[InstCombine][SVE] Bail out of isSafeToLoadUnconditionally for scalable types

[peterwaller-arm]

Summary

isSafeToLoadUnconditionally currently assumes sized types. Bail out for now.
This fixes a TypeSize warning reachable from instcombine via (load (select
cond, ptr, ptr)).

[david-arm]

llvm/lib/Analysis/Loads.cpp

411

Here you're still relying upon the implicit cast from TypeSize->uint64_t, which we're trying to avoid. I think it's better to write this explicitly as:

APInt Size(DL.getIndexTypeSizeInBits(V->getType()), TySize.getFixedValue());

llvm/test/Transforms/InstCombine/scalable-select.ll

20

This test is missing some CHECK lines

[peterwaller-arm]

Address review comments: Run test checks, use TySize.getFixedValue()

[david-arm]

LGTM! Merci!

llvm/lib/Analysis/Loads.cpp

bool llvm::isSafeToLoadUnconditionally(Value *V, Align Alignment, APInt &Size,
   return false;
 }
 
 bool llvm::isSafeToLoadUnconditionally(Value *V, Type *Ty, Align Alignment,
                                        const DataLayout &DL,
                                        Instruction *ScanFrom,
                                        const DominatorTree *DT,
                                        const TargetLibraryInfo *TLI) {
-  APInt Size(DL.getIndexTypeSizeInBits(V->getType()), DL.getTypeStoreSize(Ty));
+  TypeSize TySize = DL.getTypeStoreSize(Ty);
+  if (TySize.isScalable())
+    return false;
+  APInt Size(DL.getIndexTypeSizeInBits(V->getType()), TySize.getFixedValue());
   return isSafeToLoadUnconditionally(V, Alignment, Size, DL, ScanFrom, DT, TLI);
 }
 
 /// DefMaxInstsToScan - the default number of maximum instructions
 /// to scan in the block, used by FindAvailableLoadedValue().
 /// FindAvailableLoadedValue() was introduced in r60148, to improve jump
 /// threading in part by eliminating partially redundant loads.
 /// At that point, the value of MaxInstsToScan was already set to '6'

llvm/test/Transforms/InstCombine/scalable-select.ll

 ; CHECK-NEXT:    ret <vscale x 1 x i32> [[D]]
 ;
   %head = insertelement <vscale x 1 x i32> undef, i32 2, i32 0
   %splat = shufflevector <vscale x 1 x i32> %head, <vscale x 1 x i32> undef, <vscale x 1 x i32> zeroinitializer
   %c = add nsw <vscale x 1 x i32> %b, %splat
   %d = select <vscale x 1 x i1> %m, <vscale x 1 x i32> %c, <vscale x 1 x i32> %b
   ret <vscale x 1 x i32> %d
 }
+
+define <vscale x 2 x i64> @load_scalable_of_selected_ptrs(ptr %p0, ptr %p1, i64 %idx) {
+; CHECK-LABEL: @load_scalable_of_selected_ptrs(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[ARRAYIDX0:%.*]] = getelementptr inbounds i32, ptr [[P0:%.*]], i64 [[IDX:%.*]]
+; CHECK-NEXT:    [[ARRAYIDX1:%.*]] = getelementptr inbounds i32, ptr [[P1:%.*]], i64 [[IDX]]
+; CHECK-NEXT:    [[L0:%.*]] = load i32, ptr [[ARRAYIDX0]], align 4
+; CHECK-NEXT:    [[L1:%.*]] = load i32, ptr [[ARRAYIDX1]], align 4
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[L0]], [[L1]]
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], ptr [[ARRAYIDX0]], ptr [[ARRAYIDX1]]
+; CHECK-NEXT:    [[RET:%.*]] = load <vscale x 2 x i64>, ptr [[SEL]], align 16
+; CHECK-NEXT:    ret <vscale x 2 x i64> [[RET]]
+;
+entry:
+  ; Test introduced in response to a TypeSize warning arising from isSafeToLoadUnconditionally via instcombine.
+  ; deref (p0[0] < p1[0] ? p0 : p1) as <vscale x 2 x i64>.
+  %arrayidx0 = getelementptr inbounds i32, ptr %p0, i64 %idx
+  %arrayidx1 = getelementptr inbounds i32, ptr %p1, i64 %idx
+  %l0 = load i32, ptr %arrayidx0
+  %l1 = load i32, ptr %arrayidx1
+  %cmp = icmp slt i32 %l0, %l1
+  %sel = select i1 %cmp, ptr %arrayidx0, ptr %arrayidx1
+  %ret = load <vscale x 2 x i64>, ptr %sel
+  ret <vscale x 2 x i64> %ret
+}