[PATCH] D107964: [LoopIdiom] Don't transform loop into memmove when load from body has more than one use

[Dawid Jurczak via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rGbdcf04246c40: [LoopIdiom] Don't transform loop into memmove when load from body has more than… (authored by yurai007).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D107964/new/

https://reviews.llvm.org/D107964

Files:
  llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
  llvm/test/Transforms/LoopIdiom/basic.ll


Index: llvm/test/Transforms/LoopIdiom/basic.ll
===================================================================
--- llvm/test/Transforms/LoopIdiom/basic.ll
+++ llvm/test/Transforms/LoopIdiom/basic.ll
@@ -1300,14 +1300,10 @@
   ret void
 }
 
-;; FIXME: Do not form memmove when load has more than one use.
+;; Do not form memmove when load has more than one use.
 define i32 @do_not_form_memmove5(i32* %p) {
 ; CHECK-LABEL: @do_not_form_memmove5(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[P2:%.*]] = bitcast i32* [[P:%.*]] to i8*
-; CHECK-NEXT:    [[SCEVGEP:%.*]] = getelementptr i32, i32* [[P:%.*]], i64 1
-; CHECK-NEXT:    [[SCEVGEP1:%.*]] = bitcast i32* [[SCEVGEP]] to i8*
-; CHECK-NEXT:    call void @llvm.memmove.p0i8.p0i8.i64(i8* align 4 [[SCEVGEP1]], i8* align 4 [[P2]], i64 60, i1 false)
 ; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
 ; CHECK:       for.cond.cleanup:
 ; CHECK-NEXT:    [[ADD_LCSSA:%.*]] = phi i32 [ [[ADD:%.*]], [[FOR_BODY]] ]
@@ -1321,6 +1317,7 @@
 ; CHECK-NEXT:    [[TMP1:%.*]] = load i32, i32* [[ARRAYIDX]], align 4
 ; CHECK-NEXT:    [[IDXPROM:%.*]] = zext i32 [[INDEX]] to i64
 ; CHECK-NEXT:    [[ARRAYIDX2:%.*]] = getelementptr inbounds i32, i32* [[P:%.*]], i64 [[IDXPROM]]
+; CHECK-NEXT:    store i32 [[TMP1]], i32* [[ARRAYIDX2]], align 4
 ; CHECK-NEXT:    [[ADD]] = add nsw i32 [[TMP1]], [[SUM:%.*]]
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[INDEX]], 1
 ; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_COND_CLEANUP]]
Index: llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -1318,6 +1318,11 @@
       mayLoopAccessLocation(StoreBasePtr, ModRefInfo::ModRef, CurLoop, BECount,
                             StoreSizeSCEV, *AA, IgnoredInsts);
   if (UseMemMove) {
+    // For memmove case it's not enough to guarantee that loop doesn't access
+    // TheStore and TheLoad. Additionally we need to make sure that TheStore is
+    // the only user of TheLoad.
+    if (!TheLoad->hasOneUse())
+      return Changed;
     IgnoredInsts.insert(TheLoad);
     if (mayLoopAccessLocation(StoreBasePtr, ModRefInfo::ModRef, CurLoop,
                               BECount, StoreSizeSCEV, *AA, IgnoredInsts)) {


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