[llvm] 3c03635 - [SVE][LoopVectorize] Add support for scalable vectorization of loops with vector reverse

Caroline Concatto via llvm-commits llvm-commits at lists.llvm.org
Tue Mar 16 02:19:04 PDT 2021


Author: Caroline Concatto
Date: 2021-03-16T07:51:59Z
New Revision: 3c03635d530066028aa3e041bc9e68743281e56b

URL: https://github.com/llvm/llvm-project/commit/3c03635d530066028aa3e041bc9e68743281e56b
DIFF: https://github.com/llvm/llvm-project/commit/3c03635d530066028aa3e041bc9e68743281e56b.diff

LOG: [SVE][LoopVectorize] Add support for scalable vectorization of loops with vector reverse

This patch adds support for reverse loop vectorization.
It is possible to vectorize the following loop:
```
  for (int i = n-1; i >= 0; --i)
    a[i] = b[i] + 1.0;
```
with fixed or scalable vector.
The loop-vectorizer will use 'reverse' on the loads/stores to make
sure the lanes themselves are also handled in the right order.
This patch adds support for scalable vector on IRBuilder interface to
create a reverse vector. The IR function
CreateVectorReverse lowers to experimental.vector.reverse for scalable vector
and keedp the original behavior for fixed vector using shuffle reverse.

Differential Revision: https://reviews.llvm.org/D95363

Added: 
    llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse-mask4.ll
    llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse.ll
    llvm/test/Transforms/LoopVectorize/AArch64/vector-reverse-mask4.ll
    llvm/test/Transforms/LoopVectorize/AArch64/vector-reverse.ll

Modified: 
    llvm/include/llvm/IR/IRBuilder.h
    llvm/lib/IR/IRBuilder.cpp
    llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/IR/IRBuilder.h b/llvm/include/llvm/IR/IRBuilder.h
index 477d4815bc9d..f2da98a98b70 100644
--- a/llvm/include/llvm/IR/IRBuilder.h
+++ b/llvm/include/llvm/IR/IRBuilder.h
@@ -2504,6 +2504,9 @@ class IRBuilderBase {
   /// address space before call and casted back to Ptr type after call.
   Value *CreateStripInvariantGroup(Value *Ptr);
 
+  /// Return a vector value that contains the vector V reversed
+  Value *CreateVectorReverse(Value *V, const Twine &Name = "");
+
   /// Return a vector value that contains \arg V broadcasted to \p
   /// NumElts elements.
   Value *CreateVectorSplat(unsigned NumElts, Value *V, const Twine &Name = "");

diff  --git a/llvm/lib/IR/IRBuilder.cpp b/llvm/lib/IR/IRBuilder.cpp
index 81fa2098c485..d4292b3cfc1b 100644
--- a/llvm/lib/IR/IRBuilder.cpp
+++ b/llvm/lib/IR/IRBuilder.cpp
@@ -992,6 +992,22 @@ Value *IRBuilderBase::CreateStripInvariantGroup(Value *Ptr) {
   return Fn;
 }
 
+Value *IRBuilderBase::CreateVectorReverse(Value *V, const Twine &Name) {
+  auto *Ty = cast<VectorType>(V->getType());
+  if (isa<ScalableVectorType>(Ty)) {
+    Module *M = BB->getParent()->getParent();
+    Function *F = Intrinsic::getDeclaration(
+        M, Intrinsic::experimental_vector_reverse, Ty);
+    return Insert(CallInst::Create(F, V), Name);
+  }
+  // Keep the original behaviour for fixed vector
+  SmallVector<int, 8> ShuffleMask;
+  int NumElts = Ty->getElementCount().getKnownMinValue();
+  for (int i = 0; i < NumElts; ++i)
+    ShuffleMask.push_back(NumElts - i - 1);
+  return CreateShuffleVector(V, ShuffleMask, Name);
+}
+
 Value *IRBuilderBase::CreateVectorSplat(unsigned NumElts, Value *V,
                                         const Twine &Name) {
   auto EC = ElementCount::getFixed(NumElts);

diff  --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 1fb99e9e7857..c92b00078c7e 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -2568,12 +2568,7 @@ void InnerLoopVectorizer::packScalarIntoVectorValue(VPValue *Def,
 
 Value *InnerLoopVectorizer::reverseVector(Value *Vec) {
   assert(Vec->getType()->isVectorTy() && "Invalid type");
-  assert(!VF.isScalable() && "Cannot reverse scalable vectors");
-  SmallVector<int, 8> ShuffleMask;
-  for (unsigned i = 0; i < VF.getKnownMinValue(); ++i)
-    ShuffleMask.push_back(VF.getKnownMinValue() - i - 1);
-
-  return Builder.CreateShuffleVector(Vec, ShuffleMask, "reverse");
+  return Builder.CreateVectorReverse(Vec, "reverse");
 }
 
 // Return whether we allow using masked interleave-groups (for dealing with
@@ -2854,18 +2849,21 @@ void InnerLoopVectorizer::vectorizeMemoryInstruction(
     bool InBounds = false;
     if (auto *gep = dyn_cast<GetElementPtrInst>(Ptr->stripPointerCasts()))
       InBounds = gep->isInBounds();
-
     if (Reverse) {
-      assert(!VF.isScalable() &&
-             "Reversing vectors is not yet supported for scalable vectors.");
-
       // If the address is consecutive but reversed, then the
       // wide store needs to start at the last vector element.
-      PartPtr = cast<GetElementPtrInst>(Builder.CreateGEP(
-          ScalarDataTy, Ptr, Builder.getInt32(-Part * VF.getKnownMinValue())));
+      // RunTimeVF =  VScale * VF.getKnownMinValue()
+      // For fixed-width VScale is 1, then RunTimeVF = VF.getKnownMinValue()
+      Value *RunTimeVF = getRuntimeVF(Builder, Builder.getInt32Ty(), VF);
+      // NumElt = -Part * RunTimeVF
+      Value *NumElt = Builder.CreateMul(Builder.getInt32(-Part), RunTimeVF);
+      // LastLane = 1 - RunTimeVF
+      Value *LastLane = Builder.CreateSub(Builder.getInt32(1), RunTimeVF);
+      PartPtr =
+          cast<GetElementPtrInst>(Builder.CreateGEP(ScalarDataTy, Ptr, NumElt));
       PartPtr->setIsInBounds(InBounds);
-      PartPtr = cast<GetElementPtrInst>(Builder.CreateGEP(
-          ScalarDataTy, PartPtr, Builder.getInt32(1 - VF.getKnownMinValue())));
+      PartPtr = cast<GetElementPtrInst>(
+          Builder.CreateGEP(ScalarDataTy, PartPtr, LastLane));
       PartPtr->setIsInBounds(InBounds);
       if (isMaskRequired) // Reverse of a null all-one mask is a null mask.
         BlockInMaskParts[Part] = reverseVector(BlockInMaskParts[Part]);

diff  --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse-mask4.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse-mask4.ll
new file mode 100644
index 000000000000..d803f6b75ed9
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse-mask4.ll
@@ -0,0 +1,68 @@
+; This is the loop in c++ being vectorize in this file with 
+; experimental.vector.reverse
+
+;#pragma clang loop vectorize_width(4, scalable)
+;  for (long int i = N - 1; i >= 0; i--)
+;  {
+;    if (cond[i])
+;      a[i] += 1;
+;  }
+
+; The test checks if the mask is being correctly created, reverted and used
+
+; RUN: opt -loop-vectorize -dce -instcombine -mtriple aarch64-linux-gnu -S < %s 2>%t | FileCheck %s
+
+; RUN: FileCheck --check-prefix=WARN --allow-empty %s <%t
+
+; If this check fails please read test/CodeGen/AArch64/README for instructions on how to resolve it.
+; WARN-NOT: warning
+
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-unknown-linux-gnu"
+
+define void @vector_reverse_mask_nxv4i1(double* %a, double* %cond, i64 %N) #0 {
+; CHECK-LABEL: vector.body:
+; CHECK: %[[REVERSE6:.*]] = call <vscale x 4 x i1> @llvm.experimental.vector.reverse.nxv4i1(<vscale x 4 x i1> %{{.*}})
+; CHECK: %[[WIDEMSKLOAD:.*]] = call <vscale x 4 x double> @llvm.masked.load.nxv4f64.p0nxv4f64(<vscale x 4 x double>* nonnull %{{.*}}, i32 8, <vscale x 4 x i1> %[[REVERSE6]], <vscale x 4 x double> poison)
+; CHECK-NEXT: %[[REVERSE7:.*]] = call <vscale x 4 x double> @llvm.experimental.vector.reverse.nxv4f64(<vscale x 4 x double> %[[WIDEMSKLOAD]])
+; CHECK-NEXT: %[[FADD:.*]] = fadd <vscale x 4 x double> %[[REVERSE7]]
+; CHECK-NEXT: %[[REVERSE8:.*]] = call <vscale x 4 x double> @llvm.experimental.vector.reverse.nxv4f64(<vscale x 4 x double> %[[FADD]])
+; CHECK:  %[[REVERSE9:.*]] = call <vscale x 4 x i1> @llvm.experimental.vector.reverse.nxv4i1(<vscale x 4 x i1> %{{.*}})
+; CHECK: call void @llvm.masked.store.nxv4f64.p0nxv4f64(<vscale x 4 x double> %[[REVERSE8]], <vscale x 4 x double>* %{{.*}}, i32 8, <vscale x 4 x i1> %[[REVERSE9]]
+
+entry:
+  %cmp7 = icmp sgt i64 %N, 0
+  br i1 %cmp7, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.cond.cleanup, %entry
+  ret void
+
+for.body:                                         ; preds = %for.body, %entry
+  %i.08.in = phi i64 [ %i.08, %for.inc ], [ %N, %entry ]
+  %i.08 = add nsw i64 %i.08.in, -1
+  %arrayidx = getelementptr inbounds double, double* %cond, i64 %i.08
+  %0 = load double, double* %arrayidx, align 8
+  %tobool = fcmp une double %0, 0.000000e+00
+  br i1 %tobool, label %if.then, label %for.inc
+
+if.then:                                          ; preds = %for.body
+  %arrayidx1 = getelementptr inbounds double, double* %a, i64 %i.08
+  %1 = load double, double* %arrayidx1, align 8
+  %add = fadd double %1, 1.000000e+00
+  store double %add, double* %arrayidx1, align 8
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %cmp = icmp sgt i64 %i.08.in, 1
+  br i1 %cmp, label %for.body, label %for.cond.cleanup, !llvm.loop !0
+}
+
+attributes #0 = {"target-cpu"="generic" "target-features"="+neon,+sve"}
+
+
+!0 = distinct !{!0, !1, !2, !3, !4}
+!1 = !{!"llvm.loop.mustprogress"}
+!2 = !{!"llvm.loop.vectorize.width", i32 4}
+!3 = !{!"llvm.loop.vectorize.scalable.enable", i1 true}
+!4 = !{!"llvm.loop.vectorize.enable", i1 true}

diff  --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse.ll
new file mode 100644
index 000000000000..aef5efe030f5
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-vector-reverse.ll
@@ -0,0 +1,108 @@
+; This is the loop in c++ being vectorize in this file with
+;experimental.vector.reverse
+;  #pragma clang loop vectorize_width(8, scalable)
+;  for (int i = N-1; i >= 0; --i)
+;    a[i] = b[i] + 1.0;
+
+; RUN: opt -loop-vectorize -dce -instcombine -mtriple aarch64-linux-gnu -S < %s 2>%t | FileCheck %s
+
+; RUN: FileCheck --check-prefix=WARN --allow-empty %s <%t
+
+; If this check fails please read test/CodeGen/AArch64/README for instructions on how to resolve it.
+; WARN-NOT: warning
+
+define void @vector_reverse_f64(i64 %N, double* %a, double* %b) #0{
+; CHECK-LABEL: @vector_reverse_f64
+; CHECK-LABEL: vector.body:
+; CHECK: %[[ADD:.*]] = add i64 %{{.*}}, %N
+; CHECK-NEXT: %[[GEP:.*]] = getelementptr inbounds double, double* %b, i64 %[[ADD]]
+; CHECK-NEXT: %[[VSCALE:.*]] = call i32 @llvm.vscale.i32()
+; CHECK-NEXT: %[[MUL:.*]] = mul i32 %[[VSCALE]], -8
+; CHECK-NEXT: %[[OR:.*]] = or i32 %[[MUL]], 1
+; CHECK-NEXT: %[[SEXT:.*]] = sext i32 %[[OR]] to i64
+; CHECK-NEXT: %[[GEP1:.*]] = getelementptr inbounds double, double* %[[GEP]], i64 %[[SEXT]]
+; CHECK-NEXT: %[[CAST:.*]] = bitcast double* %[[GEP1]] to <vscale x 8 x double>*
+; CHECK-NEXT: %[[WIDE:.*]] = load <vscale x 8 x double>, <vscale x 8 x double>* %[[CAST]], align 8
+; CHECK-NEXT: %[[REVERSE:.*]] = call <vscale x 8 x double> @llvm.experimental.vector.reverse.nxv8f64(<vscale x 8 x double> %[[WIDE]])
+; CHECK-NEXT: %[[FADD:.*]] = fadd <vscale x 8 x double> %[[REVERSE]], shufflevector
+; CHECK-NEXT: %[[GEP2:.*]] = getelementptr inbounds double, double* %a, i64 %[[ADD]]
+; CHECK-NEXT: %[[REVERSE6:.*]] = call <vscale x 8 x double> @llvm.experimental.vector.reverse.nxv8f64(<vscale x 8 x double> %[[FADD]])
+; CHECK-NEXT: %[[VSCALE1:.*]] = call i32 @llvm.vscale.i32()
+; CHECK-NEXT: %[[MUL1:.*]] = mul i32 %[[VSCALE1]], -8
+; CHECK-NEXT: %[[OR1:.*]] = or i32 %[[MUL1]], 1
+; CHECK-NEXT: %[[SEXT1:.*]] = sext i32 %[[OR1]] to i64
+; CHECK-NEXT: %[[GEP3:.*]] = getelementptr inbounds double, double* %[[GEP2]], i64 %[[SEXT1]]
+; CHECK-NEXT: %[[CAST1:.*]] = bitcast double* %[[GEP3]] to <vscale x 8 x double>*
+; CHECK-NEXT: store <vscale x 8 x double> %[[REVERSE6]], <vscale x 8 x double>* %[[CAST1]], align 8
+
+entry:
+  %cmp7 = icmp sgt i64 %N, 0
+  br i1 %cmp7, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.body
+  ret void
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.08.in = phi i64 [ %i.08, %for.body ], [ %N, %entry ]
+  %i.08 = add nsw i64 %i.08.in, -1
+  %arrayidx = getelementptr inbounds double, double* %b, i64 %i.08
+  %0 = load double, double* %arrayidx, align 8
+  %add = fadd double %0, 1.000000e+00
+  %arrayidx1 = getelementptr inbounds double, double* %a, i64 %i.08
+  store double %add, double* %arrayidx1, align 8
+  %cmp = icmp sgt i64 %i.08.in, 1
+  br i1 %cmp, label %for.body, label %for.cond.cleanup, !llvm.loop !0
+}
+
+
+define void @vector_reverse_i64(i64 %N, i64* %a, i64* %b) #0 {
+; CHECK-LABEL: vector_reverse_i64
+; CHECK-LABEL: vector.body:
+; CHECK: %[[ADD:.*]] = add i64 %{{.*}}, %N
+; CHECK-NEXT: %[[GEP:.*]] = getelementptr inbounds i64, i64* %b, i64 %[[ADD]]
+; CHECK-NEXT: %[[VSCALE:.*]] = call i32 @llvm.vscale.i32()
+; CHECK-NEXT: %[[MUL:.*]] = mul i32 %[[VSCALE]], -8
+; CHECK-NEXT: %[[OR:.*]] = or i32 %[[MUL]], 1
+; CHECK-NEXT: %[[SEXT:.*]] = sext i32 %[[OR]] to i64
+; CHECK-NEXT: %[[GEP1:.*]] = getelementptr inbounds i64, i64* %[[GEP]], i64 %[[SEXT]]
+; CHECK-NEXT: %[[CAST:.*]] = bitcast i64* %[[GEP1]] to <vscale x 8 x i64>*
+; CHECK-NEXT: %[[WIDE:.*]] = load <vscale x 8 x i64>, <vscale x 8 x i64>* %[[CAST]], align 8
+; CHECK-NEXT: %[[REVERSE:.*]] = call <vscale x 8 x i64> @llvm.experimental.vector.reverse.nxv8i64(<vscale x 8 x i64> %[[WIDE]])
+; CHECK-NEXT: %[[ADD1:.*]] = add <vscale x 8 x i64> %[[REVERSE]]
+; CHECK-NEXT: %[[GEP2:.*]] = getelementptr inbounds i64, i64* %a, i64 %[[ADD]]
+; CHECK-NEXT: %[[REVERSE6]] = call <vscale x 8 x i64> @llvm.experimental.vector.reverse.nxv8i64(<vscale x 8 x i64> %[[ADD1]])
+; CHECK-NEXT: %[[VSCALE:.*]] = call i32 @llvm.vscale.i32()
+; CHECK-NEXT: %[[MUL1:.*]] = mul i32 %[[VSCALE]], -8
+; CHECK-NEXT: %[[OR1:.*]] = or i32 %[[MUL1]], 1
+; CHECK-NEXT: %[[SEXT1:.*]] = sext i32 %[[OR1]] to i64
+; CHECK-NEXT: %[[GEP3:.*]] = getelementptr inbounds i64, i64* %[[GEP2]], i64 %[[SEXT1]]
+; CHECK-NEXT: %[[CAST1:.*]] = bitcast i64* %[[GEP3]] to <vscale x 8 x i64>*
+; CHECK-NEXT:  store <vscale x 8 x i64> %[[REVERSE6]], <vscale x 8 x i64>* %[[CAST1]], align 8
+
+entry:
+  %cmp8 = icmp sgt i64 %N, 0
+  br i1 %cmp8, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.body
+  ret void
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.09.in = phi i64 [ %i.09, %for.body ], [ %N, %entry ]
+  %i.09 = add nsw i64 %i.09.in, -1
+  %arrayidx = getelementptr inbounds i64, i64* %b, i64 %i.09
+  %0 = load i64, i64* %arrayidx, align 8
+  %add = add i64 %0, 1
+  %arrayidx2 = getelementptr inbounds i64, i64* %a, i64 %i.09
+  store i64 %add, i64* %arrayidx2, align 8
+  %cmp = icmp sgt i64 %i.09.in, 1
+  br i1 %cmp, label %for.body, label %for.cond.cleanup, !llvm.loop !0
+}
+
+attributes #0 = { "target-cpu"="generic" "target-features"="+neon,+sve" }
+
+!0 = distinct !{!0, !1, !2, !3, !4}
+!1 = !{!"llvm.loop.mustprogress"}
+!2 = !{!"llvm.loop.vectorize.width", i32 8}
+!3 = !{!"llvm.loop.vectorize.scalable.enable", i1 true}
+!4 = !{!"llvm.loop.vectorize.enable", i1 true}
+

diff  --git a/llvm/test/Transforms/LoopVectorize/AArch64/vector-reverse-mask4.ll b/llvm/test/Transforms/LoopVectorize/AArch64/vector-reverse-mask4.ll
new file mode 100644
index 000000000000..22de7c1e1ca8
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/vector-reverse-mask4.ll
@@ -0,0 +1,65 @@
+; This is the loop in c++ being vectorize in this file with 
+; shuffle reverse
+
+;#pragma clang loop vectorize_width(4, fixed)
+;  for (long int i = N - 1; i >= 0; i--)
+;  {
+;    if (cond[i])
+;      a[i] += 1;
+;  }
+
+; The test checks if the mask is being correctly created, reverted  and used
+
+; RUN: opt -loop-vectorize -dce -instcombine -mtriple aarch64-linux-gnu -S < %s 2>%t | FileCheck %s
+
+; RUN: FileCheck --check-prefix=WARN --allow-empty %s <%t
+
+; If this check fails please read test/CodeGen/AArch64/README for instructions on how to resolve it.
+; WARN-NOT: warning
+
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-unknown-linux-gnu"
+
+define void @vector_reverse_mask_v4i1(double* %a, double* %cond, i64 %N) #0 {
+; CHECK-LABEL: vector.body:
+; CHECK: %[[REVERSE6:.*]] = shufflevector <4 x i1> %{{.*}}, <4 x i1> poison, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
+; CHECK: %[[WIDEMSKLOAD:.*]] = call <4 x double> @llvm.masked.load.v4f64.p0v4f64(<4 x double>* nonnull %{{.*}}, i32 8, <4 x i1> %[[REVERSE6]], <4 x double> poison)
+; CHECK-NEXT: %[[FADD:.*]] = fadd <4 x double> %[[WIDEMSKLOAD]]
+; CHECK: call void @llvm.masked.store.v4f64.p0v4f64(<4 x double> %[[FADD]], <4 x double>* %{{.*}}, i32 8, <4 x i1> %[[REVERSE6]])
+
+entry:
+  %cmp7 = icmp sgt i64 %N, 0
+  br i1 %cmp7, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.cond.cleanup, %entry
+  ret void
+
+for.body:                                         ; preds = %for.body, %entry
+  %i.08.in = phi i64 [ %i.08, %for.inc ], [ %N, %entry ]
+  %i.08 = add nsw i64 %i.08.in, -1
+  %arrayidx = getelementptr inbounds double, double* %cond, i64 %i.08
+  %0 = load double, double* %arrayidx, align 8
+  %tobool = fcmp une double %0, 0.000000e+00
+  br i1 %tobool, label %if.then, label %for.inc
+
+if.then:                                          ; preds = %for.body
+  %arrayidx1 = getelementptr inbounds double, double* %a, i64 %i.08
+  %1 = load double, double* %arrayidx1, align 8
+  %add = fadd double %1, 1.000000e+00
+  store double %add, double* %arrayidx1, align 8
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %cmp = icmp sgt i64 %i.08.in, 1
+  br i1 %cmp, label %for.body, label %for.cond.cleanup, !llvm.loop !0
+}
+
+attributes #0 = {"target-cpu"="generic" "target-features"="+neon,+sve"}
+
+
+!0 = distinct !{!0, !1, !2, !3, !4}
+!1 = !{!"llvm.loop.mustprogress"}
+!2 = !{!"llvm.loop.vectorize.width", i32 4}
+!3 = !{!"llvm.loop.vectorize.scalable.enable", i1 false}
+!4 = !{!"llvm.loop.vectorize.enable", i1 true}

diff  --git a/llvm/test/Transforms/LoopVectorize/AArch64/vector-reverse.ll b/llvm/test/Transforms/LoopVectorize/AArch64/vector-reverse.ll
new file mode 100644
index 000000000000..ae3aad1e75a8
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/vector-reverse.ll
@@ -0,0 +1,91 @@
+; Test VLA for reverse with fixed size vector
+; This is the loop in c++ being vectorize in this file with
+; shuffle reverse
+;  #pragma clang loop vectorize_width(8, fixed)
+;  for (int i = N-1; i >= 0; --i)
+;    a[i] = b[i] + 1.0;
+
+; RUN: opt -loop-vectorize -dce  -mtriple aarch64-linux-gnu -S < %s 2>%t | FileCheck %s
+
+; RUN: FileCheck --check-prefix=WARN --allow-empty %s <%t
+
+; If this check fails please read test/CodeGen/AArch64/README for instructions on how to resolve it.$
+; WARN-NOT: warning
+
+define void @vector_reverse_f64(i64 %N, double* %a, double* %b) #0 {
+; CHECK-LABEL: vector_reverse_f64
+; CHECK-LABEL: vector.body
+; CHECK: %[[GEP:.*]] = getelementptr inbounds double, double* %{{.*}}, i32 0
+; CHECK-NEXT: %[[GEP1:.*]] = getelementptr inbounds double, double* %[[GEP]], i32 -7
+; CHECK-NEXT: %[[CAST:.*]] = bitcast double* %[[GEP1]] to <8 x double>*
+; CHECK-NEXT: %[[WIDE:.*]] = load <8 x double>, <8 x double>* %[[CAST]], align 8
+; CHECK-NEXT: %[[REVERSE:.*]] = shufflevector <8 x double> %[[WIDE]], <8 x double> poison, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT: %[[FADD:.*]] = fadd <8 x double> %[[REVERSE]]
+; CHECK-NEXT: %[[GEP2:.*]] = getelementptr inbounds double, double* {{.*}}, i64 {{.*}}
+; CHECK-NEXT: %[[REVERSE6:.*]] = shufflevector <8 x double> %[[FADD]], <8 x double> poison, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT: %[[GEP3:.*]] = getelementptr inbounds double, double* %[[GEP2]], i32 0
+; CHECK-NEXT: %[[GEP4:.*]] = getelementptr inbounds double, double* %[[GEP3]], i32 -7
+; CHECK-NEXT: %[[CAST:.*]] = bitcast double* %[[GEP4]] to <8 x double>*
+; CHECK-NEXT:  store <8 x double> %[[REVERSE6]], <8 x double>* %[[CAST]], align 8
+
+entry:
+  %cmp7 = icmp sgt i64 %N, 0
+  br i1 %cmp7, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.cond.cleanup, %entry
+  ret void
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.08.in = phi i64 [ %i.08, %for.body ], [ %N, %entry ]
+  %i.08 = add nsw i64 %i.08.in, -1
+  %arrayidx = getelementptr inbounds double, double* %b, i64 %i.08
+  %0 = load double, double* %arrayidx, align 8
+  %add = fadd double %0, 1.000000e+00
+  %arrayidx1 = getelementptr inbounds double, double* %a, i64 %i.08
+  store double %add, double* %arrayidx1, align 8
+  %cmp = icmp sgt i64 %i.08.in, 1
+  br i1 %cmp, label %for.body, label %for.cond.cleanup, !llvm.loop !0
+}
+
+define void @vector_reverse_i64(i64 %N, i64* %a, i64* %b) #0 {
+; CHECK-LABEL: vector_reverse_i64
+; CHECK-LABEL: vector.body
+; CHECK: %[[GEP:.*]] = getelementptr inbounds i64, i64* %{{.*}}, i32 0
+; CHECK-NEXT: %[[GEP1:.*]] = getelementptr inbounds i64, i64* %[[GEP]], i32 -7
+; CHECK-NEXT: %[[CAST:.*]] = bitcast i64* %[[GEP1]] to <8 x i64>*
+; CHECK-NEXT: %[[WIDE:.*]] = load <8 x i64>, <8 x i64>* %[[CAST]], align 8
+; CHECK-NEXT: %[[REVERSE:.*]] = shufflevector <8 x i64> %[[WIDE]], <8 x i64> poison, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT: %[[FADD:.*]] = add <8 x i64> %[[REVERSE]]
+; CHECK-NEXT: %[[GEP2:.*]] = getelementptr inbounds i64, i64* {{.*}}, i64 {{.*}}
+; CHECK-NEXT: %[[REVERSE6:.*]] = shufflevector <8 x i64> %[[FADD]], <8 x i64> poison, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT: %[[GEP3:.*]] = getelementptr inbounds i64, i64* %[[GEP2]], i32 0
+; CHECK-NEXT: %[[GEP4:.*]] = getelementptr inbounds i64, i64* %[[GEP3]], i32 -7
+; CHECK-NEXT: %[[CAST1:.*]] = bitcast i64* %[[GEP4]] to <8 x i64>*
+; CHECK-NEXT:  store <8 x i64> %[[REVERSE6]], <8 x i64>* %[[CAST1]], align 8
+
+entry:
+  %cmp8 = icmp sgt i64 %N, 0
+  br i1 %cmp8, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.cond.cleanup, %entry
+  ret void
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.09.in = phi i64 [ %i.09, %for.body ], [ %N, %entry ]
+  %i.09 = add nsw i64 %i.09.in, -1
+  %arrayidx = getelementptr inbounds i64, i64* %b, i64 %i.09
+  %0 = load i64, i64* %arrayidx, align 8
+  %add = add i64 %0, 1
+  %arrayidx2 = getelementptr inbounds i64, i64* %a, i64 %i.09
+  store i64 %add, i64* %arrayidx2, align 8
+  %cmp = icmp sgt i64 %i.09.in, 1
+  br i1 %cmp, label %for.body, label %for.cond.cleanup, !llvm.loop !0
+}
+
+attributes #0 = { "target-cpu"="generic" "target-features"="+neon,+sve" }
+
+!0 = distinct !{!0, !1, !2, !3, !4}
+!1 = !{!"llvm.loop.mustprogress"}
+!2 = !{!"llvm.loop.vectorize.width", i32 8}
+!3 = !{!"llvm.loop.vectorize.scalable.enable", i1 false}
+!4 = !{!"llvm.loop.vectorize.enable", i1 true}


        


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