[bindings/go] Add ParseIR

[aykevl]

Summary

This commit adds a single method to the Context object to parse a textual IR file. This is useful for reading input IR in unit tests.

[whitequark]

LGTM

[aykevl]

@hans can you help me out? I accidentally pushed to the release_80 branch instead of to trunk, because of a mistake in my git-llvm configuration. I think it should be reverted.
Also see IRC logs starting 17:52 UTC on this day (Sunday).

I'll take a look at adding a check in git-llvm to avoid mistakes like this in the future.

UPDATE: here it is: https://reviews.llvm.org/D66395

[hans]

In D66379#1634484, @aykevl wrote:

@hans can you help me out? I accidentally pushed to the release_80 branch instead of to trunk, because of a mistake in my git-llvm configuration. I think it should be reverted.
Also see IRC logs starting 17:52 UTC on this day (Sunday).

No problem, thanks for letting me know. I've reverted in r369350.

llvm/branches/release_80/bindings/go/llvm/irreader.go

+//===- irreader.go - Bindings for irreader --------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines bindings for the irreader component.
+//
+//===----------------------------------------------------------------------===//
+
+package llvm
+
+/*
+#include "llvm-c/IRReader.h"
+#include <stdlib.h>
+*/
+import "C"
+
+import (
+  "errors"
+  "unsafe"
+)
+
+// ParseIR parses the textual IR given in the memory buffer and returns a new
+// LLVM module in this context.
+func (c *Context) ParseIR(buf MemoryBuffer) (Module, error) {
+  var m Module
+  var errmsg *C.char
+  if C.LLVMParseIRInContext(c.C, buf.C, &m.C, &errmsg) != 0 {
+    err := errors.New(C.GoString(errmsg))
+    C.free(unsafe.Pointer(errmsg))
+    return Module{}, err
+  }
+  return m, nil
+}