[llvm] 2670c7d - [VectorCombine] Fix alignment in single element store

[Qiu Chaofan via llvm-commits]

Author: Qiu Chaofan
Date: 2021-06-11T10:28:15+08:00
New Revision: 2670c7dd5b25e87825edc0aca7729c1d3dba5afc

URL: https://github.com/llvm/llvm-project/commit/2670c7dd5b25e87825edc0aca7729c1d3dba5afc
DIFF: https://github.com/llvm/llvm-project/commit/2670c7dd5b25e87825edc0aca7729c1d3dba5afc.diff

LOG: [VectorCombine] Fix alignment in single element store

This fixes the concern in single element store scalarization that the
alignment of new store may be larger than it should be. It calculates
the largest alignment if index is constant, and a safe one if not.

Reviewed By: lebedev.ri, spatel

Differential Revision: https://reviews.llvm.org/D103419

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/VectorCombine.cpp
    llvm/test/Transforms/VectorCombine/load-insert-store.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
index 66899459bf174..c184c8a08fd0f 100644
--- a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
+++ b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
@@ -831,8 +831,15 @@ bool VectorCombine::foldSingleElementStore(Instruction &I) {
     Builder.Insert(GEP);
     StoreInst *NSI = Builder.CreateStore(NewElement, GEP);
     NSI->copyMetadata(*SI);
-    if (SI->getAlign() < NSI->getAlign())
-      NSI->setAlignment(SI->getAlign());
+    Align NewAlignment = std::max(SI->getAlign(), Load->getAlign());
+    if (auto *C = dyn_cast<ConstantInt>(Idx))
+      NewAlignment = commonAlignment(
+          NewAlignment,
+          C->getZExtValue() * DL.getTypeStoreSize(NewElement->getType()));
+    else
+      NewAlignment = commonAlignment(
+          NewAlignment, DL.getTypeStoreSize(NewElement->getType()));
+    NSI->setAlignment(NewAlignment);
     replaceValue(I, *NSI);
     // Need erasing the store manually.
     I.eraseFromParent();

diff  --git a/llvm/test/Transforms/VectorCombine/load-insert-store.ll b/llvm/test/Transforms/VectorCombine/load-insert-store.ll
index 14f618eceaa3b..6218ecd10c7dc 100644
--- a/llvm/test/Transforms/VectorCombine/load-insert-store.ll
+++ b/llvm/test/Transforms/VectorCombine/load-insert-store.ll
@@ -20,7 +20,7 @@ define void @insert_store_i16_align1(<8 x i16>* %q, i16 zeroext %s) {
 ; CHECK-LABEL: @insert_store_i16_align1(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[TMP0:%.*]] = getelementptr inbounds <8 x i16>, <8 x i16>* [[Q:%.*]], i32 0, i32 3
-; CHECK-NEXT:    store i16 [[S:%.*]], i16* [[TMP0]], align 1
+; CHECK-NEXT:    store i16 [[S:%.*]], i16* [[TMP0]], align 2
 ; CHECK-NEXT:    ret void
 ;
 entry:
@@ -125,6 +125,7 @@ entry:
   ret void
 }
 
+; To verify align here is narrowed to scalar store size
 define void @insert_store_nonconst_large_alignment(<4 x i32>* %q, i32 zeroext %s, i32 %idx) {
 ; CHECK-LABEL: @insert_store_nonconst_large_alignment(
 ; CHECK-NEXT:  entry:
@@ -148,7 +149,7 @@ define void @insert_store_nonconst_align_maximum_8(<8 x i64>* %q, i64 %s, i32 %i
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i32 [[IDX:%.*]], 2
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[CMP]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr inbounds <8 x i64>, <8 x i64>* [[Q:%.*]], i32 0, i32 [[IDX]]
-; CHECK-NEXT:    store i64 [[S:%.*]], i64* [[TMP1]], align 4
+; CHECK-NEXT:    store i64 [[S:%.*]], i64* [[TMP1]], align 8
 ; CHECK-NEXT:    ret void
 ;
   %cmp = icmp ult i32 %idx, 2
@@ -180,7 +181,7 @@ define void @insert_store_nonconst_align_larger(<8 x i64>* %q, i64 %s, i32 %idx)
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i32 [[IDX:%.*]], 2
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[CMP]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr inbounds <8 x i64>, <8 x i64>* [[Q:%.*]], i32 0, i32 [[IDX]]
-; CHECK-NEXT:    store i64 [[S:%.*]], i64* [[TMP1]], align 2
+; CHECK-NEXT:    store i64 [[S:%.*]], i64* [[TMP1]], align 4
 ; CHECK-NEXT:    ret void
 ;
   %cmp = icmp ult i32 %idx, 2