cg_ssa, cg_llvm: remove unnecessary pointercast/bitcast-of-ptr

Author: erikdesjardins

compiler/rustc_codegen_llvm/src/abi.rs

@@ -226,9 +226,7 @@ impl<'ll, 'tcx> ArgAbiExt<'ll, 'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
             // uses it for i16 -> {i8, i8}, but not for i24 -> {i8, i8, i8}.
             let can_store_through_cast_ptr = false;
             if can_store_through_cast_ptr {
-                let cast_ptr_llty = bx.type_ptr();
-                let cast_dst = bx.pointercast(dst.llval, cast_ptr_llty);
-                bx.store(val, cast_dst, self.layout.align.abi);
+                bx.store(val, dst.llval, self.layout.align.abi);
             } else {
                 // The actual return type is a struct, but the ABI
                 // adaptation code has cast it into some scalar type.  The

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -4,7 +4,6 @@ use crate::back::profiling::{
 };
 use crate::base;
 use crate::common;
-use crate::consts;
 use crate::llvm::{self, DiagnosticInfo, PassManager};
 use crate::llvm_util;
 use crate::type_::Type;
@@ -948,7 +947,7 @@ fn create_msvc_imps(
 
         for (imp_name, val) in globals {
             let imp = llvm::LLVMAddGlobal(llmod, ptr_ty, imp_name.as_ptr().cast());
-            llvm::LLVMSetInitializer(imp, consts::ptrcast(val, ptr_ty));
+            llvm::LLVMSetInitializer(imp, val);
             llvm::LLVMRustSetLinkage(imp, llvm::Linkage::ExternalLinkage);
         }
     }

compiler/rustc_codegen_llvm/src/base.rs

@@ -123,8 +123,7 @@ pub fn compile_codegen_unit(tcx: TyCtxt<'_>, cgu_name: Symbol) -> (ModuleCodegen
             // happen after the llvm.used variables are created.
             for &(old_g, new_g) in cx.statics_to_rauw().borrow().iter() {
                 unsafe {
-                    let bitcast = llvm::LLVMConstPointerCast(new_g, cx.val_ty(old_g));
-                    llvm::LLVMReplaceAllUsesWith(old_g, bitcast);
+                    llvm::LLVMReplaceAllUsesWith(old_g, new_g);
                     llvm::LLVMDeleteGlobal(old_g);
                 }
             }

compiler/rustc_codegen_llvm/src/builder.rs

@@ -854,8 +854,6 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         assert!(!flags.contains(MemFlags::NONTEMPORAL), "non-temporal memcpy not supported");
         let size = self.intcast(size, self.type_isize(), false);
         let is_volatile = flags.contains(MemFlags::VOLATILE);
-        let dst = self.pointercast(dst, self.type_ptr());
-        let src = self.pointercast(src, self.type_ptr());
         unsafe {
             llvm::LLVMRustBuildMemCpy(
                 self.llbuilder,
@@ -881,8 +879,6 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         assert!(!flags.contains(MemFlags::NONTEMPORAL), "non-temporal memmove not supported");
         let size = self.intcast(size, self.type_isize(), false);
         let is_volatile = flags.contains(MemFlags::VOLATILE);
-        let dst = self.pointercast(dst, self.type_ptr());
-        let src = self.pointercast(src, self.type_ptr());
         unsafe {
             llvm::LLVMRustBuildMemMove(
                 self.llbuilder,
@@ -905,7 +901,6 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         flags: MemFlags,
     ) {
         let is_volatile = flags.contains(MemFlags::VOLATILE);
-        let ptr = self.pointercast(ptr, self.type_ptr());
         unsafe {
             llvm::LLVMRustBuildMemSet(
                 self.llbuilder,
@@ -1342,20 +1337,10 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
 
     fn check_store(&mut self, ptr: &'ll Value) -> &'ll Value {
         let dest_ptr_ty = self.cx.val_ty(ptr);
-        let stored_ptr_ty = self.cx.type_ptr();
 
         assert_eq!(self.cx.type_kind(dest_ptr_ty), TypeKind::Pointer);
 
-        if dest_ptr_ty == stored_ptr_ty {
-            ptr
-        } else {
-            debug!(
-                "type mismatch in store. \
-                    Expected {:?}, got {:?}; inserting bitcast",
-                dest_ptr_ty, stored_ptr_ty
-            );
-            self.bitcast(ptr, stored_ptr_ty)
-        }
+        ptr
     }
 
     fn check_call<'b>(
@@ -1420,7 +1405,6 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
             return;
         }
 
-        let ptr = self.pointercast(ptr, self.cx.type_ptr());
         self.call_intrinsic(intrinsic, &[self.cx.const_u64(size), ptr]);
     }
 

compiler/rustc_codegen_llvm/src/callee.rs

@@ -4,13 +4,11 @@
 //! and methods are represented as just a fn ptr and not a full
 //! closure.
 
-use crate::abi::FnAbiLlvmExt;
 use crate::attributes;
 use crate::common;
 use crate::context::CodegenCx;
 use crate::llvm;
 use crate::value::Value;
-use rustc_codegen_ssa::traits::*;
 
 use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt};
 use rustc_middle::ty::{self, Instance, TypeVisitable};
@@ -45,39 +43,7 @@ pub fn get_fn<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>) ->
     let fn_abi = cx.fn_abi_of_instance(instance, ty::List::empty());
 
     let llfn = if let Some(llfn) = cx.get_declared_value(sym) {
-        // Create a fn pointer with the new signature.
-        let llptrty = fn_abi.ptr_to_llvm_type(cx);
-
-        // This is subtle and surprising, but sometimes we have to bitcast
-        // the resulting fn pointer.  The reason has to do with external
-        // functions.  If you have two crates that both bind the same C
-        // library, they may not use precisely the same types: for
-        // example, they will probably each declare their own structs,
-        // which are distinct types from LLVM's point of view (nominal
-        // types).
-        //
-        // Now, if those two crates are linked into an application, and
-        // they contain inlined code, you can wind up with a situation
-        // where both of those functions wind up being loaded into this
-        // application simultaneously. In that case, the same function
-        // (from LLVM's point of view) requires two types. But of course
-        // LLVM won't allow one function to have two types.
-        //
-        // What we currently do, therefore, is declare the function with
-        // one of the two types (whichever happens to come first) and then
-        // bitcast as needed when the function is referenced to make sure
-        // it has the type we expect.
-        //
-        // This can occur on either a crate-local or crate-external
-        // reference. It also occurs when testing libcore and in some
-        // other weird situations. Annoying.
-        if cx.val_ty(llfn) != llptrty {
-            debug!("get_fn: casting {:?} to {:?}", llfn, llptrty);
-            cx.const_ptrcast(llfn, llptrty)
-        } else {
-            debug!("get_fn: not casting pointer!");
-            llfn
-        }
+        llfn
     } else {
         let instance_def_id = instance.def_id();
         let llfn = if tcx.sess.target.arch == "x86" &&

compiler/rustc_codegen_llvm/src/common.rs

@@ -1,6 +1,6 @@
 //! Code that is useful in various codegen modules.
 
-use crate::consts::{self, const_alloc_to_llvm};
+use crate::consts::const_alloc_to_llvm;
 pub use crate::context::CodegenCx;
 use crate::llvm::{self, BasicBlock, Bool, ConstantInt, False, OperandBundleDef, True};
 use crate::type_::Type;
@@ -202,8 +202,7 @@ impl<'ll, 'tcx> ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             })
             .1;
         let len = s.len();
-        let cs = consts::ptrcast(str_global, self.type_ptr());
-        (cs, self.const_usize(len as u64))
+        (str_global, self.const_usize(len as u64))
     }
 
     fn const_struct(&self, elts: &[&'ll Value], packed: bool) -> &'ll Value {
@@ -312,19 +311,15 @@ impl<'ll, 'tcx> ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             let llval = unsafe {
                 llvm::LLVMRustConstInBoundsGEP2(
                     self.type_i8(),
-                    self.const_bitcast(base_addr, self.type_ptr()),
+                    base_addr,
                     &self.const_usize(offset.bytes()),
                     1,
                 )
             };
-            self.const_bitcast(llval, llty)
+            llval
         };
         PlaceRef::new_sized(llval, layout)
     }
-
-    fn const_ptrcast(&self, val: &'ll Value, ty: &'ll Type) -> &'ll Value {
-        consts::ptrcast(val, ty)
-    }
 }
 
 /// Get the [LLVM type][Type] of a [`Value`].

compiler/rustc_codegen_llvm/src/consts.rs

@@ -209,10 +209,6 @@ fn check_and_apply_linkage<'ll, 'tcx>(
     }
 }
 
-pub fn ptrcast<'ll>(val: &'ll Value, ty: &'ll Type) -> &'ll Value {
-    unsafe { llvm::LLVMConstPointerCast(val, ty) }
-}
-
 impl<'ll> CodegenCx<'ll, '_> {
     pub(crate) fn const_bitcast(&self, val: &'ll Value, ty: &'ll Type) -> &'ll Value {
         unsafe { llvm::LLVMConstBitCast(val, ty) }
@@ -572,14 +568,12 @@ impl<'ll> StaticMethods for CodegenCx<'ll, '_> {
 
     /// Add a global value to a list to be stored in the `llvm.used` variable, an array of ptr.
     fn add_used_global(&self, global: &'ll Value) {
-        let cast = unsafe { llvm::LLVMConstPointerCast(global, self.type_ptr()) };
-        self.used_statics.borrow_mut().push(cast);
+        self.used_statics.borrow_mut().push(global);
     }
 
     /// Add a global value to a list to be stored in the `llvm.compiler.used` variable,
     /// an array of ptr.
     fn add_compiler_used_global(&self, global: &'ll Value) {
-        let cast = unsafe { llvm::LLVMConstPointerCast(global, self.type_ptr()) };
-        self.compiler_used_statics.borrow_mut().push(cast);
+        self.compiler_used_statics.borrow_mut().push(global);
     }
 }

compiler/rustc_codegen_llvm/src/context.rs

@@ -59,17 +59,6 @@ pub struct CodegenCx<'ll, 'tcx> {
     /// Cache of constant strings,
     pub const_str_cache: RefCell<FxHashMap<String, &'ll Value>>,
 
-    /// Reverse-direction for const ptrs cast from globals.
-    ///
-    /// Key is a Value holding a `*T`,
-    /// Val is a Value holding a `*[T]`.
-    ///
-    /// Needed because LLVM loses pointer->pointee association
-    /// when we ptrcast, and we have to ptrcast during codegen
-    /// of a `[T]` const because we form a slice, a `(*T,usize)` pair, not
-    /// a pointer to an LLVM array type. Similar for trait objects.
-    pub const_unsized: RefCell<FxHashMap<&'ll Value, &'ll Value>>,
-
     /// Cache of emitted const globals (value -> global)
     pub const_globals: RefCell<FxHashMap<&'ll Value, &'ll Value>>,
 
@@ -435,7 +424,6 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
             instances: Default::default(),
             vtables: Default::default(),
             const_str_cache: Default::default(),
-            const_unsized: Default::default(),
             const_globals: Default::default(),
             statics_to_rauw: RefCell::new(Vec::new()),
             used_statics: RefCell::new(Vec::new()),
@@ -903,7 +891,6 @@ impl<'ll> CodegenCx<'ll, '_> {
                 self.declare_global("rust_eh_catch_typeinfo", ty)
             }
         };
-        let eh_catch_typeinfo = self.const_bitcast(eh_catch_typeinfo, self.type_ptr());
         self.eh_catch_typeinfo.set(Some(eh_catch_typeinfo));
         eh_catch_typeinfo
     }

compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs

@@ -18,8 +18,7 @@ use rustc_span::DebuggerVisualizerType;
 /// .debug_gdb_scripts global is referenced, so it isn't removed by the linker.
 pub fn insert_reference_to_gdb_debug_scripts_section_global(bx: &mut Builder<'_, '_, '_>) {
     if needs_gdb_debug_scripts_section(bx) {
-        let gdb_debug_scripts_section =
-            bx.const_bitcast(get_or_insert_gdb_debug_scripts_section_global(bx), bx.type_ptr());
+        let gdb_debug_scripts_section = get_or_insert_gdb_debug_scripts_section_global(bx);
         // Load just the first byte as that's all that's necessary to force
         // LLVM to keep around the reference to the global.
         let volative_load_instruction = bx.volatile_load(bx.type_i8(), gdb_debug_scripts_section);

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -165,7 +165,6 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                 let ptr = args[0].immediate();
                 let load = if let PassMode::Cast(ty, _) = &fn_abi.ret.mode {
                     let llty = ty.llvm_type(self);
-                    let ptr = self.pointercast(ptr, self.type_ptr());
                     self.volatile_load(llty, ptr)
                 } else {
                     self.volatile_load(self.layout_of(tp_ty).llvm_type(self), ptr)
@@ -319,18 +318,12 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                     self.const_bool(true)
                 } else if use_integer_compare {
                     let integer_ty = self.type_ix(layout.size().bits());
-                    let ptr_ty = self.type_ptr();
-                    let a_ptr = self.bitcast(a, ptr_ty);
-                    let a_val = self.load(integer_ty, a_ptr, layout.align().abi);
-                    let b_ptr = self.bitcast(b, ptr_ty);
-                    let b_val = self.load(integer_ty, b_ptr, layout.align().abi);
+                    let a_val = self.load(integer_ty, a, layout.align().abi);
+                    let b_val = self.load(integer_ty, b, layout.align().abi);
                     self.icmp(IntPredicate::IntEQ, a_val, b_val)
                 } else {
-                    let ptr_ty = self.type_ptr();
-                    let a_ptr = self.bitcast(a, ptr_ty);
-                    let b_ptr = self.bitcast(b, ptr_ty);
                     let n = self.const_usize(layout.size().bytes());
-                    let cmp = self.call_intrinsic("memcmp", &[a_ptr, b_ptr, n]);
+                    let cmp = self.call_intrinsic("memcmp", &[a, b, n]);
                     match self.cx.sess().target.arch.as_ref() {
                         "avr" | "msp430" => self.icmp(IntPredicate::IntEQ, cmp, self.const_i16(0)),
                         _ => self.icmp(IntPredicate::IntEQ, cmp, self.const_i32(0)),
@@ -386,9 +379,7 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
 
         if !fn_abi.ret.is_ignore() {
             if let PassMode::Cast(_, _) = &fn_abi.ret.mode {
-                let ptr_llty = self.type_ptr();
-                let ptr = self.pointercast(result.llval, ptr_llty);
-                self.store(llval, ptr, result.align);
+                self.store(llval, result.llval, result.align);
             } else {
                 OperandRef::from_immediate_or_packed_pair(self, llval, result.layout)
                     .val
@@ -412,9 +403,7 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
     fn type_test(&mut self, pointer: Self::Value, typeid: Self::Value) -> Self::Value {
         // Test the called operand using llvm.type.test intrinsic. The LowerTypeTests link-time
         // optimization pass replaces calls to this intrinsic with code to test type membership.
-        let ptr_ty = self.type_ptr();
-        let bitcast = self.bitcast(pointer, ptr_ty);
-        self.call_intrinsic("llvm.type.test", &[bitcast, typeid])
+        self.call_intrinsic("llvm.type.test", &[pointer, typeid])
     }
 
     fn type_checked_load(
@@ -748,7 +737,6 @@ fn codegen_emcc_try<'ll>(
         let catch_data_1 =
             bx.inbounds_gep(catch_data_type, catch_data, &[bx.const_usize(0), bx.const_usize(1)]);
         bx.store(is_rust_panic, catch_data_1, i8_align);
-        let catch_data = bx.bitcast(catch_data, bx.type_ptr());
 
         let catch_ty = bx.type_func(&[bx.type_ptr(), bx.type_ptr()], bx.type_void());
         bx.call(catch_ty, None, catch_func, &[data, catch_data], None);
@@ -897,8 +885,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
                 let place = PlaceRef::alloca(bx, args[0].layout);
                 args[0].val.store(bx, place);
                 let int_ty = bx.type_ix(expected_bytes * 8);
-                let ptr = bx.pointercast(place.llval, bx.cx.type_ptr());
-                bx.load(int_ty, ptr, Align::ONE)
+                bx.load(int_ty, place.llval, Align::ONE)
             }
             _ => return_error!(
                 "invalid bitmask `{}`, expected `u{}` or `[u8; {}]`",
@@ -1145,7 +1132,6 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
                 let ptr = bx.alloca(bx.type_ix(expected_bytes * 8), Align::ONE);
                 bx.store(ze, ptr, Align::ONE);
                 let array_ty = bx.type_array(bx.type_i8(), expected_bytes);
-                let ptr = bx.pointercast(ptr, bx.cx.type_ptr());
                 return Ok(bx.load(array_ty, ptr, Align::ONE));
             }
             _ => return_error!(
@@ -1763,11 +1749,7 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
             _ => return_error!("expected pointer, got `{}`", out_elem),
         }
 
-        if in_elem == out_elem {
-            return Ok(args[0].immediate());
-        } else {
-            return Ok(bx.pointercast(args[0].immediate(), llret_ty));
-        }
+        return Ok(args[0].immediate());
     }
 
     if name == sym::simd_expose_addr {