[clang][FMV] Do not omit explicit default target_version attribute. (#96628)

Fixes a crash and cleans up some dead code.

namespace Foo {
int bar();
__attribute((target_version("default"))) int bar() { return 0; }
__attribute((target_version("mops"))) int bar() { return 1; }
}

$ clang++ --target=aarch64-linux-gnu --rtlib=compiler-rt fmv.cpp

None multiversion type isn't valid here
UNREACHABLE executed at clang/lib/CodeGen/CodeGenModule.cpp:1840! ...
getMangledNameImpl
clang::CodeGen::CodeGenModule::getMangledName
clang::CodeGen::CodeGenModule::EmitGlobal

3 files changed, 97 insertions, 58 deletions

diff --git a/clang/test/CodeGen/attr-target-version.c b/clang/test/CodeGen/attr-target-version.c
index 024aaff..4edfc54 100644
--- a/clang/test/CodeGen/attr-target-version.c
+++ b/clang/test/CodeGen/attr-target-version.c
@@ -428,13 +428,6 @@ int caller(void) { return used_def_without_default_decl() + used_decl_without_de
 //
 //
 // CHECK: Function Attrs: noinline nounwind optnone
-// CHECK-LABEL: define {{[^@]+}}@fmv_default
-// CHECK-SAME: () #[[ATTR11]] {
-// CHECK-NEXT:  entry:
-// CHECK-NEXT:    ret i32 111
-//
-//
-// CHECK: Function Attrs: noinline nounwind optnone
 // CHECK-LABEL: define {{[^@]+}}@fmv_c._Mssbs
 // CHECK-SAME: () #[[ATTR11]] {
 // CHECK-NEXT:  entry:
@@ -637,22 +630,18 @@ int caller(void) { return used_def_without_default_decl() + used_decl_without_de
 //
 //
 // CHECK: Function Attrs: noinline nounwind optnone
-// CHECK-LABEL: define {{[^@]+}}@recur
+// CHECK-LABEL: define {{[^@]+}}@fmv_default
 // CHECK-SAME: () #[[ATTR11]] {
 // CHECK-NEXT:  entry:
-// CHECK-NEXT:    call void @reca()
-// CHECK-NEXT:    ret void
+// CHECK-NEXT:    ret i32 111
 //
 //
 // CHECK: Function Attrs: noinline nounwind optnone
-// CHECK-LABEL: define {{[^@]+}}@main
+// CHECK-LABEL: define {{[^@]+}}@recur
 // CHECK-SAME: () #[[ATTR11]] {
 // CHECK-NEXT:  entry:
-// CHECK-NEXT:    [[RETVAL:%.*]] = alloca i32, align 4
-// CHECK-NEXT:    store i32 0, ptr [[RETVAL]], align 4
-// CHECK-NEXT:    call void @recur()
-// CHECK-NEXT:    [[CALL:%.*]] = call i32 @goo()
-// CHECK-NEXT:    ret i32 [[CALL]]
+// CHECK-NEXT:    call void @reca()
+// CHECK-NEXT:    ret void
 //
 //
 // CHECK: Function Attrs: noinline nounwind optnone
@@ -818,6 +807,17 @@ int caller(void) { return used_def_without_default_decl() + used_decl_without_de
 //
 //
 // CHECK: Function Attrs: noinline nounwind optnone
+// CHECK-LABEL: define {{[^@]+}}@main
+// CHECK-SAME: () #[[ATTR11]] {
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[RETVAL:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    store i32 0, ptr [[RETVAL]], align 4
+// CHECK-NEXT:    call void @recur()
+// CHECK-NEXT:    [[CALL:%.*]] = call i32 @goo()
+// CHECK-NEXT:    ret i32 [[CALL]]
+//
+//
+// CHECK: Function Attrs: noinline nounwind optnone
 // CHECK-LABEL: define {{[^@]+}}@fmv_inline._Mf64mmMpmullMsha1
 // CHECK-SAME: () #[[ATTR22:[0-9]+]] {
 // CHECK-NEXT:  entry:
@@ -1020,20 +1020,6 @@ int caller(void) { return used_def_without_default_decl() + used_decl_without_de
 //
 //
 // CHECK-NOFMV: Function Attrs: noinline nounwind optnone
-// CHECK-NOFMV-LABEL: define {{[^@]+}}@fmv_default
-// CHECK-NOFMV-SAME: () #[[ATTR0]] {
-// CHECK-NOFMV-NEXT:  entry:
-// CHECK-NOFMV-NEXT:    ret i32 111
-//
-//
-// CHECK-NOFMV: Function Attrs: noinline nounwind optnone
-// CHECK-NOFMV-LABEL: define {{[^@]+}}@fmv_c
-// CHECK-NOFMV-SAME: () #[[ATTR0]] {
-// CHECK-NOFMV-NEXT:  entry:
-// CHECK-NOFMV-NEXT:    ret void
-//
-//
-// CHECK-NOFMV: Function Attrs: noinline nounwind optnone
 // CHECK-NOFMV-LABEL: define {{[^@]+}}@goo
 // CHECK-NOFMV-SAME: () #[[ATTR0]] {
 // CHECK-NOFMV-NEXT:  entry:
@@ -1053,22 +1039,25 @@ int caller(void) { return used_def_without_default_decl() + used_decl_without_de
 //
 //
 // CHECK-NOFMV: Function Attrs: noinline nounwind optnone
-// CHECK-NOFMV-LABEL: define {{[^@]+}}@recur
+// CHECK-NOFMV-LABEL: define {{[^@]+}}@fmv_c
 // CHECK-NOFMV-SAME: () #[[ATTR0]] {
 // CHECK-NOFMV-NEXT:  entry:
-// CHECK-NOFMV-NEXT:    call void @reca()
 // CHECK-NOFMV-NEXT:    ret void
 //
 //
 // CHECK-NOFMV: Function Attrs: noinline nounwind optnone
-// CHECK-NOFMV-LABEL: define {{[^@]+}}@main
+// CHECK-NOFMV-LABEL: define {{[^@]+}}@fmv_default
 // CHECK-NOFMV-SAME: () #[[ATTR0]] {
 // CHECK-NOFMV-NEXT:  entry:
-// CHECK-NOFMV-NEXT:    [[RETVAL:%.*]] = alloca i32, align 4
-// CHECK-NOFMV-NEXT:    store i32 0, ptr [[RETVAL]], align 4
-// CHECK-NOFMV-NEXT:    call void @recur()
-// CHECK-NOFMV-NEXT:    [[CALL:%.*]] = call i32 @goo()
-// CHECK-NOFMV-NEXT:    ret i32 [[CALL]]
+// CHECK-NOFMV-NEXT:    ret i32 111
+//
+//
+// CHECK-NOFMV: Function Attrs: noinline nounwind optnone
+// CHECK-NOFMV-LABEL: define {{[^@]+}}@recur
+// CHECK-NOFMV-SAME: () #[[ATTR0]] {
+// CHECK-NOFMV-NEXT:  entry:
+// CHECK-NOFMV-NEXT:    call void @reca()
+// CHECK-NOFMV-NEXT:    ret void
 //
 //
 // CHECK-NOFMV: Function Attrs: noinline nounwind optnone
@@ -1089,31 +1078,42 @@ int caller(void) { return used_def_without_default_decl() + used_decl_without_de
 //
 //
 // CHECK-NOFMV: Function Attrs: noinline nounwind optnone
-// CHECK-NOFMV-LABEL: define {{[^@]+}}@unused_with_default_def
+// CHECK-NOFMV-LABEL: define {{[^@]+}}@unused_with_implicit_default_def
 // CHECK-NOFMV-SAME: () #[[ATTR0]] {
 // CHECK-NOFMV-NEXT:  entry:
 // CHECK-NOFMV-NEXT:    ret i32 1
 //
 //
 // CHECK-NOFMV: Function Attrs: noinline nounwind optnone
-// CHECK-NOFMV-LABEL: define {{[^@]+}}@unused_with_implicit_default_def
+// CHECK-NOFMV-LABEL: define {{[^@]+}}@unused_with_implicit_forward_default_def
 // CHECK-NOFMV-SAME: () #[[ATTR0]] {
 // CHECK-NOFMV-NEXT:  entry:
-// CHECK-NOFMV-NEXT:    ret i32 1
+// CHECK-NOFMV-NEXT:    ret i32 0
 //
 //
 // CHECK-NOFMV: Function Attrs: noinline nounwind optnone
-// CHECK-NOFMV-LABEL: define {{[^@]+}}@unused_with_implicit_forward_default_def
+// CHECK-NOFMV-LABEL: define {{[^@]+}}@default_def_with_version_decls
 // CHECK-NOFMV-SAME: () #[[ATTR0]] {
 // CHECK-NOFMV-NEXT:  entry:
 // CHECK-NOFMV-NEXT:    ret i32 0
 //
 //
 // CHECK-NOFMV: Function Attrs: noinline nounwind optnone
-// CHECK-NOFMV-LABEL: define {{[^@]+}}@default_def_with_version_decls
+// CHECK-NOFMV-LABEL: define {{[^@]+}}@main
 // CHECK-NOFMV-SAME: () #[[ATTR0]] {
 // CHECK-NOFMV-NEXT:  entry:
-// CHECK-NOFMV-NEXT:    ret i32 0
+// CHECK-NOFMV-NEXT:    [[RETVAL:%.*]] = alloca i32, align 4
+// CHECK-NOFMV-NEXT:    store i32 0, ptr [[RETVAL]], align 4
+// CHECK-NOFMV-NEXT:    call void @recur()
+// CHECK-NOFMV-NEXT:    [[CALL:%.*]] = call i32 @goo()
+// CHECK-NOFMV-NEXT:    ret i32 [[CALL]]
+//
+//
+// CHECK-NOFMV: Function Attrs: noinline nounwind optnone
+// CHECK-NOFMV-LABEL: define {{[^@]+}}@unused_with_default_def
+// CHECK-NOFMV-SAME: () #[[ATTR0]] {
+// CHECK-NOFMV-NEXT:  entry:
+// CHECK-NOFMV-NEXT:    ret i32 1
 //
 //.
 // CHECK: attributes #[[ATTR0]] = { noinline nounwind optnone "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-features"="+flagm,+fp-armv8,+fp16fml,+fullfp16,+neon,+rand,-v9.5a" }
diff --git a/clang/test/CodeGenCXX/fmv-namespace.cpp b/clang/test/CodeGenCXX/fmv-namespace.cpp
index 193f01d..abfff1a 100644
--- a/clang/test/CodeGenCXX/fmv-namespace.cpp
+++ b/clang/test/CodeGenCXX/fmv-namespace.cpp
@@ -17,25 +17,26 @@ int __attribute((target_version("sve"))) foo() { return 2; }
 
 int baz() { return OtherName::foo(); }
 
+namespace Foo {
+int bar();
+__attribute((target_version("default"))) int bar() { return 0; }
+__attribute((target_version("mops"))) int bar() { return 1; }
+}
+
 //.
 // CHECK: @__aarch64_cpu_features = external dso_local global { i64 }
 // CHECK: @_ZN4Name3fooEv = weak_odr ifunc i32 (), ptr @_ZN4Name3fooEv.resolver
 // CHECK: @_ZN9OtherName3fooEv = weak_odr ifunc i32 (), ptr @_ZN9OtherName3fooEv.resolver
+// CHECK: @_ZN3Foo3barEv = weak_odr ifunc i32 (), ptr @_ZN3Foo3barEv.resolver
 //.
-// CHECK-LABEL: define dso_local noundef i32 @_ZN4Name3fooEv.default(
-// CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
-// CHECK-NEXT:  [[ENTRY:.*:]]
-// CHECK-NEXT:    ret i32 0
-//
-//
 // CHECK-LABEL: define dso_local noundef i32 @_ZN4Name3fooEv._Msve(
-// CHECK-SAME: ) #[[ATTR1:[0-9]+]] {
+// CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
 // CHECK-NEXT:  [[ENTRY:.*:]]
 // CHECK-NEXT:    ret i32 1
 //
 //
 // CHECK-LABEL: define dso_local noundef i32 @_Z3barv(
-// CHECK-SAME: ) #[[ATTR0]] {
+// CHECK-SAME: ) #[[ATTR1:[0-9]+]] {
 // CHECK-NEXT:  [[ENTRY:.*:]]
 // CHECK-NEXT:    [[CALL:%.*]] = call noundef i32 @_ZN4Name3fooEv()
 // CHECK-NEXT:    ret i32 [[CALL]]
@@ -56,13 +57,13 @@ int baz() { return OtherName::foo(); }
 //
 //
 // CHECK-LABEL: define dso_local noundef i32 @_ZN9OtherName3fooEv._Msve(
-// CHECK-SAME: ) #[[ATTR1]] {
+// CHECK-SAME: ) #[[ATTR0]] {
 // CHECK-NEXT:  [[ENTRY:.*:]]
 // CHECK-NEXT:    ret i32 2
 //
 //
 // CHECK-LABEL: define dso_local noundef i32 @_Z3bazv(
-// CHECK-SAME: ) #[[ATTR0]] {
+// CHECK-SAME: ) #[[ATTR1]] {
 // CHECK-NEXT:  [[ENTRY:.*:]]
 // CHECK-NEXT:    [[CALL:%.*]] = call noundef i32 @_ZN9OtherName3fooEv()
 // CHECK-NEXT:    ret i32 [[CALL]]
@@ -81,10 +82,43 @@ int baz() { return OtherName::foo(); }
 // CHECK:       [[RESOLVER_ELSE]]:
 // CHECK-NEXT:    ret ptr @_ZN9OtherName3fooEv.default
 //
+//
+// CHECK-LABEL: define dso_local noundef i32 @_ZN3Foo3barEv.default(
+// CHECK-SAME: ) #[[ATTR1]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    ret i32 0
+//
+//
+// CHECK-LABEL: define dso_local noundef i32 @_ZN3Foo3barEv._Mmops(
+// CHECK-SAME: ) #[[ATTR2:[0-9]+]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    ret i32 1
+//
+//
+// CHECK-LABEL: define dso_local noundef i32 @_ZN4Name3fooEv.default(
+// CHECK-SAME: ) #[[ATTR1]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    ret i32 0
+//
+//
+// CHECK-LABEL: define weak_odr ptr @_ZN3Foo3barEv.resolver() comdat {
+// CHECK-NEXT:  [[RESOLVER_ENTRY:.*:]]
+// CHECK-NEXT:    call void @__init_cpu_features_resolver()
+// CHECK-NEXT:    [[TMP0:%.*]] = load i64, ptr @__aarch64_cpu_features, align 8
+// CHECK-NEXT:    [[TMP1:%.*]] = and i64 [[TMP0]], 576460752303423488
+// CHECK-NEXT:    [[TMP2:%.*]] = icmp eq i64 [[TMP1]], 576460752303423488
+// CHECK-NEXT:    [[TMP3:%.*]] = and i1 true, [[TMP2]]
+// CHECK-NEXT:    br i1 [[TMP3]], label %[[RESOLVER_RETURN:.*]], label %[[RESOLVER_ELSE:.*]]
+// CHECK:       [[RESOLVER_RETURN]]:
+// CHECK-NEXT:    ret ptr @_ZN3Foo3barEv._Mmops
+// CHECK:       [[RESOLVER_ELSE]]:
+// CHECK-NEXT:    ret ptr @_ZN3Foo3barEv.default
+//
 //.
-// CHECK: attributes #[[ATTR0]] = { mustprogress noinline nounwind optnone "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
-// CHECK: attributes #[[ATTR1]] = { mustprogress noinline nounwind optnone "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-features"="+fp-armv8,+fullfp16,+neon,+sve" }
-// CHECK: attributes #[[ATTR2:[0-9]+]] = { "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
+// CHECK: attributes #[[ATTR0]] = { mustprogress noinline nounwind optnone "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-features"="+fp-armv8,+fullfp16,+neon,+sve" }
+// CHECK: attributes #[[ATTR1]] = { mustprogress noinline nounwind optnone "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
+// CHECK: attributes #[[ATTR2]] = { mustprogress noinline nounwind optnone "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-features"="+mops" }
+// CHECK: attributes #[[ATTR3:[0-9]+]] = { "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
 //.
 // CHECK: [[META0:![0-9]+]] = !{i32 1, !"wchar_size", i32 4}
 // CHECK: [[META1:![0-9]+]] = !{!"{{.*}}clang version {{.*}}"}
diff --git a/clang/test/Sema/attr-target-version.c b/clang/test/Sema/attr-target-version.c
index cd5be45..88a927a 100644
--- a/clang/test/Sema/attr-target-version.c
+++ b/clang/test/Sema/attr-target-version.c
@@ -104,6 +104,11 @@ int __attribute__((aarch64_vector_pcs, target_version("sha3"))) combine(void) {
 
 int __attribute__((target_version("fp+aes+pmull+rcpc"))) unspec_args() { return -1; }
 // expected-error@-1 {{multiversioned function must have a prototype}}
-// expected-error@+1 {{multiversioned function must have a prototype}}
 int __attribute__((target_version("default"))) unspec_args() { return 0; }
 int cargs() { return unspec_args(); }
+
+int unspec_args_implicit_default_first();
+// expected-error@-1 {{multiversioned function must have a prototype}}
+// expected-note@+1 {{function multiversioning caused by this declaration}}
+int __attribute__((target_version("aes"))) unspec_args_implicit_default_first() { return -1; }
+int __attribute__((target_version("default"))) unspec_args_implicit_default_first() { return 0; }