AtomicExpand: Preserve metadata when expanding partword RMW

This will be important for AMDGPU in a future patch.

Author: arsenm

llvm/lib/CodeGen/AtomicExpandPass.cpp

@@ -950,7 +950,10 @@ AtomicRMWInst *AtomicExpandImpl::widenPartwordAtomicRMW(AtomicRMWInst *AI) {
   AtomicRMWInst *NewAI = Builder.CreateAtomicRMW(
       Op, PMV.AlignedAddr, NewOperand, PMV.AlignedAddrAlignment,
       AI->getOrdering(), AI->getSyncScopeID());
-  // TODO: Preserve metadata
+
+  // TODO: Do we need to drop noundef? We widened the operation and could be
+  // loading undefined bits.
+  NewAI->copyMetadata(*AI);
 
   Value *FinalOldResult = extractMaskedValue(Builder, NewAI, PMV);
   AI->replaceAllUsesWith(FinalOldResult);

llvm/test/Transforms/AtomicExpand/AMDGPU/expand-atomic-i16.ll

@@ -189,7 +189,7 @@ define i16 @test_atomicrmw_and_i16_global_agent_preserve_md(ptr addrspace(1) %pt
 ; CHECK-NEXT:    [[TMP3:%.*]] = zext i16 [[VALUE:%.*]] to i32
 ; CHECK-NEXT:    [[VALOPERAND_SHIFTED:%.*]] = shl i32 [[TMP3]], [[SHIFTAMT]]
 ; CHECK-NEXT:    [[ANDOPERAND:%.*]] = or i32 [[VALOPERAND_SHIFTED]], [[INV_MASK]]
-; CHECK-NEXT:    [[TMP4:%.*]] = atomicrmw and ptr addrspace(1) [[ALIGNEDADDR]], i32 [[ANDOPERAND]] syncscope("agent") seq_cst, align 4
+; CHECK-NEXT:    [[TMP4:%.*]] = atomicrmw and ptr addrspace(1) [[ALIGNEDADDR]], i32 [[ANDOPERAND]] syncscope("agent") seq_cst, align 4, !noundef [[META0:![0-9]+]], !some.unknown.md [[META0]]
 ; CHECK-NEXT:    [[SHIFTED:%.*]] = lshr i32 [[TMP4]], [[SHIFTAMT]]
 ; CHECK-NEXT:    [[EXTRACTED:%.*]] = trunc i32 [[SHIFTED]] to i16
 ; CHECK-NEXT:    ret i16 [[EXTRACTED]]
@@ -204,7 +204,7 @@ define i16 @test_atomicrmw_and_i16_global_agent_align4_preserve_md(ptr addrspace
 ; CHECK-LABEL: @test_atomicrmw_and_i16_global_agent_align4_preserve_md(
 ; CHECK-NEXT:    [[TMP1:%.*]] = zext i16 [[VALUE:%.*]] to i32
 ; CHECK-NEXT:    [[ANDOPERAND:%.*]] = or i32 [[TMP1]], -65536
-; CHECK-NEXT:    [[TMP2:%.*]] = atomicrmw and ptr addrspace(1) [[PTR:%.*]], i32 [[ANDOPERAND]] syncscope("agent") seq_cst, align 4
+; CHECK-NEXT:    [[TMP2:%.*]] = atomicrmw and ptr addrspace(1) [[PTR:%.*]], i32 [[ANDOPERAND]] syncscope("agent") seq_cst, align 4, !noundef [[META0]], !some.unknown.md [[META0]]
 ; CHECK-NEXT:    [[EXTRACTED:%.*]] = trunc i32 [[TMP2]] to i16
 ; CHECK-NEXT:    ret i16 [[EXTRACTED]]
 ;