[InstCombine] Skip scalable vectors in combineLoadToOperationType

Don't try to canonicalize loads to scalable vector types to loads
of integers.

This removes one assertion when trying to use a TypeSize as a parameter
to DataLayout::isLegalInteger. It does not handle the second part of the
function (which looks at bitcasts).

This patch also contains a NFC fix for Load Analysis, where a variable
initialization that would cause the same assertion is moved closer to
its use. This allows us to run the new test for InstCombine without
having to teach LocationSize to play nicely with scalable vectors.

Differential Revision: https://reviews.llvm.org/D70075

llvm/lib/Analysis/Loads.cpp

@@ -383,10 +383,6 @@ Value *llvm::FindAvailablePtrLoadStore(Value *Ptr, Type *AccessTy,
     MaxInstsToScan = ~0U;
 
   const DataLayout &DL = ScanBB->getModule()->getDataLayout();
-
-  // Try to get the store size for the type.
-  auto AccessSize = LocationSize::precise(DL.getTypeStoreSize(AccessTy));
-
   Value *StrippedPtr = Ptr->stripPointerCasts();
 
   while (ScanFrom != ScanBB->begin()) {
@@ -425,6 +421,9 @@ Value *llvm::FindAvailablePtrLoadStore(Value *Ptr, Type *AccessTy,
         return LI;
       }
 
+    // Try to get the store size for the type.
+    auto AccessSize = LocationSize::precise(DL.getTypeStoreSize(AccessTy));
+
     if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
       Value *StorePtr = SI->getPointerOperand()->stripPointerCasts();
       // If this is a store through Ptr, the value is available!

llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp

@@ -586,6 +586,7 @@ static Instruction *combineLoadToOperationType(InstCombiner &IC, LoadInst &LI) {
   // Do not perform canonicalization if minmax pattern is found (to avoid
   // infinite loop).
   if (!Ty->isIntegerTy() && Ty->isSized() &&
+      !(Ty->isVectorTy() && Ty->getVectorIsScalable()) &&
       DL.isLegalInteger(DL.getTypeStoreSizeInBits(Ty)) &&
       DL.typeSizeEqualsStoreSize(Ty) &&
       !DL.isNonIntegralPointerType(Ty) &&

llvm/test/Transforms/InstCombine/load.ll

@@ -237,6 +237,42 @@ entry:
   ret void
 }
 
+define void @test16-vect(i8* %x, i8* %a, i8* %b, i8* %c) {
+; CHECK-LABEL: @test16-vect(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[C_CAST:%.*]] = bitcast i8* [[C:%.*]] to i32*
+; CHECK-NEXT:    [[TMP0:%.*]] = bitcast i8* [[X:%.*]] to i32*
+; CHECK-NEXT:    [[X11:%.*]] = load i32, i32* [[TMP0]], align 4
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast i8* [[A:%.*]] to i32*
+; CHECK-NEXT:    store i32 [[X11]], i32* [[TMP1]], align 4
+; CHECK-NEXT:    [[TMP2:%.*]] = bitcast i8* [[B:%.*]] to i32*
+; CHECK-NEXT:    store i32 [[X11]], i32* [[TMP2]], align 4
+; CHECK-NEXT:    [[TMP3:%.*]] = bitcast i8* [[X]] to i32*
+; CHECK-NEXT:    [[X22:%.*]] = load i32, i32* [[TMP3]], align 4
+; CHECK-NEXT:    [[TMP4:%.*]] = bitcast i8* [[B]] to i32*
+; CHECK-NEXT:    store i32 [[X22]], i32* [[TMP4]], align 4
+; CHECK-NEXT:    store i32 [[X22]], i32* [[C_CAST]], align 4
+; CHECK-NEXT:    ret void
+;
+entry:
+  %x.cast = bitcast i8* %x to <4 x i8>*
+  %a.cast = bitcast i8* %a to <4 x i8>*
+  %b.cast = bitcast i8* %b to <4 x i8>*
+  %c.cast = bitcast i8* %c to i32*
+
+  %x1 = load <4 x i8>, <4 x i8>* %x.cast
+  store <4 x i8> %x1, <4 x i8>* %a.cast
+  store <4 x i8> %x1, <4 x i8>* %b.cast
+
+  %x2 = load <4 x i8>, <4 x i8>* %x.cast
+  store <4 x i8> %x2, <4 x i8>* %b.cast
+  %x2.cast = bitcast <4 x i8> %x2 to i32
+  store i32 %x2.cast, i32* %c.cast
+
+  ret void
+}
+
+
 ; Check that in cases similar to @test16 we don't try to rewrite a load when
 ; its only use is a store but it is used as the pointer to that store rather
 ; than the value.
@@ -300,3 +336,15 @@ entry:
   store %swift.error* %err.res, %swift.error** %err, align 8
   ret void
 }
+
+; Make sure we don't canonicalize accesses to scalable vectors.
+define void @test20(<vscale x 4 x i8>* %x, <vscale x 4 x i8>* %y) {
+; CHECK-LABEL: @test20(
+; CHECK-NEXT:    [[X_LOAD:%.*]] = load <vscale x 4 x i8>, <vscale x 4 x i8>* [[X:%.*]], align 1
+; CHECK-NEXT:    store <vscale x 4 x i8> [[X_LOAD]], <vscale x 4 x i8>* [[Y:%.*]], align 1
+; CHECK-NEXT:    ret void
+;
+  %x.load = load <vscale x 4 x i8>, <vscale x 4 x i8>* %x, align 1
+  store <vscale x 4 x i8> %x.load, <vscale x 4 x i8>* %y, align 1
+  ret void
+}