[llvm] 275baed - [LAA] Consider accessed addrspace when mapping underlying obj to access. (#129087)

[via llvm-commits]

Author: Florian Hahn
Date: 2025-02-28T20:56:12Z
New Revision: 275baedfde9dcd344bc4f11f552b046a69a4bf3f

URL: https://github.com/llvm/llvm-project/commit/275baedfde9dcd344bc4f11f552b046a69a4bf3f
DIFF: https://github.com/llvm/llvm-project/commit/275baedfde9dcd344bc4f11f552b046a69a4bf3f.diff

LOG: [LAA] Consider accessed addrspace when mapping underlying obj to access. (#129087)

In some cases, it is possible for the same underlying object to be
accessed via pointers to different address spaces. This could lead to
pointers from different address spaces ending up in the same dependency
set, which isn't allowed (and triggers an assertion).

Update the mapping from underlying object -> last access to also include
the accessing address space.

Fixes https://github.com/llvm/llvm-project/issues/124759.

PR: https://github.com/llvm/llvm-project/pull/129087

Added: 
    llvm/test/Analysis/LoopAccessAnalysis/underlying-object-different-address-spaces.ll

Modified: 
    llvm/lib/Analysis/LoopAccessAnalysis.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index cf3bb6a8eae1c..38ee82b77a946 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -1362,8 +1362,10 @@ void AccessAnalysis::processMemAccesses() {
 
     bool SetHasWrite = false;
 
-    // Map of pointers to last access encountered.
-    typedef DenseMap<const Value*, MemAccessInfo> UnderlyingObjToAccessMap;
+    // Map of (pointer to underlying objects, accessed address space) to last
+    // access encountered.
+    typedef DenseMap<std::pair<const Value *, unsigned>, MemAccessInfo>
+        UnderlyingObjToAccessMap;
     UnderlyingObjToAccessMap ObjToLastAccess;
 
     // Set of access to check after all writes have been processed.
@@ -1443,8 +1445,10 @@ void AccessAnalysis::processMemAccesses() {
                     UnderlyingObj->getType()->getPointerAddressSpace()))
               continue;
 
-            auto [It, Inserted] =
-                ObjToLastAccess.try_emplace(UnderlyingObj, Access);
+            auto [It, Inserted] = ObjToLastAccess.try_emplace(
+                {UnderlyingObj,
+                 cast<PointerType>(Ptr->getType())->getAddressSpace()},
+                Access);
             if (!Inserted) {
               DepCands.unionSets(Access, It->second);
               It->second = Access;

diff  --git a/llvm/test/Analysis/LoopAccessAnalysis/underlying-object-
diff erent-address-spaces.ll b/llvm/test/Analysis/LoopAccessAnalysis/underlying-object-
diff erent-address-spaces.ll
new file mode 100644
index 0000000000000..adf73c091be00
--- /dev/null
+++ b/llvm/test/Analysis/LoopAccessAnalysis/underlying-object-
diff erent-address-spaces.ll
@@ -0,0 +1,39 @@
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes='print<access-info>' -disable-output %s 2>&1 | FileCheck %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+
+; Test case for https://github.com/llvm/llvm-project/issues/124759. The same
+; underlying object is access through pointers with 
diff erent address spaces.
+define void @same_underlying_object_
diff erent_address_spaces(ptr %dst1.as1, ptr %dst2.as1) {
+; CHECK-LABEL: 'same_underlying_object_
diff erent_address_spaces'
+; CHECK-NEXT:    loop:
+; CHECK-NEXT:      Report: cannot identify array bounds
+; CHECK-NEXT:      Dependences:
+; CHECK-NEXT:      Run-time memory checks:
+; CHECK-NEXT:      Grouped accesses:
+; CHECK-EMPTY:
+; CHECK-NEXT:      Non vectorizable stores to invariant address were not found in loop.
+; CHECK-NEXT:      SCEV assumptions:
+; CHECK-EMPTY:
+; CHECK-NEXT:      Expressions re-written:
+;
+entry:
+  %alloc = alloca i8, i64 0, align 128
+  %as3 = addrspacecast ptr %alloc to ptr addrspace(3)
+  %as4 = addrspacecast ptr %alloc to ptr addrspace(4)
+  br label %loop
+
+loop:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+  store i32 0, ptr addrspace(4) %as4, align 4
+  store i32 0, ptr %dst1.as1, align 4
+  %l = load i64, ptr addrspace(3) %as3, align 4
+  store i64 %l, ptr %dst2.as1, align 4
+  %iv.next = add i64 %iv, 1
+  %c = icmp eq i64 %iv.next, 100
+  br i1 %c, label %loop, label %exit
+
+exit:
+  ret void
+}