Auto merge of #38302 - Mark-Simulacrum:trans-cleanup, r=eddyb

Cleanup old trans

This is a cleanup of old trans, with the following main points:
 - Remove the `build.rs` API (prefer using `Builder` directly, which is now passed where needed through `BlockAndBuilder`).
 - Remove `Block` (inlining it into `BlockAndBuilder`)
 - Remove `Callee::call`, primarily through inlining and simplification of code.
 - Thinned `FunctionContext`:
   - `mir`, `debug_scopes`, `scopes`, and `fn_ty` are moved to `MirContext`.
   - `param_env` is moved to `SharedCrateContext` and renamed to `empty_param_env`.
   - `llretslotptr` is removed, replaced with more careful management of the return values in calls.
   - `landingpad_alloca` is inlined into cleanup.
   - `param_substs` are moved to `MirContext`.
   - `span` is removed, it was never set to anything but `None`.
   - `block_arena` and `lpad_arena` are removed, since neither was necessary (landing pads and block are quite small, and neither needs arena allocation).
 - Fixed `drop_in_place` not running other destructors in the same function.

Fixes #35566 (thanks to @est31 for confirming).

src/liballoc/heap.rs

@@ -127,6 +127,7 @@ pub fn usable_size(size: usize, align: usize) -> usize {
 pub const EMPTY: *mut () = 0x1 as *mut ();
 
 /// The allocator for unique pointers.
+// This function must not unwind. If it does, MIR trans will fail.
 #[cfg(not(test))]
 #[lang = "exchange_malloc"]
 #[inline]

src/librustc_llvm/ffi.rs

@@ -710,6 +710,7 @@ extern "C" {
 
     // Operations on instructions
     pub fn LLVMGetInstructionParent(Inst: ValueRef) -> BasicBlockRef;
+    pub fn LLVMGetFirstBasicBlock(Fn: ValueRef) -> BasicBlockRef;
     pub fn LLVMGetFirstInstruction(BB: BasicBlockRef) -> ValueRef;
     pub fn LLVMInstructionEraseFromParent(Inst: ValueRef);
 

src/librustc_trans/abi.rs

@@ -10,7 +10,6 @@
 
 use llvm::{self, ValueRef, Integer, Pointer, Float, Double, Struct, Array, Vector, AttributePlace};
 use base;
-use build::AllocaFcx;
 use common::{type_is_fat_ptr, BlockAndBuilder, C_uint};
 use context::CrateContext;
 use cabi_x86;
@@ -99,21 +98,11 @@ impl ArgAttributes {
         self
     }
 
-    pub fn unset(&mut self, attr: ArgAttribute) -> &mut Self {
-        self.regular = self.regular - attr;
-        self
-    }
-
     pub fn set_dereferenceable(&mut self, bytes: u64) -> &mut Self {
         self.dereferenceable_bytes = bytes;
         self
     }
 
-    pub fn unset_dereferenceable(&mut self) -> &mut Self {
-        self.dereferenceable_bytes = 0;
-        self
-    }
-
     pub fn apply_llfn(&self, idx: AttributePlace, llfn: ValueRef) {
         unsafe {
             self.regular.for_each_kind(|attr| attr.apply_llfn(idx, llfn));
@@ -246,7 +235,7 @@ impl ArgType {
         if self.is_ignore() {
             return;
         }
-        let ccx = bcx.ccx();
+        let ccx = bcx.ccx;
         if self.is_indirect() {
             let llsz = llsize_of(ccx, self.ty);
             let llalign = llalign_of_min(ccx, self.ty);
@@ -278,7 +267,7 @@ impl ArgType {
                 //   bitcasting to the struct type yields invalid cast errors.
 
                 // We instead thus allocate some scratch space...
-                let llscratch = AllocaFcx(bcx.fcx(), ty, "abi_cast");
+                let llscratch = bcx.fcx().alloca(ty, "abi_cast");
                 base::Lifetime::Start.call(bcx, llscratch);
 
                 // ...where we first store the value...
@@ -431,7 +420,7 @@ impl FnType {
         let ret_ty = sig.output();
         let mut ret = arg_of(ret_ty, true);
 
-        if !type_is_fat_ptr(ccx.tcx(), ret_ty) {
+        if !type_is_fat_ptr(ccx, ret_ty) {
             // The `noalias` attribute on the return value is useful to a
             // function ptr caller.
             if let ty::TyBox(_) = ret_ty.sty {
@@ -496,7 +485,7 @@ impl FnType {
         for ty in inputs.iter().chain(extra_args.iter()) {
             let mut arg = arg_of(ty, false);
 
-            if type_is_fat_ptr(ccx.tcx(), ty) {
+            if type_is_fat_ptr(ccx, ty) {
                 let original_tys = arg.original_ty.field_types();
                 let sizing_tys = arg.ty.field_types();
                 assert_eq!((original_tys.len(), sizing_tys.len()), (2, 2));
@@ -569,7 +558,7 @@ impl FnType {
             };
             // Fat pointers are returned by-value.
             if !self.ret.is_ignore() {
-                if !type_is_fat_ptr(ccx.tcx(), sig.output()) {
+                if !type_is_fat_ptr(ccx, sig.output()) {
                     fixup(&mut self.ret);
                 }
             }