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Unify "needs thunk" logic. (#6277)

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Remove duplication between determining whether a parameter needs custom
thunk mapping and whether a function needs a thunk. Now a function needs
a thunk if any parameter or the return type does.

This fixes some inconsistencies; previously:
- We would not require a thunk when passing an `unsigned int`, but if we
  had a thunk we'd pass `unsigned int` indirectly.
- We would always require a thunk for an enum parameter, even though
  we'd actually pass it directly if its underlying type is a 32- or
  64-bit integer.
- We would require a thunk for a nullable pointer, even though
  we arrange for all pointer types to have the same ABI in Carbon and
  C++, including nullable pointers / Optional(T*).

This also causes us to use a thunk for rvalue reference return types,
which we used to miscompile.

Depends on #6276.
This commit is contained in:
Richard Smith
2025-10-27 22:49:29 +00:00
committed by GitHub
parent f022e91e45
commit a1a35c207e
7 changed files with 181 additions and 229 deletions
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toolchain/check/testdata/interop/cpp/function/pointer.carbon
Vendored
+9 -9
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@@ -663,8 +663,8 @@ fn F() {
// CHECK:STDOUT: %OptionalStorage.impl_witness.707: <witness> = impl_witness imports.%OptionalStorage.impl_witness_table.377, @ptr.as.OptionalStorage.impl(%S) [concrete]
// CHECK:STDOUT: %OptionalStorage.facet: %OptionalStorage.type = facet_value %ptr.5c7, (%OptionalStorage.impl_witness.707) [concrete]
// CHECK:STDOUT: %Optional.143: type = class_type @Optional, @Optional(%OptionalStorage.facet) [concrete]
// CHECK:STDOUT: %foo__carbon_thunk.type: type = fn_type @foo__carbon_thunk [concrete]
// CHECK:STDOUT: %foo__carbon_thunk: %foo__carbon_thunk.type = struct_value () [concrete]
// CHECK:STDOUT: %foo.type: type = fn_type @foo [concrete]
// CHECK:STDOUT: %foo: %foo.type = struct_value () [concrete]
// CHECK:STDOUT: %ImplicitAs.type.06b: type = facet_type <@ImplicitAs, @ImplicitAs(%Optional.143)> [concrete]
// CHECK:STDOUT: %ImplicitAs.Convert.type.e1b: type = fn_type @ImplicitAs.Convert, @ImplicitAs(%Optional.143) [concrete]
// CHECK:STDOUT: %T.binding.as_type.as.ImplicitAs.impl.Convert.type.6f7: type = fn_type @T.binding.as_type.as.ImplicitAs.impl.Convert.1, @T.binding.as_type.as.ImplicitAs.impl.3a5(%T.76d) [symbolic]
@@ -699,7 +699,7 @@ fn F() {
// CHECK:STDOUT: %Core.import_ref.6db = import_ref Core//prelude/types/optional, loc{{\d+_\d+}}, unloaded
// CHECK:STDOUT: %Core.import_ref.5a7 = import_ref Core//prelude/types/optional, loc{{\d+_\d+}}, unloaded
// CHECK:STDOUT: %OptionalStorage.impl_witness_table.377 = impl_witness_table (%Core.import_ref.8c0, %Core.import_ref.566, %Core.import_ref.637, %Core.import_ref.6db, %Core.import_ref.5a7), @ptr.as.OptionalStorage.impl [concrete]
// CHECK:STDOUT: %foo__carbon_thunk.decl: %foo__carbon_thunk.type = fn_decl @foo__carbon_thunk [concrete = constants.%foo__carbon_thunk] {
// CHECK:STDOUT: %foo.decl: %foo.type = fn_decl @foo [concrete = constants.%foo] {
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: } {
// CHECK:STDOUT: <elided>
@@ -743,7 +743,7 @@ fn F() {
// CHECK:STDOUT: %.loc9_11.2: init %Optional.143 = converted %addr.loc9_11.1, %T.binding.as_type.as.ImplicitAs.impl.Convert.call
// CHECK:STDOUT: %.loc9_11.3: ref %Optional.143 = temporary %.loc9_11.1, %.loc9_11.2
// CHECK:STDOUT: %.loc9_11.4: %Optional.143 = bind_value %.loc9_11.3
// CHECK:STDOUT: %foo__carbon_thunk.call: init %empty_tuple.type = call imports.%foo__carbon_thunk.decl(%.loc9_11.4)
// CHECK:STDOUT: %foo.call: init %empty_tuple.type = call imports.%foo.decl(%.loc9_11.4)
// CHECK:STDOUT: %DestroyT.binding.as_type.as.Destroy.impl.Op.bound.loc9: <bound method> = bound_method %.loc9_11.3, constants.%DestroyT.binding.as_type.as.Destroy.impl.Op.465
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: %bound_method.loc9_11.3: <bound method> = bound_method %.loc9_11.3, %DestroyT.binding.as_type.as.Destroy.impl.Op.specific_fn.1
@@ -925,8 +925,8 @@ fn F() {
// CHECK:STDOUT: %OptionalStorage.facet: %OptionalStorage.type = facet_value %ptr.5c7, (%OptionalStorage.impl_witness.707) [concrete]
// CHECK:STDOUT: %Optional.143: type = class_type @Optional, @Optional(%OptionalStorage.facet) [concrete]
// CHECK:STDOUT: %pattern_type.aa5: type = pattern_type %Optional.143 [concrete]
// CHECK:STDOUT: %Direct__carbon_thunk.type: type = fn_type @Direct__carbon_thunk [concrete]
// CHECK:STDOUT: %Direct__carbon_thunk: %Direct__carbon_thunk.type = struct_value () [concrete]
// CHECK:STDOUT: %Direct.type: type = fn_type @Direct [concrete]
// CHECK:STDOUT: %Direct: %Direct.type = struct_value () [concrete]
// CHECK:STDOUT: %ImplicitAs.type.cc7: type = generic_interface_type @ImplicitAs [concrete]
// CHECK:STDOUT: %ImplicitAs.generic: %ImplicitAs.type.cc7 = struct_value () [concrete]
// CHECK:STDOUT: %ImplicitAs.type.06b: type = facet_type <@ImplicitAs, @ImplicitAs(%Optional.143)> [concrete]
@@ -977,7 +977,7 @@ fn F() {
// CHECK:STDOUT: %Core.import_ref.6db = import_ref Core//prelude/types/optional, loc{{\d+_\d+}}, unloaded
// CHECK:STDOUT: %Core.import_ref.5a7 = import_ref Core//prelude/types/optional, loc{{\d+_\d+}}, unloaded
// CHECK:STDOUT: %OptionalStorage.impl_witness_table.377 = impl_witness_table (%Core.import_ref.8c0, %Core.import_ref.566, %Core.import_ref.637, %Core.import_ref.6db, %Core.import_ref.5a7), @ptr.as.OptionalStorage.impl [concrete]
// CHECK:STDOUT: %Direct__carbon_thunk.decl: %Direct__carbon_thunk.type = fn_decl @Direct__carbon_thunk [concrete = constants.%Direct__carbon_thunk] {
// CHECK:STDOUT: %Direct.decl: %Direct.type = fn_decl @Direct [concrete = constants.%Direct] {
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: } {
// CHECK:STDOUT: %OptionalStorage.facet.loc11_16.1: %OptionalStorage.type = facet_value constants.%ptr.5c7, (constants.%OptionalStorage.impl_witness.707) [concrete = constants.%OptionalStorage.facet]
@@ -1036,8 +1036,8 @@ fn F() {
// CHECK:STDOUT: %.loc11_14.2: init %Optional.143 = converted %addr.loc11_14.1, %T.binding.as_type.as.ImplicitAs.impl.Convert.call
// CHECK:STDOUT: %.loc11_14.3: ref %Optional.143 = temporary %.loc11_14.1, %.loc11_14.2
// CHECK:STDOUT: %.loc11_14.4: %Optional.143 = bind_value %.loc11_14.3
// CHECK:STDOUT: %Direct__carbon_thunk.call: init %Optional.143 = call imports.%Direct__carbon_thunk.decl(%.loc11_14.4) to %.loc11_16.1
// CHECK:STDOUT: %.loc11_16.2: ref %Optional.143 = temporary %.loc11_16.1, %Direct__carbon_thunk.call
// CHECK:STDOUT: %Direct.call: init %Optional.143 = call imports.%Direct.decl(%.loc11_14.4) to %.loc11_16.1
// CHECK:STDOUT: %.loc11_16.2: ref %Optional.143 = temporary %.loc11_16.1, %Direct.call
// CHECK:STDOUT: name_binding_decl {
// CHECK:STDOUT: %a.patt: %pattern_type.aa5 = value_binding_pattern a [concrete]
// CHECK:STDOUT: }