add and use generic get_const_int function

Author: ZuseZ4

compiler/rustc_codegen_llvm/src/builder/autodiff.rs

@@ -114,7 +114,7 @@ fn match_args_from_caller_to_enzyme<'ll>(
             let mul = unsafe {
                 llvm::LLVMBuildMul(
                     builder.llbuilder,
-                    cx.get_const_i64(elem_bytes_size),
+                    cx.get_const_int(cx.type_i64(), elem_bytes_size),
                     next_outer_arg,
                     UNNAMED,
                 )
@@ -385,7 +385,7 @@ fn generate_enzyme_call<'ll>(
         if attrs.width > 1 {
             let enzyme_width = cx.create_metadata("enzyme_width".to_string()).unwrap();
             args.push(cx.get_metadata_value(enzyme_width));
-            args.push(cx.get_const_i64(attrs.width as u64));
+            args.push(cx.get_const_int(cx.type_i64(), attrs.width as u64));
         }
 
         let has_sret = has_sret(outer_fn);

compiler/rustc_codegen_llvm/src/context.rs

@@ -678,11 +678,10 @@ impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
         llvm::LLVMMetadataAsValue(self.llcx(), metadata)
     }
 
-    // FIXME(autodiff): We should split `ConstCodegenMethods` to pull the reusable parts
-    // onto a trait that is also implemented for GenericCx.
-    pub(crate) fn get_const_i64(&self, n: u64) -> &'ll Value {
-        let ty = unsafe { llvm::LLVMInt64TypeInContext(self.llcx()) };
-        unsafe { llvm::LLVMConstInt(ty, n, llvm::False) }
+    pub(crate) fn get_const_int(&self, ty: &'ll Type, val: u64) -> &'ll Value {
+        let num_bits = self.int_width(ty).try_into().expect("integer width is too large for u32");
+        let ty = unsafe { llvm::LLVMIntTypeInContext(self.llcx(), num_bits) };
+        unsafe { llvm::LLVMConstInt(ty, val, llvm::False) }
     }
 
     pub(crate) fn get_function(&self, name: &str) -> Option<&'ll Value> {