Prepare struct_gep for opaque pointers

Imlement struct_gep using LLVMBuildStructGEP2 which takes an explicit
type argument instead of deriving it from a pointer type.

Author: tmiasko

compiler/rustc_codegen_llvm/src/builder.rs

@@ -497,9 +497,10 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
             OperandValue::Immediate(self.to_immediate(llval, place.layout))
         } else if let abi::Abi::ScalarPair(ref a, ref b) = place.layout.abi {
             let b_offset = a.value.size(self).align_to(b.value.align(self).abi);
+            let pair_ty = place.layout.llvm_type(self);
 
             let mut load = |i, scalar: &abi::Scalar, align| {
-                let llptr = self.struct_gep(place.llval, i as u64);
+                let llptr = self.struct_gep(pair_ty, place.llval, i as u64);
                 let llty = place.layout.scalar_pair_element_llvm_type(self, i, false);
                 let load = self.load(llty, llptr, align);
                 scalar_load_metadata(self, load, scalar);
@@ -663,9 +664,9 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         }
     }
 
-    fn struct_gep(&mut self, ptr: &'ll Value, idx: u64) -> &'ll Value {
+    fn struct_gep(&mut self, ty: &'ll Type, ptr: &'ll Value, idx: u64) -> &'ll Value {
         assert_eq!(idx as c_uint as u64, idx);
-        unsafe { llvm::LLVMBuildStructGEP(self.llbuilder, ptr, idx as c_uint, UNNAMED) }
+        unsafe { llvm::LLVMBuildStructGEP2(self.llbuilder, ty, ptr, idx as c_uint, UNNAMED) }
     }
 
     /* Casts */

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1408,8 +1408,9 @@ extern "C" {
         NumIndices: c_uint,
         Name: *const c_char,
     ) -> &'a Value;
-    pub fn LLVMBuildStructGEP(
+    pub fn LLVMBuildStructGEP2(
         B: &Builder<'a>,
+        Ty: &'a Type,
         Pointer: &'a Value,
         Idx: c_uint,
         Name: *const c_char,

compiler/rustc_codegen_llvm/src/va_arg.rs

@@ -98,6 +98,7 @@ fn emit_aapcs_va_arg(
     // Implementation of the AAPCS64 calling convention for va_args see
     // https://github.com/ARM-software/abi-aa/blob/master/aapcs64/aapcs64.rst
     let va_list_addr = list.immediate();
+    let va_list_ty = list.deref(bx.cx).layout.llvm_type(bx);
     let layout = bx.cx.layout_of(target_ty);
 
     let mut maybe_reg = bx.build_sibling_block("va_arg.maybe_reg");
@@ -109,11 +110,11 @@ fn emit_aapcs_va_arg(
 
     let gr_type = target_ty.is_any_ptr() || target_ty.is_integral();
     let (reg_off, reg_top_index, slot_size) = if gr_type {
-        let gr_offs = bx.struct_gep(va_list_addr, 7);
+        let gr_offs = bx.struct_gep(va_list_ty, va_list_addr, 7);
         let nreg = (layout.size.bytes() + 7) / 8;
         (gr_offs, 3, nreg * 8)
     } else {
-        let vr_off = bx.struct_gep(va_list_addr, 9);
+        let vr_off = bx.struct_gep(va_list_ty, va_list_addr, 9);
         let nreg = (layout.size.bytes() + 15) / 16;
         (vr_off, 5, nreg * 16)
     };
@@ -141,7 +142,7 @@ fn emit_aapcs_va_arg(
     maybe_reg.cond_br(use_stack, &on_stack.llbb(), &in_reg.llbb());
 
     let top_type = bx.type_i8p();
-    let top = in_reg.struct_gep(va_list_addr, reg_top_index);
+    let top = in_reg.struct_gep(va_list_ty, va_list_addr, reg_top_index);
     let top = in_reg.load(top_type, top, bx.tcx().data_layout.pointer_align.abi);
 
     // reg_value = *(@top + reg_off_v);

compiler/rustc_codegen_ssa/src/mir/operand.rs

@@ -311,14 +311,15 @@ impl<'a, 'tcx, V: CodegenObject> OperandValue<V> {
                     Abi::ScalarPair(ref a, ref b) => (a, b),
                     _ => bug!("store_with_flags: invalid ScalarPair layout: {:#?}", dest.layout),
                 };
+                let ty = bx.backend_type(dest.layout);
                 let b_offset = a_scalar.value.size(bx).align_to(b_scalar.value.align(bx).abi);
 
-                let llptr = bx.struct_gep(dest.llval, 0);
+                let llptr = bx.struct_gep(ty, dest.llval, 0);
                 let val = bx.from_immediate(a);
                 let align = dest.align;
                 bx.store_with_flags(val, llptr, align, flags);
 
-                let llptr = bx.struct_gep(dest.llval, 1);
+                let llptr = bx.struct_gep(ty, dest.llval, 1);
                 let val = bx.from_immediate(b);
                 let align = dest.align.restrict_for_offset(b_offset);
                 bx.store_with_flags(val, llptr, align, flags);

compiler/rustc_codegen_ssa/src/mir/place.rs

@@ -103,7 +103,8 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
                     if offset == a.value.size(bx.cx()).align_to(b.value.align(bx.cx()).abi) =>
                 {
                     // Offset matches second field.
-                    bx.struct_gep(self.llval, 1)
+                    let ty = bx.backend_type(self.layout);
+                    bx.struct_gep(ty, self.llval, 1)
                 }
                 Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. } if field.is_zst() => {
                     // ZST fields are not included in Scalar, ScalarPair, and Vector layouts, so manually offset the pointer.
@@ -119,7 +120,10 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
                         self.layout
                     );
                 }
-                _ => bx.struct_gep(self.llval, bx.cx().backend_field_index(self.layout, ix)),
+                _ => {
+                    let ty = bx.backend_type(self.layout);
+                    bx.struct_gep(ty, self.llval, bx.cx().backend_field_index(self.layout, ix))
+                }
             };
             PlaceRef {
                 // HACK(eddyb): have to bitcast pointers until LLVM removes pointee types.

compiler/rustc_codegen_ssa/src/traits/builder.rs

@@ -178,7 +178,7 @@ pub trait BuilderMethods<'a, 'tcx>:
 
     fn gep(&mut self, ptr: Self::Value, indices: &[Self::Value]) -> Self::Value;
     fn inbounds_gep(&mut self, ptr: Self::Value, indices: &[Self::Value]) -> Self::Value;
-    fn struct_gep(&mut self, ptr: Self::Value, idx: u64) -> Self::Value;
+    fn struct_gep(&mut self, ty: Self::Type, ptr: Self::Value, idx: u64) -> Self::Value;
 
     fn trunc(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
     fn sext(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;