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

destination alignment

129

source alignment

[gchatelet]

Fixed assert messages

llvm/include/llvm/CodeGen/TargetLowering.h

struct MemOp {
   bool MemcpyStrSrc; // Indicates whether the memcpy source is an in-register
                      // constant so it does not need to be loaded.
   unsigned SrcAlign; // Inferred alignment of the source or zero if the memory
                      // operation does not need to load the value.
 
   static MemOp Copy(uint64_t Size, bool DstAlignCanChange, unsigned DstAlign,
                     unsigned SrcAlign, bool IsVolatile,
                     bool MemcpyStrSrc = false) {
+    assert(DstAlign && "Destination alignment should be set");
+    assert(SrcAlign && "Source alignment should be set");
     return {
         /*.Size =*/Size,
         /*.DstAlign =*/DstAlignCanChange ? 0 : DstAlign,
         /*.AllowOverlap =*/!IsVolatile,
         /*.IsMemset =*/false,
         /*.ZeroMemset =*/false,
         /*.MemcpyStrSrc =*/MemcpyStrSrc,
         /*.SrcAlign =*/SrcAlign,
     };
   }
   static MemOp Set(uint64_t Size, bool DstAlignCanChange, unsigned DstAlign,
                    bool IsZeroMemset, bool IsVolatile) {
+    assert(DstAlign && "Destination alignment should be set");
     return {
         /*.Size =*/Size,
         /*.DstAlign =*/DstAlignCanChange ? 0 : DstAlign,
         /*.AllowOverlap =*/!IsVolatile,
         /*.IsMemset =*/true,
         /*.ZeroMemset =*/IsZeroMemset,
         /*.MemcpyStrSrc =*/false,
         /*.SrcAlign =*/0,

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)