Attributor: Propagate align to atomicrmw instructions

[arsenm]

Partially fixes #134480

[arsenm]

• Attributor: Propagate align to cmpxchg instructions #134838
• Attributor: Propagate align to atomicrmw instructions #134837 👈 (View in Graphite)
• Attributor: Add baseline tests for propagating align to atomics #134836
• main

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[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: Matt Arsenault (arsenm)

Changes

Partially fixes #134480

---

Full diff: https://github.com/llvm/llvm-project/pull/134837.diff

2 Files Affected:

• (modified) llvm/lib/Transforms/IPO/AttributorAttributes.cpp (+15-5)
• (modified) llvm/test/Transforms/Attributor/align-atomic.ll (+1-1)

diff --git a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
index a477c90bb4f45..717ba7f688548 100644
--- a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
+++ b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
@@ -5283,7 +5283,7 @@ struct AAAlignImpl : AAAlign {
 
   /// See AbstractAttribute::manifest(...).
   ChangeStatus manifest(Attributor &A) override {
-    ChangeStatus LoadStoreChanged = ChangeStatus::UNCHANGED;
+    ChangeStatus InstrChanged = ChangeStatus::UNCHANGED;
 
     // Check for users that allow alignment annotations.
     Value &AssociatedValue = getAssociatedValue();
@@ -5297,7 +5297,7 @@ struct AAAlignImpl : AAAlign {
             STATS_DECLTRACK(AAAlign, Store,
                             "Number of times alignment added to a store");
             SI->setAlignment(getAssumedAlign());
-            LoadStoreChanged = ChangeStatus::CHANGED;
+            InstrChanged = ChangeStatus::CHANGED;
           }
       } else if (auto *LI = dyn_cast<LoadInst>(U.getUser())) {
         if (LI->getPointerOperand() == &AssociatedValue)
@@ -5305,8 +5305,18 @@ struct AAAlignImpl : AAAlign {
             LI->setAlignment(getAssumedAlign());
             STATS_DECLTRACK(AAAlign, Load,
                             "Number of times alignment added to a load");
-            LoadStoreChanged = ChangeStatus::CHANGED;
+            InstrChanged = ChangeStatus::CHANGED;
           }
+      } else if (auto *RMW = dyn_cast<AtomicRMWInst>(U.getUser())) {
+        if (RMW->getPointerOperand() == &AssociatedValue) {
+          if (RMW->getAlign() < getAssumedAlign()) {
+            STATS_DECLTRACK(AAAlign, AtomicRMW,
+                            "Number of times alignment added to atomicrmw");
+
+            RMW->setAlignment(getAssumedAlign());
+            InstrChanged = ChangeStatus::CHANGED;
+          }
+        }
       }
     }
 
@@ -5315,8 +5325,8 @@ struct AAAlignImpl : AAAlign {
     Align InheritAlign =
         getAssociatedValue().getPointerAlignment(A.getDataLayout());
     if (InheritAlign >= getAssumedAlign())
-      return LoadStoreChanged;
-    return Changed | LoadStoreChanged;
+      return InstrChanged;
+    return Changed | InstrChanged;
   }
 
   // TODO: Provide a helper to determine the implied ABI alignment and check in
diff --git a/llvm/test/Transforms/Attributor/align-atomic.ll b/llvm/test/Transforms/Attributor/align-atomic.ll
index 764ed7419a079..0931c14685a87 100644
--- a/llvm/test/Transforms/Attributor/align-atomic.ll
+++ b/llvm/test/Transforms/Attributor/align-atomic.ll
@@ -16,7 +16,7 @@ define i32 @atomicrmw_add_no_op(ptr align 4 %ptr, i32 %val) {
 define i32 @atomicrmw_add_propagate(ptr align 8 %ptr, i32 %val) {
 ; CHECK-LABEL: define i32 @atomicrmw_add_propagate(
 ; CHECK-SAME: ptr nofree noundef nonnull align 8 captures(none) dereferenceable(4) [[PTR:%.*]], i32 [[VAL:%.*]]) #[[ATTR0]] {
-; CHECK-NEXT:    [[RESULT:%.*]] = atomicrmw add ptr [[PTR]], i32 [[VAL]] seq_cst, align 2
+; CHECK-NEXT:    [[RESULT:%.*]] = atomicrmw add ptr [[PTR]], i32 [[VAL]] seq_cst, align 8
 ; CHECK-NEXT:    ret i32 [[RESULT]]
 ;
   %result = atomicrmw add ptr %ptr, i32 %val seq_cst, align 2

[arsenm]

Merge activity

• Apr 8, 11:01 AM EDT: A user started a stack merge that includes this pull request via Graphite.
• Apr 8, 11:08 AM EDT: Graphite rebased this pull request as part of a merge.
• Apr 8, 11:12 AM EDT: A user merged this pull request with Graphite.