 -   store i32 %0, ptr %field2, align 4
       - c:   %0 = load i32, ptr %val, align 4
     - 6 -   %ret = load i32, ptr %x, align 4
       - c: <unknown>
[32-36] : 2
     - 9 -   store i32 %1, ptr %field8, align 4
       - c:   %1 = load i32, ptr %val2, align 4
     - 6 -   %ret = load i32, ptr %x, align 4
       - c: <unknown>
```

Co-authored-by: Vidush Singhal <[email protected]>

Author: vidsinghal

llvm/lib/Transforms/IPO/AttributorAttributes.cpp

@@ -1621,13 +1621,6 @@ ChangeStatus AAPointerInfoFloating::updateImpl(Attributor &A) {
     return true;
   };
 
-  const auto *F = getAnchorScope();
-  const auto *CI =
-      F ? A.getInfoCache().getAnalysisResultForFunction<CycleAnalysis>(*F)
-        : nullptr;
-  const auto *TLI =
-      F ? A.getInfoCache().getTargetLibraryInfoForFunction(*F) : nullptr;
-
   auto UsePred = [&](const Use &U, bool &Follow) -> bool {
     Value *CurPtr = U.get();
     User *Usr = U.getUser();
@@ -1671,18 +1664,18 @@ ChangeStatus AAPointerInfoFloating::updateImpl(Attributor &A) {
     // For PHIs we need to take care of the recurrence explicitly as the value
     // might change while we iterate through a loop. For now, we give up if
     // the PHI is not invariant.
-    if (isa<PHINode>(Usr)) {
+    if (auto *PHI = dyn_cast<PHINode>(Usr)) {
       // Note the order here, the Usr access might change the map, CurPtr is
       // already in it though.
-      bool IsFirstPHIUser = !OffsetInfoMap.count(Usr);
-      auto &UsrOI = OffsetInfoMap[Usr];
+      bool IsFirstPHIUser = !OffsetInfoMap.count(PHI);
+      auto &UsrOI = OffsetInfoMap[PHI];
       auto &PtrOI = OffsetInfoMap[CurPtr];
 
       // Check if the PHI operand has already an unknown offset as we can't
       // improve on that anymore.
       if (PtrOI.isUnknown()) {
         LLVM_DEBUG(dbgs() << "[AAPointerInfo] PHI operand offset unknown "
-                          << *CurPtr << " in " << *Usr << "\n");
+                          << *CurPtr << " in " << *PHI << "\n");
         Follow = !UsrOI.isUnknown();
         UsrOI.setUnknown();
         return true;
@@ -1705,7 +1698,8 @@ ChangeStatus AAPointerInfoFloating::updateImpl(Attributor &A) {
       auto It = OffsetInfoMap.find(CurPtrBase);
       if (It == OffsetInfoMap.end()) {
         LLVM_DEBUG(dbgs() << "[AAPointerInfo] PHI operand is too complex "
-                          << *CurPtr << " in " << *Usr << "\n");
+                          << *CurPtr << " in " << *PHI
+                          << " (base: " << *CurPtrBase << ")\n");
         UsrOI.setUnknown();
         Follow = true;
         return true;
@@ -1718,6 +1712,9 @@ ChangeStatus AAPointerInfoFloating::updateImpl(Attributor &A) {
       // Cycles reported by CycleInfo. It is sufficient to check the PHIs in
       // every Cycle header; if such a node is marked unknown, this will
       // eventually propagate through the whole net of PHIs in the recurrence.
+      const auto *CI =
+          A.getInfoCache().getAnalysisResultForFunction<CycleAnalysis>(
+              *PHI->getFunction());
       if (mayBeInCycle(CI, cast<Instruction>(Usr), /* HeaderOnly */ true)) {
         auto BaseOI = It->getSecond();
         BaseOI.addToAll(Offset.getZExtValue());
@@ -1729,7 +1726,7 @@ ChangeStatus AAPointerInfoFloating::updateImpl(Attributor &A) {
 
         LLVM_DEBUG(
             dbgs() << "[AAPointerInfo] PHI operand pointer offset mismatch "
-                   << *CurPtr << " in " << *Usr << "\n");
+                   << *CurPtr << " in " << *PHI << "\n");
         UsrOI.setUnknown();
         Follow = true;
         return true;
@@ -1882,6 +1879,8 @@ ChangeStatus AAPointerInfoFloating::updateImpl(Attributor &A) {
     if (auto *CB = dyn_cast<CallBase>(Usr)) {
       if (CB->isLifetimeStartOrEnd())
         return true;
+      const auto *TLI =
+          A.getInfoCache().getTargetLibraryInfoForFunction(*CB->getFunction());
       if (getFreedOperand(CB, TLI) == U)
         return true;
       if (CB->isArgOperand(&U)) {

llvm/test/Transforms/Attributor/phi_bug_pointer_info.ll

@@ -0,0 +1,41 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-attributes --check-globals --version 2
+; RUN: opt -aa-pipeline=basic-aa -passes=attributor -debug-only=attributor -attributor-manifest-internal -attributor-annotate-decl-cs  -S < %s 2>&1 | FileCheck %s
+; RUN: opt -aa-pipeline=basic-aa -passes=attributor-cgscc -debug-only=attributor -attributor-manifest-internal -attributor-annotate-decl-cs -S < %s 2>&1 | FileCheck %s
+; REQUIRES: asserts
+
+
+@globalBytes = internal global [1024 x i8] zeroinitializer
+
+; CHECK: Accesses by bin after update:
+; CHECK: [8-12] : 2
+; CHECK:    - 9 -   store i32 %0, ptr %field2, align 4
+; CHECK:      - c:   %0 = load i32, ptr %val, align 4
+; CHECK:    - 6 -   %ret = load i32, ptr %x, align 4
+; CHECK:      - c: <unknown>
+; CHECK: [32-36] : 2
+; CHECK:    - 9 -   store i32 %1, ptr %field8, align 4
+; CHECK:      - c:   %1 = load i32, ptr %val2, align 4
+; CHECK:    - 6 -   %ret = load i32, ptr %x, align 4
+; CHECK:      - c: <unknown>
+define dso_local i32 @phi_different_offsets(ptr nocapture %val, ptr nocapture %val2, i1 %cmp) {
+entry:
+  br i1 %cmp, label %then, label %else
+
+then:
+  %field2 = getelementptr i32, ptr @globalBytes, i32 2
+  %1 = load i32, ptr %val
+  store i32 %1, ptr %field2
+  br label %end
+
+else:
+  %field8 = getelementptr i32, ptr @globalBytes, i32 8
+  %2 = load i32, ptr %val2
+  store i32 %2, ptr %field8
+  br label %end
+
+end:
+  %x = phi ptr [ %field2, %then ], [ %field8, %else ]
+  %ret = load i32, ptr %x
+  ret i32 %ret
+
+}