From d71449a3f7681dd845504b72387bf68be7cc0d87 Mon Sep 17 00:00:00 2001
From: David Lamparter <equinox@diac24.net>
Date: Tue, 23 Mar 2021 20:19:10 +0100
Subject: tools: grok struct member calls in frr-llvm-cg

Calling a function pointer embedded in a struct is quite common & having
this listed in the call graph is useful.

Signed-off-by: David Lamparter <equinox@diac24.net>
---
 tools/frr-llvm-debuginfo.cpp | 112 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 tools/frr-llvm-debuginfo.cpp

(limited to 'tools/frr-llvm-debuginfo.cpp')

diff --git a/tools/frr-llvm-debuginfo.cpp b/tools/frr-llvm-debuginfo.cpp
new file mode 100644
index 0000000000..ed3ad956b8
--- /dev/null
+++ b/tools/frr-llvm-debuginfo.cpp
@@ -0,0 +1,112 @@
+// This is free and unencumbered software released into the public domain.
+//
+// Anyone is free to copy, modify, publish, use, compile, sell, or
+// distribute this software, either in source code form or as a compiled
+// binary, for any purpose, commercial or non-commercial, and by any
+// means.
+//
+// In jurisdictions that recognize copyright laws, the author or authors
+// of this software dedicate any and all copyright interest in the
+// software to the public domain. We make this dedication for the benefit
+// of the public at large and to the detriment of our heirs and
+// successors. We intend this dedication to be an overt act of
+// relinquishment in perpetuity of all present and future rights to this
+// software under copyright law.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+// IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+// OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+// OTHER DEALINGS IN THE SOFTWARE.
+//
+// For more information, please refer to <http://unlicense.org/>
+
+#include <llvm-c/BitReader.h>
+#include <llvm-c/BitWriter.h>
+#include <llvm-c/Core.h>
+#include <llvm-c/DebugInfo.h>
+
+#include <llvm/IR/Module.h>
+#include <llvm/IR/Value.h>
+#include <llvm/IR/Type.h>
+#include <llvm/IR/DebugInfo.h>
+#include <llvm/IR/DebugInfoMetadata.h>
+#include <llvm/Support/raw_ostream.h>
+
+#include <map>
+
+#include "frr-llvm-debuginfo.h"
+
+/* llvm::DebugInfoFinder is unfortunately not exposed in the llvm-c API... */
+
+struct dbginfo {
+	llvm::DebugInfoFinder finder;
+	std::map<std::string, llvm::DICompositeType *> tab;
+};
+
+struct dbginfo *dbginfo_load(LLVMModuleRef _mod)
+{
+	llvm::Module *mod = llvm::unwrap(_mod);
+	struct dbginfo *info = new dbginfo();
+
+	info->finder.processModule(*mod);
+
+	for (auto ty : info->finder.types()) {
+		if (ty->getMetadataID() != llvm::Metadata::DICompositeTypeKind)
+			continue;
+
+		llvm::DICompositeType *cty = (llvm::DICompositeType *)ty;
+		/* empty forward declarations aka "struct foobar;" */
+		if (cty->getElements().size() == 0)
+			continue;
+
+		info->tab.emplace(std::move(ty->getName().str()), cty);
+	}
+
+	return info;
+}
+
+bool dbginfo_struct_member(struct dbginfo *info, LLVMTypeRef _typ,
+			   unsigned long long idx, char **struct_name,
+			   char **member_name)
+{
+	*struct_name = NULL;
+	*member_name = NULL;
+
+	llvm::Type *typ = llvm::unwrap(_typ);
+
+	if (!typ->isStructTy())
+		return false;
+
+	llvm::StructType *styp = (llvm::StructType *)typ;
+	auto sname = styp->getStructName();
+
+	if (!sname.startswith("struct."))
+		return false;
+	sname = sname.drop_front(7);
+
+	size_t dot = sname.find_last_of(".");
+	if (dot != sname.npos)
+		sname = sname.take_front(dot);
+
+	auto item = info->tab.find(sname.str());
+	if (item == info->tab.end())
+		return false;
+
+	auto elements = item->second->getElements();
+	if (idx >= elements.size())
+		return false;
+
+	auto elem = elements[idx];
+
+	if (elem->getMetadataID() != llvm::Metadata::DIDerivedTypeKind)
+		return false;
+
+	llvm::DIDerivedType *dtyp = (llvm::DIDerivedType *)elem;
+
+	*struct_name = strdup(sname.str().c_str());
+	*member_name = strdup(dtyp->getName().str().c_str());
+	return true;
+}
-- 
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