added typetree support for memcpy

Author: KMJ-007

compiler/rustc_codegen_llvm/src/abi.rs

@@ -244,6 +244,7 @@ impl<'ll, 'tcx> ArgAbiExt<'ll, 'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
                     scratch_align,
                     bx.const_usize(copy_bytes),
                     MemFlags::empty(),
+                    None,
                 );
                 bx.lifetime_end(llscratch, scratch_size);
             }

compiler/rustc_codegen_llvm/src/builder.rs

@@ -2,6 +2,7 @@ use std::borrow::{Borrow, Cow};
 use std::ops::Deref;
 use std::{iter, ptr};
 
+use rustc_ast::expand::typetree::FncTree;
 pub(crate) mod autodiff;
 pub(crate) mod gpu_offload;
 
@@ -1118,11 +1119,12 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         src_align: Align,
         size: &'ll Value,
         flags: MemFlags,
+        tt: Option<FncTree>,
     ) {
         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);
-        unsafe {
+        let memcpy = unsafe {
             llvm::LLVMRustBuildMemCpy(
                 self.llbuilder,
                 dst,
@@ -1131,7 +1133,16 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 src_align.bytes() as c_uint,
                 size,
                 is_volatile,
-            );
+            )
+        };
+
+        // TypeTree metadata for memcpy is especially important: when Enzyme encounters
+        // a memcpy during autodiff, it needs to know the structure of the data being
+        // copied to properly track derivatives. For example, copying an array of floats
+        // vs. copying a struct with mixed types requires different derivative handling.
+        // The TypeTree tells Enzyme exactly what memory layout to expect.
+        if let Some(tt) = tt {
+            crate::typetree::add_tt(self.cx().llmod, self.cx().llcx, memcpy, tt);
         }
     }
 

compiler/rustc_codegen_llvm/src/va_arg.rs

@@ -735,6 +735,7 @@ fn copy_to_temporary_if_more_aligned<'ll, 'tcx>(
             src_align,
             bx.const_u32(layout.layout.size().bytes() as u32),
             MemFlags::empty(),
+            None,
         );
         tmp
     } else {

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -1623,6 +1623,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     align,
                     bx.const_usize(copy_bytes),
                     MemFlags::empty(),
+                    None,
                 );
                 // ...and then load it with the ABI type.
                 llval = load_cast(bx, cast, llscratch, scratch_align);

compiler/rustc_codegen_ssa/src/mir/intrinsic.rs

@@ -30,7 +30,7 @@ fn copy_intrinsic<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     if allow_overlap {
         bx.memmove(dst, align, src, align, size, flags);
     } else {
-        bx.memcpy(dst, align, src, align, size, flags);
+        bx.memcpy(dst, align, src, align, size, flags, None);
     }
 }
 

compiler/rustc_codegen_ssa/src/mir/statement.rs

@@ -90,7 +90,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 let align = pointee_layout.align;
                 let dst = dst_val.immediate();
                 let src = src_val.immediate();
-                bx.memcpy(dst, align, src, align, bytes, crate::MemFlags::empty());
+                bx.memcpy(dst, align, src, align, bytes, crate::MemFlags::empty(), None);
             }
             mir::StatementKind::FakeRead(..)
             | mir::StatementKind::Retag { .. }

compiler/rustc_codegen_ssa/src/traits/builder.rs

@@ -424,6 +424,7 @@ pub trait BuilderMethods<'a, 'tcx>:
         src_align: Align,
         size: Self::Value,
         flags: MemFlags,
+        tt: Option<rustc_ast::expand::typetree::FncTree>,
     );
     fn memmove(
         &mut self,
@@ -480,7 +481,7 @@ pub trait BuilderMethods<'a, 'tcx>:
             temp.val.store_with_flags(self, dst.with_type(layout), flags);
         } else if !layout.is_zst() {
             let bytes = self.const_usize(layout.size.bytes());
-            self.memcpy(dst.llval, dst.align, src.llval, src.align, bytes, flags);
+            self.memcpy(dst.llval, dst.align, src.llval, src.align, bytes, flags, None);
         }
     }
 

compiler/rustc_middle/src/ty/mod.rs

@@ -2286,7 +2286,7 @@ pub fn typetree_from_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> TypeTree {
         let child = typetree_from_ty(tcx, inner_ty);
         return TypeTree(vec![Type {
             offset: -1,
-            size: 8, // TODO(KMJ-007): Get actual pointer size from target
+            size: tcx.data_layout.pointer_size().bytes_usize(),
             kind: Kind::Pointer,
             child,
         }]);

tests/codegen-llvm/autodiff/typetree.rs

@@ -30,4 +30,4 @@ fn main() {
     let output_ = d_simple(&x, &mut df_dx, 1.0);
     assert_eq!(output, output_);
     assert_eq!(2.0, df_dx);
-}
+}

tests/run-make/autodiff/type-trees/memcpy-typetree/memcpy-ir.check

@@ -0,0 +1,8 @@
+; Check that enzyme_type attributes are present in the LLVM IR function definition
+; This verifies our TypeTree system correctly attaches metadata for Enzyme
+
+CHECK: define{{.*}}"enzyme_type"="{[]:Float@double}"{{.*}}@test_memcpy({{.*}}"enzyme_type"="{[]:Pointer}"
+
+; Check that llvm.memcpy exists (either call or declare)
+CHECK: {{(call|declare).*}}@llvm.memcpy
+