Fix broken invariant

[gchatelet]

Summary

A Copy with a source that is zeros is the same as a Set of zeros.
This fixes the invariant that SrcAlign should always be non-null.

[gchatelet]

• Added asserts

[courbet]

llvm/include/llvm/CodeGen/TargetLowering.h

128 ↗

(On Diff #241756)

destination alignment

129 ↗

(On Diff #241756)

source alignment

[gchatelet]

Fixed assert messages

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

if (FI && !MFI.isFixedObjectIndex(FI->getIndex()))
     DstAlignCanChange = true;
   unsigned SrcAlign = DAG.InferPtrAlignment(Src);
   if (Alignment > SrcAlign)
     SrcAlign = Alignment;
   ConstantDataArraySlice Slice;
   bool CopyFromConstant = isMemSrcFromConstant(Src, Slice);
   bool isZeroConstant = CopyFromConstant && Slice.Array == nullptr;
   unsigned Limit = AlwaysInline ? ~0U : TLI.getMaxStoresPerMemcpy(OptSize);
+  const MemOp Op = isZeroConstant
+                       ? MemOp::Set(Size, DstAlignCanChange, Alignment,
+                                    /*IsZeroMemset*/ true, isVol)
+                       : MemOp::Copy(Size, DstAlignCanChange, Alignment,
+                                     SrcAlign, isVol, CopyFromConstant);
   if (!TLI.findOptimalMemOpLowering(
-          MemOps, Limit,
-          MemOp::Copy(Size, DstAlignCanChange, Alignment,
-                      isZeroConstant ? 0 : SrcAlign, isVol, CopyFromConstant),
-          DstPtrInfo.getAddrSpace(), SrcPtrInfo.getAddrSpace(),
-          MF.getFunction().getAttributes()))
+          MemOps, Limit, Op, DstPtrInfo.getAddrSpace(),
+          SrcPtrInfo.getAddrSpace(), MF.getFunction().getAttributes()))
     return SDValue();
 
   if (DstAlignCanChange) {
     Type *Ty = MemOps[0].getTypeForEVT(C);
     unsigned NewAlign = (unsigned)DL.getABITypeAlignment(Ty);
 
     // Don't promote to an alignment that would require dynamic stack
     // realignment.

llvm/test/CodeGen/AArch64/memcpy-f128.ll

 ; RUN: llc < %s -mtriple=aarch64-linux-gnu | FileCheck %s
 
 %structA = type { i128 }
 @stubA = internal unnamed_addr constant %structA zeroinitializer, align 8
 
 ; Make sure we don't hit llvm_unreachable.
 
 define void @test1() {
 ; CHECK-LABEL: @test1
-; CHECK: adrp
-; CHECK: ldr q0
-; CHECK: str q0
 ; CHECK: ret
 entry:
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 undef, i8* align 8 bitcast (%structA* @stubA to i8*), i64 48, i1 false)
   ret void
 }
 
 declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i1)