[llvm] bb3066d - [LAA] Move scalable vector check into `getStrideFromAddRec()` (#154013)

[via llvm-commits]

Author: Benjamin Maxwell
Date: 2025-08-19T06:40:07+01:00
New Revision: bb3066d42b42a3e6deaf69bcfabf8597018ec44b

URL: https://github.com/llvm/llvm-project/commit/bb3066d42b42a3e6deaf69bcfabf8597018ec44b
DIFF: https://github.com/llvm/llvm-project/commit/bb3066d42b42a3e6deaf69bcfabf8597018ec44b.diff

LOG: [LAA] Move scalable vector check into `getStrideFromAddRec()` (#154013)

This moves the check closer to the `.getFixedValue()` call and fixes
#153797 (which is a regression from #126971).

Added: 
    

Modified: 
    llvm/lib/Analysis/LoopAccessAnalysis.cpp
    llvm/test/Analysis/LoopAccessAnalysis/scalable-vector-regression-tests.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 62baf9b632bc7..bceddd0325276 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -936,6 +936,12 @@ class AccessAnalysis {
 static std::optional<int64_t>
 getStrideFromAddRec(const SCEVAddRecExpr *AR, const Loop *Lp, Type *AccessTy,
                     Value *Ptr, PredicatedScalarEvolution &PSE) {
+  if (isa<ScalableVectorType>(AccessTy)) {
+    LLVM_DEBUG(dbgs() << "LAA: Bad stride - Scalable object: " << *AccessTy
+                      << "\n");
+    return std::nullopt;
+  }
+
   // The access function must stride over the innermost loop.
   if (Lp != AR->getLoop()) {
     LLVM_DEBUG({
@@ -1590,11 +1596,6 @@ llvm::getPtrStride(PredicatedScalarEvolution &PSE, Type *AccessTy, Value *Ptr,
     return 0;
 
   assert(Ptr->getType()->isPointerTy() && "Unexpected non-ptr");
-  if (isa<ScalableVectorType>(AccessTy)) {
-    LLVM_DEBUG(dbgs() << "LAA: Bad stride - Scalable object: " << *AccessTy
-                      << "\n");
-    return std::nullopt;
-  }
 
   const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PtrScev);
   if (Assume && !AR)

diff  --git a/llvm/test/Analysis/LoopAccessAnalysis/scalable-vector-regression-tests.ll b/llvm/test/Analysis/LoopAccessAnalysis/scalable-vector-regression-tests.ll
index ffa5b3c868ab0..4dde864b2f1e2 100644
--- a/llvm/test/Analysis/LoopAccessAnalysis/scalable-vector-regression-tests.ll
+++ b/llvm/test/Analysis/LoopAccessAnalysis/scalable-vector-regression-tests.ll
@@ -61,3 +61,29 @@ vector.body:
 end:
   ret void
 }
+
+; CHECK-LABEL: 'regression_test_is_no_wrap_access_scalable_typesize'
+; CHECK: LAA: Found an analyzable loop: loop
+; CHECK: LAA: Bad stride - Scalable object: <vscale x 4 x i32>
+define void @regression_test_is_no_wrap_access_scalable_typesize(ptr %ptr_a, i64 %n, ptr %ptr_b) {
+entry:
+  br label %loop
+loop:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+  %2 = shl i64 %iv, 1
+  %3 = add i64 %2, %n
+  %4 = trunc i64 %iv to i32
+  %5 = insertelement <vscale x 4 x i32> zeroinitializer, i32 %4, i64 0
+  %6 = getelementptr i32, ptr %ptr_a, i64 %3
+  store <vscale x 4 x i32> %5, ptr %6, align 4
+  %.reass3 = or i32 %4, 1
+  %7 = insertelement <vscale x 4 x i32> zeroinitializer, i32 %.reass3, i64 0
+  %8 = shufflevector <vscale x 4 x i32> %7, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer
+  %9 = getelementptr i32, ptr %ptr_b, i64 %3
+  store <vscale x 4 x i32> %8, ptr %9, align 4
+  %iv.next = add i64 %iv, 1
+  %.not = icmp eq i64 %iv, 16
+  br i1 %.not, label %end, label %loop
+end:
+  ret void
+}