From 2bc89cf1f02daac1e207e8dea4fcb7fb9481701c Mon Sep 17 00:00:00 2001
From: Saleem Abdulrasool <compnerd@compnerd.org>
Date: Wed, 17 Dec 2014 17:52:30 +0000
Subject: [PATCH] CodeGen: implement __emit intrinsic

For MSVC compatibility, add the `__emit' builtin. This is used in the Windows
SDK headers, and must therefore be implemented as a builtin rather than an
intrinsic.

The `__emit' builtin provides a mechanism to emit a 16-bit opcode instruction
into the stream. The value must be a compile time constant expression. No
guarantees are made about the CPU and memory states after the execution of the
instruction.

Due to the unchecked nature of the builtin, only support this on Windows on ARM.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@224438 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/BuiltinsARM.def           |  2 ++
 lib/CodeGen/CGBuiltin.cpp                     | 22 +++++++++++++++++++
 test/CodeGen/builtins-arm-msvc-compat-error.c |  6 +++++
 test/CodeGen/builtins-arm-msvc-compat-only.c  | 19 ++++++++++++++++
 4 files changed, 49 insertions(+)
 create mode 100644 test/CodeGen/builtins-arm-msvc-compat-error.c
 create mode 100644 test/CodeGen/builtins-arm-msvc-compat-only.c

diff --git a/include/clang/Basic/BuiltinsARM.def b/include/clang/Basic/BuiltinsARM.def
index 1f2f9a3840..9091ad4d75 100644
--- a/include/clang/Basic/BuiltinsARM.def
+++ b/include/clang/Basic/BuiltinsARM.def
@@ -85,6 +85,8 @@ BUILTIN(__builtin_arm_isb, "vUi", "nc")
 BUILTIN(__builtin_arm_prefetch, "vvC*UiUi", "nc")
 
 // MSVC
+LANGBUILTIN(__emit, "vIUiC", "", ALL_MS_LANGUAGES)
+
 LANGBUILTIN(__yield, "v", "", ALL_MS_LANGUAGES)
 LANGBUILTIN(__wfe, "v", "", ALL_MS_LANGUAGES)
 LANGBUILTIN(__wfi, "v", "", ALL_MS_LANGUAGES)
diff --git a/lib/CodeGen/CGBuiltin.cpp b/lib/CodeGen/CGBuiltin.cpp
index 155545d4c9..fca60d50c5 100644
--- a/lib/CodeGen/CGBuiltin.cpp
+++ b/lib/CodeGen/CGBuiltin.cpp
@@ -20,7 +20,9 @@
 #include "clang/Basic/TargetBuiltins.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/CodeGen/CGFunctionInfo.h"
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/Intrinsics.h"
 
 using namespace clang;
@@ -3165,6 +3167,26 @@ Value *CodeGenFunction::EmitARMBuiltinExpr(unsigned BuiltinID,
   if (auto Hint = GetValueForARMHint(BuiltinID))
     return Hint;
 
+  if (BuiltinID == ARM::BI__emit) {
+    bool IsThumb = getTarget().getTriple().getArch() == llvm::Triple::thumb;
+    llvm::FunctionType *FTy =
+        llvm::FunctionType::get(VoidTy, /*Variadic=*/false);
+
+    APSInt Value;
+    if (!E->getArg(0)->EvaluateAsInt(Value, CGM.getContext()))
+      llvm_unreachable("Sema will ensure that the parameter is constant");
+
+    uint64_t ZExtValue = Value.zextOrTrunc(IsThumb ? 16 : 32).getZExtValue();
+
+    llvm::InlineAsm *Emit =
+        IsThumb ? InlineAsm::get(FTy, ".inst.n 0x" + utohexstr(ZExtValue), "",
+                                 /*SideEffects=*/true)
+                : InlineAsm::get(FTy, ".inst 0x" + utohexstr(ZExtValue), "",
+                                 /*SideEffects=*/true);
+
+    return Builder.CreateCall(Emit);
+  }
+
   if (BuiltinID == ARM::BI__builtin_arm_dbg) {
     Value *Option = EmitScalarExpr(E->getArg(0));
     return Builder.CreateCall(CGM.getIntrinsic(Intrinsic::arm_dbg), Option);
diff --git a/test/CodeGen/builtins-arm-msvc-compat-error.c b/test/CodeGen/builtins-arm-msvc-compat-error.c
new file mode 100644
index 0000000000..29469deb6a
--- /dev/null
+++ b/test/CodeGen/builtins-arm-msvc-compat-error.c
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -triple thumbv7-windows -fms-extensions -verify %s
+
+void emit_error(unsigned int opcode) {
+  __emit(opcode); // expected-error {{argument to '__emit' must be a constant integer}}
+}
+
diff --git a/test/CodeGen/builtins-arm-msvc-compat-only.c b/test/CodeGen/builtins-arm-msvc-compat-only.c
new file mode 100644
index 0000000000..db82ca4066
--- /dev/null
+++ b/test/CodeGen/builtins-arm-msvc-compat-only.c
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -triple thumbv7-windows -fms-extensions -emit-llvm -o - %s \
+// RUN:     | FileCheck %s -check-prefix CHECK-MSVC
+// RUN: %clang_cc1 -triple armv7-eabi -emit-llvm %s -o /dev/null 2>&1 \
+// RUN:     | FileCheck %s -check-prefix CHECK-EABI
+// REQUIRES: arm-registered-target
+
+void emit() {
+  __emit(0xdefe);
+}
+
+// CHECK-MSVC: call void asm sideeffect ".inst.n 0xDEFE", ""()
+// CHECK-EABI: warning: implicit declaration of function '__emit' is invalid in C99
+
+void emit_truncated() {
+  __emit(0x11110000); // movs r0, r0
+}
+
+// CHECK-MSVC: call void asm sideeffect ".inst.n 0x0", ""()
+
-- 
2.50.1