Rollup merge of #141569 - workingjubilee:canonicalize-abi, r=bjorn3

Replace ad-hoc ABI "adjustments" with an `AbiMap` to `CanonAbi`

Our `conv_from_spec_abi`, `adjust_abi`, and `is_abi_supported` combine to give us a very confusing way of reasoning about what _actual_ calling convention we want to lower our code to and whether we want to compile the resulting code at all. Instead of leaving this code as a miniature adventure game in which someone tries to combine stateful mutations into a Rube Goldberg machine that will let them escape the maze and arrive at the promised land of codegen, we let `AbiMap` devour this complexity. Once you have an `AbiMap`, you can answer which `ExternAbi`s will lower to what `CanonAbi`s (and whether they will lower at all).

Removed:
- `conv_from_spec_abi` replaced by `AbiMap::canonize_abi`
- `adjust_abi` replaced by same
- `Conv::PreserveAll` as unused
- `Conv::Cold` as unused
- `enum Conv` replaced by `enum CanonAbi`

target-spec.json changes:
- If you have a target-spec.json then now your "entry-abi" key will be specified in terms of one of the `"{abi}"` strings Rust recognizes, e.g.
```json
    "entry-abi": "C",
    "entry-abi": "win64",
    "entry-abi": "aapcs",
```

1 files changed, 4 insertions, 4 deletions

diff --git a/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs b/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs
index cfeaee07776..5478e54a606 100644
--- a/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs
+++ b/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs
@@ -1,6 +1,6 @@
 //! This module ensures that if a function's ABI requires a particular target feature,
 //! that target feature is enabled both on the callee and all callers.
-use rustc_abi::{BackendRepr, RegKind};
+use rustc_abi::{BackendRepr, CanonAbi, RegKind, X86Call};
 use rustc_hir::{CRATE_HIR_ID, HirId};
 use rustc_middle::mir::{self, Location, traversal};
 use rustc_middle::ty::layout::LayoutCx;
@@ -8,7 +8,7 @@ use rustc_middle::ty::{self, Instance, InstanceKind, Ty, TyCtxt, TypingEnv};
 use rustc_session::lint::builtin::WASM_C_ABI;
 use rustc_span::def_id::DefId;
 use rustc_span::{DUMMY_SP, Span, Symbol, sym};
-use rustc_target::callconv::{ArgAbi, Conv, FnAbi, PassMode};
+use rustc_target::callconv::{ArgAbi, FnAbi, PassMode};
 use rustc_target::spec::{HasWasmCAbiOpt, WasmCAbi};
 
 use crate::errors;
@@ -72,7 +72,7 @@ fn do_check_simd_vector_abi<'tcx>(
         }
     }
     // The `vectorcall` ABI is special in that it requires SSE2 no matter which types are being passed.
-    if abi.conv == Conv::X86VectorCall && !have_feature(sym::sse2) {
+    if abi.conv == CanonAbi::X86(X86Call::Vectorcall) && !have_feature(sym::sse2) {
         let (span, _hir_id) = loc();
         tcx.dcx().emit_err(errors::AbiRequiredTargetFeature {
             span,
@@ -128,7 +128,7 @@ fn do_check_wasm_abi<'tcx>(
     if !(tcx.sess.target.arch == "wasm32"
         && tcx.sess.target.os == "unknown"
         && tcx.wasm_c_abi_opt() == WasmCAbi::Legacy { with_lint: true }
-        && abi.conv == Conv::C)
+        && abi.conv == CanonAbi::C)
     {
         return;
     }