Second attempt at r285517.

llvm-svn: 285568

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -5734,7 +5734,15 @@ void InterleavedAccessInfo::collectConstStrideAccesses(
         continue;
 
       Value *Ptr = getPointerOperand(&I);
-      int64_t Stride = getPtrStride(PSE, Ptr, TheLoop, Strides);
+      // We don't check wrapping here because we don't know yet if Ptr will be 
+      // part of a full group or a group with gaps. Checking wrapping for all 
+      // pointers (even those that end up in groups with no gaps) will be overly
+      // conservative. For full groups, wrapping should be ok since if we would 
+      // wrap around the address space we would do a memory access at nullptr
+      // even without the transformation. The wrapping checks are therefore
+      // deferred until after we've formed the interleaved groups.
+      int64_t Stride = getPtrStride(PSE, Ptr, TheLoop, Strides,
+                                    /*Assume=*/true, /*ShouldCheckWrap=*/false);
 
       const SCEV *Scev = replaceSymbolicStrideSCEV(PSE, Strides, Ptr);
       PointerType *PtrTy = dyn_cast<PointerType>(Ptr->getType());
@@ -5938,20 +5946,66 @@ void InterleavedAccessInfo::analyzeInterleaving(
     if (Group->getNumMembers() != Group->getFactor())
       releaseGroup(Group);
 
-  // If there is a non-reversed interleaved load group with gaps, we will need
+  // Remove interleaved groups with gaps (currently only loads) whose memory 
-  // to execute at least one scalar epilogue iteration. This will ensure that
+  // accesses may wrap around. We have to revisit the getPtrStride analysis, 
-  // we don't speculatively access memory out-of-bounds. Note that we only need
+  // this time with ShouldCheckWrap=true, since collectConstStrideAccesses does 
-  // to look for a member at index factor - 1, since every group must have a
+  // not check wrapping (see documentation there).
-  // member at index zero.
+  // FORNOW we use Assume=false; 
-  for (InterleaveGroup *Group : LoadGroups)
+  // TODO: Change to Assume=true but making sure we don't exceed the threshold 
-    if (!Group->getMember(Group->getFactor() - 1)) {
+  // of runtime SCEV assumptions checks (thereby potentially failing to
-      if (Group->isReverse()) {
+  // vectorize altogether). 
+  // Additional optional optimizations:
+  // TODO: If we are peeling the loop and we know that the first pointer doesn't 
+  // wrap then we can deduce that all pointers in the group don't wrap.
+  // This means that we can forcefully peel the loop in order to only have to 
+  // check the first pointer for no-wrap. When we'll change to use Assume=true 
+  // we'll only need at most one runtime check per interleaved group.
+  //
+  for (InterleaveGroup *Group : LoadGroups) {
+
+    // Case 1: A full group. Can Skip the checks; For full groups, if the wide
+    // load would wrap around the address space we would do a memory access at 
+    // nullptr even without the transformation. 
+    if (Group->getNumMembers() == Group->getFactor()) 
+      continue;
+
+    // Case 2: If first and last members of the group don't wrap this implies 
+    // that all the pointers in the group don't wrap.
+    // So we check only group member 0 (which is always guaranteed to exist),
+    // and group member Factor - 1; If the latter doesn't exist we rely on 
+    // peeling (if it is a non-reveresed accsess -- see Case 3).
+    Value *FirstMemberPtr = getPointerOperand(Group->getMember(0));
+    if (!getPtrStride(PSE, FirstMemberPtr, TheLoop, Strides, /*Assume=*/false, 
+                      /*ShouldCheckWrap=*/true)) {
+      DEBUG(dbgs() << "LV: Invalidate candidate interleaved group due to "
+                      "first group member potentially pointer-wrapping.\n");
+      releaseGroup(Group);
+      continue;
+    }
+    Instruction *LastMember = Group->getMember(Group->getFactor() - 1);
+    if (LastMember) {
+      Value *LastMemberPtr = getPointerOperand(LastMember);
+      if (!getPtrStride(PSE, LastMemberPtr, TheLoop, Strides, /*Assume=*/false, 
+                        /*ShouldCheckWrap=*/true)) {
+        DEBUG(dbgs() << "LV: Invalidate candidate interleaved group due to "
+                        "last group member potentially pointer-wrapping.\n");
         releaseGroup(Group);
-      } else {
-        DEBUG(dbgs() << "LV: Interleaved group requires epilogue iteration.\n");
-        RequiresScalarEpilogue = true;
       }
     }
+    else {
+      // Case 3: A non-reversed interleaved load group with gaps: We need
+      // to execute at least one scalar epilogue iteration. This will ensure 
+      // we don't speculatively access memory out-of-bounds. We only need
+      // to look for a member at index factor - 1, since every group must have 
+      // a member at index zero.
+      if (Group->isReverse()) {
+        releaseGroup(Group);
+        continue;
+      }
+      DEBUG(dbgs() << "LV: Interleaved group requires epilogue iteration.\n");
+      RequiresScalarEpilogue = true;
+    }
+  }
 }
 
 LoopVectorizationCostModel::VectorizationFactor

llvm/test/Transforms/LoopVectorize/AArch64/gather-cost.ll

@@ -1,4 +1,4 @@
-; RUN: opt -loop-vectorize -mtriple=arm64-apple-ios -S -mcpu=cyclone < %s | FileCheck %s
+; RUN: opt -loop-vectorize -mtriple=arm64-apple-ios -S -mcpu=cyclone -enable-interleaved-mem-accesses=false < %s | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-n32:64-S128"
 
 @kernel = global [512 x float] zeroinitializer, align 16

llvm/test/Transforms/LoopVectorize/ARM/gather-cost.ll

@@ -1,4 +1,4 @@
-; RUN: opt -loop-vectorize -mtriple=thumbv7s-apple-ios6.0.0 -S < %s | FileCheck %s
+; RUN: opt -loop-vectorize -mtriple=thumbv7s-apple-ios6.0.0 -S -enable-interleaved-mem-accesses=false < %s | FileCheck %s
 
 target datalayout = "e-p:32:32:32-i1:8:32-i8:8:32-i16:16:32-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:32:64-v128:32:128-a0:0:32-n32-S32"
 

llvm/test/Transforms/LoopVectorize/X86/gather-cost.ll

@@ -1,4 +1,4 @@
-; RUN: opt -loop-vectorize -mtriple=x86_64-apple-macosx -S -mcpu=corei7-avx < %s | FileCheck %s
+; RUN: opt -loop-vectorize -mtriple=x86_64-apple-macosx -S -mcpu=corei7-avx -enable-interleaved-mem-accesses=false < %s | FileCheck %s
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 
 @kernel = global [512 x float] zeroinitializer, align 16

llvm/test/Transforms/LoopVectorize/interleaved-accesses-1.ll

@@ -0,0 +1,78 @@
+; RUN: opt -S -loop-vectorize -instcombine -force-vector-width=4 -force-vector-interleave=1 -enable-interleaved-mem-accesses=true < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; Check that the interleaved-mem-access analysis identifies the access
+; to array 'in' as interleaved, despite the possibly wrapping unsigned
+; 'out_ix' index.
+;
+; In this test the interleave-groups are full (have no gaps), so no wrapping
+; checks are necessary. We can call getPtrStride with Assume=false and
+; ShouldCheckWrap=false to safely figure out that the stride is 2.
+
+; #include <stdlib.h>
+; class Complex {
+; private:
+;  float real_;
+;  float imaginary_;
+;
+;public:
+; Complex() : real_(0), imaginary_(0) { }
+; Complex(float real, float imaginary) : real_(real), imaginary_(imaginary) { }
+; Complex(const Complex &rhs) : real_(rhs.real()), imaginary_(rhs.imaginary()) { }
+;
+; inline float real() const { return real_; }
+; inline float imaginary() const { return imaginary_; }
+;};
+;
+;void test(Complex * __restrict__ out, Complex * __restrict__ in, size_t out_start, size_t size)
+;{
+;   for (size_t out_offset = 0; out_offset < size; ++out_offset)
+;     {
+;       size_t out_ix = out_start + out_offset;
+;       Complex t0 = in[out_ix];
+;       out[out_ix] = t0;
+;     }
+;}
+
+; CHECK: vector.body:
+; CHECK: %wide.vec = load <8 x i32>, <8 x i32>* {{.*}}, align 4
+; CHECK: shufflevector <8 x i32> %wide.vec, <8 x i32> undef, <4 x i32> <i32 0, i32 2, i32 4, i32 6>
+; CHECK: shufflevector <8 x i32> %wide.vec, <8 x i32> undef, <4 x i32> <i32 1, i32 3, i32 5, i32 7>
+
+%class.Complex = type { float, float }
+
+define void @_Z4testP7ComplexS0_mm(%class.Complex* noalias nocapture %out, %class.Complex* noalias nocapture readonly %in, i64 %out_start, i64 %size) local_unnamed_addr {
+entry:
+  %cmp9 = icmp eq i64 %size, 0
+  br i1 %cmp9, label %for.cond.cleanup, label %for.body.preheader
+
+for.body.preheader:
+  br label %for.body
+
+for.cond.cleanup.loopexit:
+  br label %for.cond.cleanup
+
+for.cond.cleanup:
+  ret void
+
+for.body:
+  %out_offset.010 = phi i64 [ %inc, %for.body ], [ 0, %for.body.preheader ]
+  %add = add i64 %out_offset.010, %out_start
+  %arrayidx = getelementptr inbounds %class.Complex, %class.Complex* %in, i64 %add
+  %0 = bitcast %class.Complex* %arrayidx to i32*
+  %1 = load i32, i32* %0, align 4
+  %imaginary_.i.i = getelementptr inbounds %class.Complex, %class.Complex* %in, i64 %add, i32 1
+  %2 = bitcast float* %imaginary_.i.i to i32*
+  %3 = load i32, i32* %2, align 4
+  %arrayidx1 = getelementptr inbounds %class.Complex, %class.Complex* %out, i64 %add
+  %4 = bitcast %class.Complex* %arrayidx1 to i64*
+  %t0.sroa.4.0.insert.ext = zext i32 %3 to i64
+  %t0.sroa.4.0.insert.shift = shl nuw i64 %t0.sroa.4.0.insert.ext, 32
+  %t0.sroa.0.0.insert.ext = zext i32 %1 to i64
+  %t0.sroa.0.0.insert.insert = or i64 %t0.sroa.4.0.insert.shift, %t0.sroa.0.0.insert.ext
+  store i64 %t0.sroa.0.0.insert.insert, i64* %4, align 4
+  %inc = add nuw i64 %out_offset.010, 1
+  %exitcond = icmp eq i64 %inc, %size
+  br i1 %exitcond, label %for.cond.cleanup.loopexit, label %for.body
+}

llvm/test/Transforms/LoopVectorize/interleaved-accesses-2.ll

@@ -0,0 +1,58 @@
+; RUN: opt -S -loop-vectorize -instcombine -force-vector-width=4 -force-vector-interleave=1 -enable-interleaved-mem-accesses=true < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; Check that the interleaved-mem-access analysis currently does not create an 
+; interleave group for the access to array 'in' due to the possibly wrapping 
+; unsigned 'out_ix' index.
+;
+; In this test the interleave-group of the loads is not full (has gaps), so 
+; the wrapping checks are necessary. Here this cannot be done statically so 
+; runtime checks are needed, but with Assume=false getPtrStride cannot add 
+; runtime checks and as a result we can't create the interleave-group.
+;
+; FIXME: This is currently a missed optimization until we can use Assume=true 
+; with proper threshold checks. Once we do that the candidate interleave-group
+; will not be invalidated by the wrapping checks.
+
+; #include <stdlib.h>
+; void test(float * __restrict__ out, float * __restrict__ in, size_t size)
+; {
+;    for (size_t out_offset = 0; out_offset < size; ++out_offset)
+;      {
+;        float t0 = in[2*out_offset];
+;        out[out_offset] = t0;
+;      }
+; }
+
+; CHECK: vector.body:
+; CHECK-NOT: %wide.vec = load <8 x i32>, <8 x i32>* {{.*}}, align 4
+; CHECK-NOT: shufflevector <8 x i32> %wide.vec, <8 x i32> undef, <4 x i32> <i32 0, i32 2, i32 4, i32 6>
+
+define void @_Z4testPfS_m(float* noalias nocapture %out, float* noalias nocapture readonly %in, i64 %size) local_unnamed_addr {
+entry:
+  %cmp7 = icmp eq i64 %size, 0
+  br i1 %cmp7, label %for.cond.cleanup, label %for.body.preheader
+
+for.body.preheader:
+  br label %for.body
+
+for.cond.cleanup.loopexit:
+  br label %for.cond.cleanup
+
+for.cond.cleanup:
+  ret void
+
+for.body:
+  %out_offset.08 = phi i64 [ %inc, %for.body ], [ 0, %for.body.preheader ]
+  %mul = shl i64 %out_offset.08, 1
+  %arrayidx = getelementptr inbounds float, float* %in, i64 %mul
+  %0 = bitcast float* %arrayidx to i32*
+  %1 = load i32, i32* %0, align 4
+  %arrayidx1 = getelementptr inbounds float, float* %out, i64 %out_offset.08
+  %2 = bitcast float* %arrayidx1 to i32*
+  store i32 %1, i32* %2, align 4
+  %inc = add nuw i64 %out_offset.08, 1
+  %exitcond = icmp eq i64 %inc, %size
+  br i1 %exitcond, label %for.cond.cleanup.loopexit, label %for.body
+}

llvm/test/Transforms/LoopVectorize/interleaved-accesses-3.ll

@@ -0,0 +1,57 @@
+; RUN: opt -S -loop-vectorize -instcombine -force-vector-width=4 -force-vector-interleave=1 -enable-interleaved-mem-accesses=true < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; Check that the interleaved-mem-access analysis currently does not create an 
+; interleave group for access 'a' due to the possible pointer wrap-around.
+;
+; To begin with, in this test the candidate interleave group can be created 
+; only when getPtrStride is called with Assume=true. Next, because
+; the interleave-group of the loads is not full (has gaps), we also need to check 
+; for possible pointer wrapping. Here we currently use Assume=false and as a 
+; result cannot prove the transformation is safe and therefore invalidate the
+; candidate interleave group.
+;
+; FIXME: This is a missed optimization. Once we use Assume=true here, we will
+; not have to invalidate the group.
+
+; void func(unsigned * __restrict a, unsigned * __restrict b, unsigned char x, unsigned char y) {
+;  int i = 0;
+;  for (unsigned char index = x; i < y; index +=2, ++i)
+;    b[i] = a[index] * 2;
+;
+; }
+
+; CHECK: vector.body:
+; CHECK-NOT: %wide.vec = load <8 x i32>, <8 x i32>* {{.*}}, align 4
+; CHECK-NOT: shufflevector <8 x i32> %wide.vec, <8 x i32> undef, <4 x i32> <i32 0, i32 2, i32 4, i32 6>
+
+define void @_Z4funcPjS_hh(i32* noalias nocapture readonly %a, i32* noalias nocapture %b, i8 zeroext %x, i8 zeroext %y) local_unnamed_addr {
+entry:
+  %cmp9 = icmp eq i8 %y, 0
+  br i1 %cmp9, label %for.cond.cleanup, label %for.body.preheader
+
+for.body.preheader:
+  %wide.trip.count = zext i8 %y to i64
+  br label %for.body
+
+for.cond.cleanup.loopexit:
+  br label %for.cond.cleanup
+
+for.cond.cleanup:
+  ret void
+
+for.body:
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %for.body.preheader ]
+  %index.011 = phi i8 [ %add, %for.body ], [ %x, %for.body.preheader ]
+  %idxprom = zext i8 %index.011 to i64
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
+  %0 = load i32, i32* %arrayidx, align 4
+  %mul = shl i32 %0, 1
+  %arrayidx2 = getelementptr inbounds i32, i32* %b, i64 %indvars.iv
+  store i32 %mul, i32* %arrayidx2, align 4
+  %add = add i8 %index.011, 2
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp eq i64 %indvars.iv.next, %wide.trip.count
+  br i1 %exitcond, label %for.cond.cleanup.loopexit, label %for.body
+}