From 4faa8611c04e6a39cfc9aee10115946989f35ec7 Mon Sep 17 00:00:00 2001
From: Geoff Norton <grompf@gmail.com>
Date: Tue, 10 Feb 2015 21:56:48 -0800
Subject: [PATCH] Implement JIT_MemSet and JIT_MemCpy for clang

The windows build has a hand written version of these functions, but
modern systems should have an equivalent performant version of this.
We do need to wrap them to get the trap for a null reference exception,
but after that we can tail call directly.
---
 src/vm/CMakeLists.txt     |  1 +
 src/vm/amd64/crthelpers.S | 43 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 src/vm/amd64/crthelpers.S

diff --git a/src/vm/CMakeLists.txt b/src/vm/CMakeLists.txt
index f777e41..b89daac 100644
--- a/src/vm/CMakeLists.txt
+++ b/src/vm/CMakeLists.txt
@@ -326,6 +326,7 @@ set(VM_SOURCES_WKS_AMD64_ASM
 
 else()
 set(VM_SOURCES_WKS_AMD64_ASM
+    ${AMD64_SOURCES_DIR}/crthelpers.S
     ${AMD64_SOURCES_DIR}/jithelpers_fastwritebarriers.S
     ${AMD64_SOURCES_DIR}/jithelpers_slow.S
     ${AMD64_SOURCES_DIR}/jithelpers_fast.S
diff --git a/src/vm/amd64/crthelpers.S b/src/vm/amd64/crthelpers.S
new file mode 100644
index 0000000..0b36e00
--- /dev/null
+++ b/src/vm/amd64/crthelpers.S
@@ -0,0 +1,43 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Copyright (c) Geoff Norton. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information. 
+//
+
+.intel_syntax noprefix
+#include "unixasmmacros.inc"
+#include "asmconstants.h"
+
+// JIT_MemSet/JIT_MemCpy
+//
+// It is IMPORANT that the exception handling code is able to find these guys
+// on the stack, but on non-windows platforms we can just defer to the platform
+// implementation.
+// 
+
+LEAF_ENTRY JIT_MemSet, _TEXT
+        test rdx, rdx
+        jz   Exit_MemSet
+
+        cmp  byte ptr [rdi], 0
+
+        jmp  C_FUNC(memset)
+
+Exit_MemSet:
+        ret
+
+LEAF_END JIT_MemSet, _TEXT
+
+LEAF_ENTRY JIT_MemCpy, _TEXT
+        test rdx, rdx
+        jz   Exit_MemCpy
+
+        cmp  byte ptr [rdi], 0
+        cmp  byte ptr [rsi], 0
+
+        jmp  C_FUNC(memcpy)
+
+Exit_MemCpy:
+        ret
+
+LEAF_END JIT_MemCpy, _TEXT
-- 
2.7.4