[CIR][CIRGen] Emit memcpys for copy constructors (#1197)

CodeGen does so for trivial record types as well as non-record types; we
only do it for non-record types.

Author: smeenai

clang/include/clang/CIR/MissingFeatures.h

@@ -141,7 +141,6 @@ struct MissingFeatures {
   static bool shouldSplitConstantStore() { return false; }
   static bool shouldCreateMemCpyFromGlobal() { return false; }
   static bool shouldReverseUnaryCondOnBoolExpr() { return false; }
-  static bool fieldMemcpyizerBuildMemcpy() { return false; }
   static bool isTrivialCtorOrDtor() { return false; }
   static bool isMemcpyEquivalentSpecialMember() { return false; }
   static bool constructABIArgDirectExtend() { return false; }

clang/lib/CIR/CodeGen/CIRGenClass.cpp

@@ -333,9 +333,23 @@ class ConstructorMemcpyizer : public FieldMemcpyizer {
   bool isMemberInitMemcpyable(CXXCtorInitializer *MemberInit) const {
     if (!MemcpyableCtor)
       return false;
+    FieldDecl *field = MemberInit->getMember();
+    assert(field && "No field for member init.");
+    QualType fieldType = field->getType();
+    CXXConstructExpr *ce = dyn_cast<CXXConstructExpr>(MemberInit->getInit());
+
+    // Bail out on any members of record type (unlike CodeGen, which emits a
+    // memcpy for trivially-copyable record types).
+    if (ce || (fieldType->isArrayType() &&
+               CGF.getContext().getBaseElementType(fieldType)->isRecordType()))
+      return false;
 
-    assert(!cir::MissingFeatures::fieldMemcpyizerBuildMemcpy());
-    return false;
+    // Bail out on volatile fields.
+    if (!isMemcpyableField(field))
+      return false;
+
+    // Otherwise we're good.
+    return true;
   }
 
 public:
@@ -363,7 +377,10 @@ class ConstructorMemcpyizer : public FieldMemcpyizer {
       // This memcpy is too small to be worthwhile. Fall back on default
       // codegen.
       if (!AggregatedInits.empty()) {
-        llvm_unreachable("NYI");
+        CopyingValueRepresentation cvr(CGF);
+        emitMemberInitializer(CGF, ConstructorDecl->getParent(),
+                              AggregatedInits[0], ConstructorDecl, Args);
+        AggregatedInits.clear();
       }
       reset();
       return;
@@ -375,21 +392,14 @@ class ConstructorMemcpyizer : public FieldMemcpyizer {
   }
 
   void pushEHDestructors() {
-    Address ThisPtr = CGF.LoadCXXThisAddress();
-    QualType RecordTy = CGF.getContext().getTypeDeclType(ClassDecl);
-    LValue LHS = CGF.makeAddrLValue(ThisPtr, RecordTy);
-    (void)LHS;
-
-    for (unsigned i = 0; i < AggregatedInits.size(); ++i) {
-      CXXCtorInitializer *MemberInit = AggregatedInits[i];
-      QualType FieldType = MemberInit->getAnyMember()->getType();
-      QualType::DestructionKind dtorKind = FieldType.isDestructedType();
-      if (!CGF.needsEHCleanup(dtorKind))
-        continue;
-      LValue FieldLHS = LHS;
-      emitLValueForAnyFieldInitialization(CGF, MemberInit, FieldLHS);
-      CGF.pushEHDestroy(dtorKind, FieldLHS.getAddress(), FieldType);
+#ifndef NDEBUG
+    for (CXXCtorInitializer *memberInit : AggregatedInits) {
+      QualType fieldType = memberInit->getAnyMember()->getType();
+      QualType::DestructionKind dtorKind = fieldType.isDestructedType();
+      assert(!CGF.needsEHCleanup(dtorKind) &&
+             "Non-record types shouldn't need EH cleanup");
     }
+#endif
   }
 
   void finish() { emitAggregatedInits(); }

clang/test/CIR/CodeGen/copy-constructor.cpp

@@ -33,3 +33,55 @@ struct HasScalarArrayMember {
 // LLVM-NEXT:    call void @llvm.memcpy.p0.p0.i32(ptr %[[#THIS_ARR]], ptr %[[#OTHER_ARR]], i32 16, i1 false)
 // LLVM-NEXT:    ret void
 HasScalarArrayMember::HasScalarArrayMember(const HasScalarArrayMember &) = default;
+
+struct Trivial { int *i; };
+struct ManyMembers {
+  int i;
+  int j;
+  Trivial k;
+  int l[1];
+  int m[2];
+  Trivial n;
+  int &o;
+  int *p;
+};
+
+// CIR-LABEL: cir.func linkonce_odr @_ZN11ManyMembersC2ERKS_(
+// CIR:         %[[#THIS_LOAD:]] = cir.load %[[#]]
+// CIR-NEXT:    %[[#THIS_I:]] = cir.get_member %[[#THIS_LOAD]][0] {name = "i"}
+// CIR-NEXT:    %[[#OTHER_LOAD:]] = cir.load %[[#OTHER:]]
+// CIR-NEXT:    %[[#OTHER_I:]] = cir.get_member %[[#OTHER_LOAD]][0] {name = "i"}
+// CIR-NEXT:    %[[#MEMCPY_SIZE:]] = cir.const #cir.int<8>
+// CIR-NEXT:    %[[#THIS_I_CAST:]] = cir.cast(bitcast, %[[#THIS_I]] : !cir.ptr<!s32i>), !cir.ptr<!void>
+// CIR-NEXT:    %[[#OTHER_I_CAST:]] = cir.cast(bitcast, %[[#OTHER_I]] : !cir.ptr<!s32i>), !cir.ptr<!void>
+// CIR-NEXT:    cir.libc.memcpy %[[#MEMCPY_SIZE]] bytes from %[[#OTHER_I_CAST]] to %[[#THIS_I_CAST]]
+// CIR-NEXT:    %[[#THIS_K:]] = cir.get_member %[[#THIS_LOAD]][2] {name = "k"}
+// CIR-NEXT:    %[[#OTHER_LOAD:]] = cir.load %[[#OTHER]]
+// CIR-NEXT:    %[[#OTHER_K:]] = cir.get_member %[[#OTHER_LOAD]][2] {name = "k"}
+// CIR-NEXT:    cir.call @_ZN7TrivialC1ERKS_(%[[#THIS_K]], %[[#OTHER_K]])
+// CIR-NEXT:    %[[#THIS_L:]] = cir.get_member %[[#THIS_LOAD]][3] {name = "l"}
+// CIR-NEXT:    %[[#OTHER_LOAD:]] = cir.load %[[#OTHER]]
+// CIR-NEXT:    %[[#OTHER_L:]] = cir.get_member %[[#OTHER_LOAD]][3] {name = "l"}
+// CIR-NEXT:    %[[#MEMCPY_SIZE:]] = cir.const #cir.int<12>
+// CIR-NEXT:    %[[#THIS_L_CAST:]] = cir.cast(bitcast, %[[#THIS_L]] : !cir.ptr<!cir.array<!s32i x 1>>), !cir.ptr<!void>
+// CIR-NEXT:    %[[#OTHER_L_CAST:]] = cir.cast(bitcast, %[[#OTHER_L]] : !cir.ptr<!cir.array<!s32i x 1>>), !cir.ptr<!void>
+// CIR-NEXT:    cir.libc.memcpy %[[#MEMCPY_SIZE]] bytes from %[[#OTHER_L_CAST]] to %[[#THIS_L_CAST]]
+// CIR-NEXT:    %[[#THIS_N:]] = cir.get_member %[[#THIS_LOAD]][5] {name = "n"}
+// CIR-NEXT:    %[[#OTHER_LOAD:]] = cir.load %[[#OTHER]]
+// CIR-NEXT:    %[[#OTHER_N:]] = cir.get_member %[[#OTHER_LOAD]][5] {name = "n"}
+// CIR-NEXT:    cir.call @_ZN7TrivialC1ERKS_(%[[#THIS_N]], %[[#OTHER_N]])
+// CIR-NEXT:    %[[#THIS_O:]] = cir.get_member %[[#THIS_LOAD]][6] {name = "o"}
+// CIR-NEXT:    %[[#OTHER_LOAD:]] = cir.load %[[#OTHER]]
+// CIR-NEXT:    %[[#OTHER_O:]] = cir.get_member %[[#OTHER_LOAD]][6] {name = "o"}
+// CIR-NEXT:    %[[#MEMCPY_SIZE:]] = cir.const #cir.int<16>
+// CIR-NEXT:    %[[#THIS_O_CAST:]] = cir.cast(bitcast, %[[#THIS_O]] : !cir.ptr<!cir.ptr<!s32i>>), !cir.ptr<!void>
+// CIR-NEXT:    %[[#OTHER_O_CAST:]] = cir.cast(bitcast, %[[#OTHER_O]] : !cir.ptr<!cir.ptr<!s32i>>), !cir.ptr<!void>
+// CIR-NEXT:    cir.libc.memcpy %[[#MEMCPY_SIZE]] bytes from %[[#OTHER_O_CAST]] to %[[#THIS_O_CAST]]
+// CIR-NEXT:    cir.return
+// CIR-NEXT:  }
+
+// CIR-LABEL: cir.func @_Z6doCopyR11ManyMembers(
+// CIR:         cir.call @_ZN11ManyMembersC1ERKS_(
+ManyMembers doCopy(ManyMembers &src) {
+  return src;
+}