[llvm] 46ea4b5 - [LV] Avoid a crash when costing a uniform store which doesn't correspond to a legal scatter

Philip Reames via llvm-commits llvm-commits at lists.llvm.org
Thu Jun 23 12:41:48 PDT 2022


Author: Philip Reames
Date: 2022-06-23T12:41:09-07:00
New Revision: 46ea4b5ea10f9363503b047a2e6a577a8603797d

URL: https://github.com/llvm/llvm-project/commit/46ea4b5ea10f9363503b047a2e6a577a8603797d
DIFF: https://github.com/llvm/llvm-project/commit/46ea4b5ea10f9363503b047a2e6a577a8603797d.diff

LOG: [LV] Avoid a crash when costing a uniform store which doesn't correspond to a legal scatter

If we have an unaligned uniform store, then when costing a scalable VF we can't emit code to scalarize it.  (Well, we could, but we haven't implemented that case.)  This change replaces an assert with a cost-model bailout such that we reject vectorization with the scalable VF instead of crashing.

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    llvm/test/Transforms/LoopVectorize/RISCV/scalable-basics.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 04f4e12a6b04e..4119c62041938 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -6790,8 +6790,6 @@ void LoopVectorizationCostModel::setCostBasedWideningDecision(ElementCount VF) {
           Cost = getGatherScatterCost(&I, VF);
           setWideningDecision(&I, VF, CM_GatherScatter, Cost);
         } else {
-          assert((isa<LoadInst>(&I) || !VF.isScalable()) &&
-                 "Cannot yet scalarize uniform stores");
           Cost = getUniformMemOpCost(&I, VF);
           setWideningDecision(&I, VF, CM_Scalarize, Cost);
         }
@@ -7149,8 +7147,13 @@ LoopVectorizationCostModel::getInstructionCost(Instruction *I, ElementCount VF,
       InstWidening Decision = getWideningDecision(I, Width);
       assert(Decision != CM_Unknown &&
              "CM decision should be taken at this point");
-      if (Decision == CM_Scalarize)
+      if (Decision == CM_Scalarize) {
+        if (VF.isScalable() && isa<StoreInst>(I))
+          // We can't scalarize a scalable vector store (even a uniform one
+          // currently), return an invalid cost so as to prevent vectorization.
+          return InstructionCost::getInvalid();
         Width = ElementCount::getFixed(1);
+      }
     }
     VectorTy = ToVectorTy(getLoadStoreType(I), Width);
     return getMemoryInstructionCost(I, VF);

diff  --git a/llvm/test/Transforms/LoopVectorize/RISCV/scalable-basics.ll b/llvm/test/Transforms/LoopVectorize/RISCV/scalable-basics.ll
index 9af09e4b4ffe6..f7249bd27b001 100644
--- a/llvm/test/Transforms/LoopVectorize/RISCV/scalable-basics.ll
+++ b/llvm/test/Transforms/LoopVectorize/RISCV/scalable-basics.ll
@@ -350,3 +350,240 @@ for.end:
   ret void
 }
 
+define void @uniform_store(ptr noalias nocapture %a, ptr noalias nocapture %b, i64 %v, i64 %n) {
+; CHECK-LABEL: @uniform_store(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
+; CHECK:       vector.ph:
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <2 x i64> poison, i64 [[V:%.*]], i32 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <2 x i64> [[BROADCAST_SPLATINSERT]], <2 x i64> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <2 x i64> poison, i64 [[V]], i32 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT2:%.*]] = shufflevector <2 x i64> [[BROADCAST_SPLATINSERT1]], <2 x i64> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = add i64 [[INDEX]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = add i64 [[INDEX]], 2
+; CHECK-NEXT:    store i64 [[V]], ptr [[B:%.*]], align 8
+; CHECK-NEXT:    store i64 [[V]], ptr [[B]], align 8
+; CHECK-NEXT:    store i64 [[V]], ptr [[B]], align 8
+; CHECK-NEXT:    store i64 [[V]], ptr [[B]], align 8
+; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr inbounds i64, ptr [[A:%.*]], i64 [[TMP0]]
+; CHECK-NEXT:    [[TMP3:%.*]] = getelementptr inbounds i64, ptr [[A]], i64 [[TMP1]]
+; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr inbounds i64, ptr [[TMP2]], i32 0
+; CHECK-NEXT:    store <2 x i64> [[BROADCAST_SPLAT]], ptr [[TMP4]], align 8
+; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr inbounds i64, ptr [[TMP2]], i32 2
+; CHECK-NEXT:    store <2 x i64> [[BROADCAST_SPLAT2]], ptr [[TMP5]], align 8
+; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
+; CHECK-NEXT:    [[TMP6:%.*]] = icmp eq i64 [[INDEX_NEXT]], 1024
+; CHECK-NEXT:    br i1 [[TMP6]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP12:![0-9]+]]
+; CHECK:       middle.block:
+; CHECK-NEXT:    [[CMP_N:%.*]] = icmp eq i64 1024, 1024
+; CHECK-NEXT:    br i1 [[CMP_N]], label [[FOR_END:%.*]], label [[SCALAR_PH]]
+; CHECK:       scalar.ph:
+; CHECK-NEXT:    [[BC_RESUME_VAL:%.*]] = phi i64 [ 1024, [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[IV_NEXT:%.*]], [[FOR_BODY]] ]
+; CHECK-NEXT:    store i64 [[V]], ptr [[B]], align 8
+; CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i64, ptr [[A]], i64 [[IV]]
+; CHECK-NEXT:    store i64 [[V]], ptr [[ARRAYIDX]], align 8
+; CHECK-NEXT:    [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
+; CHECK-NEXT:    [[EXITCOND_NOT:%.*]] = icmp eq i64 [[IV_NEXT]], 1024
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_END]], label [[FOR_BODY]], !llvm.loop [[LOOP13:![0-9]+]]
+; CHECK:       for.end:
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %for.body
+
+for.body:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
+  store i64 %v, ptr %b, align 8
+  %arrayidx = getelementptr inbounds i64, ptr %a, i64 %iv
+  store i64 %v, ptr %arrayidx
+  %iv.next = add nuw nsw i64 %iv, 1
+  %exitcond.not = icmp eq i64 %iv.next, 1024
+  br i1 %exitcond.not, label %for.end, label %for.body
+
+for.end:
+  ret void
+}
+
+define void @uniform_store_unaligned(ptr noalias nocapture %a, ptr noalias nocapture %b, i64 %v, i64 %n) {
+; CHECK-LABEL: @uniform_store_unaligned(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
+; CHECK:       vector.ph:
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <2 x i64> poison, i64 [[V:%.*]], i32 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <2 x i64> [[BROADCAST_SPLATINSERT]], <2 x i64> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <2 x i64> poison, i64 [[V]], i32 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT2:%.*]] = shufflevector <2 x i64> [[BROADCAST_SPLATINSERT1]], <2 x i64> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = add i64 [[INDEX]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = add i64 [[INDEX]], 2
+; CHECK-NEXT:    store i64 [[V]], ptr [[B:%.*]], align 1
+; CHECK-NEXT:    store i64 [[V]], ptr [[B]], align 1
+; CHECK-NEXT:    store i64 [[V]], ptr [[B]], align 1
+; CHECK-NEXT:    store i64 [[V]], ptr [[B]], align 1
+; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr inbounds i64, ptr [[A:%.*]], i64 [[TMP0]]
+; CHECK-NEXT:    [[TMP3:%.*]] = getelementptr inbounds i64, ptr [[A]], i64 [[TMP1]]
+; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr inbounds i64, ptr [[TMP2]], i32 0
+; CHECK-NEXT:    store <2 x i64> [[BROADCAST_SPLAT]], ptr [[TMP4]], align 8
+; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr inbounds i64, ptr [[TMP2]], i32 2
+; CHECK-NEXT:    store <2 x i64> [[BROADCAST_SPLAT2]], ptr [[TMP5]], align 8
+; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
+; CHECK-NEXT:    [[TMP6:%.*]] = icmp eq i64 [[INDEX_NEXT]], 1024
+; CHECK-NEXT:    br i1 [[TMP6]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP14:![0-9]+]]
+; CHECK:       middle.block:
+; CHECK-NEXT:    [[CMP_N:%.*]] = icmp eq i64 1024, 1024
+; CHECK-NEXT:    br i1 [[CMP_N]], label [[FOR_END:%.*]], label [[SCALAR_PH]]
+; CHECK:       scalar.ph:
+; CHECK-NEXT:    [[BC_RESUME_VAL:%.*]] = phi i64 [ 1024, [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[IV_NEXT:%.*]], [[FOR_BODY]] ]
+; CHECK-NEXT:    store i64 [[V]], ptr [[B]], align 1
+; CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i64, ptr [[A]], i64 [[IV]]
+; CHECK-NEXT:    store i64 [[V]], ptr [[ARRAYIDX]], align 8
+; CHECK-NEXT:    [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
+; CHECK-NEXT:    [[EXITCOND_NOT:%.*]] = icmp eq i64 [[IV_NEXT]], 1024
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_END]], label [[FOR_BODY]], !llvm.loop [[LOOP15:![0-9]+]]
+; CHECK:       for.end:
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %for.body
+
+for.body:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
+  store i64 %v, ptr %b, align 1
+  %arrayidx = getelementptr inbounds i64, ptr %a, i64 %iv
+  store i64 %v, ptr %arrayidx
+  %iv.next = add nuw nsw i64 %iv, 1
+  %exitcond.not = icmp eq i64 %iv.next, 1024
+  br i1 %exitcond.not, label %for.end, label %for.body
+
+for.end:
+  ret void
+}
+
+define i64 @uniform_load(ptr noalias nocapture %a, ptr noalias nocapture %b, i64 %n) {
+; CHECK-LABEL: @uniform_load(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
+; CHECK:       vector.ph:
+; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = add i64 [[INDEX]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = add i64 [[INDEX]], 2
+; CHECK-NEXT:    [[TMP2:%.*]] = load i64, ptr [[B:%.*]], align 8
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <2 x i64> poison, i64 [[TMP2]], i32 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <2 x i64> [[BROADCAST_SPLATINSERT]], <2 x i64> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP3:%.*]] = load i64, ptr [[B]], align 8
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <2 x i64> poison, i64 [[TMP3]], i32 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT2:%.*]] = shufflevector <2 x i64> [[BROADCAST_SPLATINSERT1]], <2 x i64> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr inbounds i64, ptr [[A:%.*]], i64 [[TMP0]]
+; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr inbounds i64, ptr [[A]], i64 [[TMP1]]
+; CHECK-NEXT:    [[TMP6:%.*]] = getelementptr inbounds i64, ptr [[TMP4]], i32 0
+; CHECK-NEXT:    store <2 x i64> [[BROADCAST_SPLAT]], ptr [[TMP6]], align 8
+; CHECK-NEXT:    [[TMP7:%.*]] = getelementptr inbounds i64, ptr [[TMP4]], i32 2
+; CHECK-NEXT:    store <2 x i64> [[BROADCAST_SPLAT2]], ptr [[TMP7]], align 8
+; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
+; CHECK-NEXT:    [[TMP8:%.*]] = icmp eq i64 [[INDEX_NEXT]], 1024
+; CHECK-NEXT:    br i1 [[TMP8]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP16:![0-9]+]]
+; CHECK:       middle.block:
+; CHECK-NEXT:    [[CMP_N:%.*]] = icmp eq i64 1024, 1024
+; CHECK-NEXT:    br i1 [[CMP_N]], label [[FOR_END:%.*]], label [[SCALAR_PH]]
+; CHECK:       scalar.ph:
+; CHECK-NEXT:    [[BC_RESUME_VAL:%.*]] = phi i64 [ 1024, [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[IV_NEXT:%.*]], [[FOR_BODY]] ]
+; CHECK-NEXT:    [[V:%.*]] = load i64, ptr [[B]], align 8
+; CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i64, ptr [[A]], i64 [[IV]]
+; CHECK-NEXT:    store i64 [[V]], ptr [[ARRAYIDX]], align 8
+; CHECK-NEXT:    [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
+; CHECK-NEXT:    [[EXITCOND_NOT:%.*]] = icmp eq i64 [[IV_NEXT]], 1024
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_END]], label [[FOR_BODY]], !llvm.loop [[LOOP17:![0-9]+]]
+; CHECK:       for.end:
+; CHECK-NEXT:    [[V_LCSSA:%.*]] = phi i64 [ [[V]], [[FOR_BODY]] ], [ [[TMP3]], [[MIDDLE_BLOCK]] ]
+; CHECK-NEXT:    ret i64 [[V_LCSSA]]
+;
+entry:
+  br label %for.body
+
+for.body:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
+  %v = load i64, ptr %b, align 8
+  %arrayidx = getelementptr inbounds i64, ptr %a, i64 %iv
+  store i64 %v, ptr %arrayidx
+  %iv.next = add nuw nsw i64 %iv, 1
+  %exitcond.not = icmp eq i64 %iv.next, 1024
+  br i1 %exitcond.not, label %for.end, label %for.body
+
+for.end:
+  ret i64 %v
+}
+
+define i64 @uniform_load_unaligned(ptr noalias nocapture %a, ptr noalias nocapture %b, i64 %n) {
+; CHECK-LABEL: @uniform_load_unaligned(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
+; CHECK:       vector.ph:
+; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = add i64 [[INDEX]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = add i64 [[INDEX]], 2
+; CHECK-NEXT:    [[TMP2:%.*]] = load i64, ptr [[B:%.*]], align 1
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <2 x i64> poison, i64 [[TMP2]], i32 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <2 x i64> [[BROADCAST_SPLATINSERT]], <2 x i64> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP3:%.*]] = load i64, ptr [[B]], align 1
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <2 x i64> poison, i64 [[TMP3]], i32 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT2:%.*]] = shufflevector <2 x i64> [[BROADCAST_SPLATINSERT1]], <2 x i64> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr inbounds i64, ptr [[A:%.*]], i64 [[TMP0]]
+; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr inbounds i64, ptr [[A]], i64 [[TMP1]]
+; CHECK-NEXT:    [[TMP6:%.*]] = getelementptr inbounds i64, ptr [[TMP4]], i32 0
+; CHECK-NEXT:    store <2 x i64> [[BROADCAST_SPLAT]], ptr [[TMP6]], align 8
+; CHECK-NEXT:    [[TMP7:%.*]] = getelementptr inbounds i64, ptr [[TMP4]], i32 2
+; CHECK-NEXT:    store <2 x i64> [[BROADCAST_SPLAT2]], ptr [[TMP7]], align 8
+; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
+; CHECK-NEXT:    [[TMP8:%.*]] = icmp eq i64 [[INDEX_NEXT]], 1024
+; CHECK-NEXT:    br i1 [[TMP8]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP18:![0-9]+]]
+; CHECK:       middle.block:
+; CHECK-NEXT:    [[CMP_N:%.*]] = icmp eq i64 1024, 1024
+; CHECK-NEXT:    br i1 [[CMP_N]], label [[FOR_END:%.*]], label [[SCALAR_PH]]
+; CHECK:       scalar.ph:
+; CHECK-NEXT:    [[BC_RESUME_VAL:%.*]] = phi i64 [ 1024, [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[IV_NEXT:%.*]], [[FOR_BODY]] ]
+; CHECK-NEXT:    [[V:%.*]] = load i64, ptr [[B]], align 1
+; CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i64, ptr [[A]], i64 [[IV]]
+; CHECK-NEXT:    store i64 [[V]], ptr [[ARRAYIDX]], align 8
+; CHECK-NEXT:    [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
+; CHECK-NEXT:    [[EXITCOND_NOT:%.*]] = icmp eq i64 [[IV_NEXT]], 1024
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_END]], label [[FOR_BODY]], !llvm.loop [[LOOP19:![0-9]+]]
+; CHECK:       for.end:
+; CHECK-NEXT:    [[V_LCSSA:%.*]] = phi i64 [ [[V]], [[FOR_BODY]] ], [ [[TMP3]], [[MIDDLE_BLOCK]] ]
+; CHECK-NEXT:    ret i64 [[V_LCSSA]]
+;
+entry:
+  br label %for.body
+
+for.body:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
+  %v = load i64, ptr %b, align 1
+  %arrayidx = getelementptr inbounds i64, ptr %a, i64 %iv
+  store i64 %v, ptr %arrayidx
+  %iv.next = add nuw nsw i64 %iv, 1
+  %exitcond.not = icmp eq i64 %iv.next, 1024
+  br i1 %exitcond.not, label %for.end, label %for.body
+
+for.end:
+  ret i64 %v
+}


        


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