From 4514db2bfb2a93812f899955f1357733292f7b00 Mon Sep 17 00:00:00 2001
From: Colin LeMahieu <colinl@codeaurora.org>
Date: Sun, 7 Jun 2015 01:46:24 +0000
Subject: [PATCH] Teaching llvm-mc how to understand the defsym command line
 option.  This allows integer-constant symbols to be defined on the command
 line and used during assembly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239240 91177308-0d34-0410-b5e6-96231b3b80d8
---
 test/MC/AsmParser/defsym.s        | 20 ++++++++++++++++++++
 test/MC/AsmParser/defsym_error1.s |  2 ++
 test/MC/AsmParser/defsym_error2.s |  2 ++
 tools/llvm-mc/llvm-mc.cpp         | 26 ++++++++++++++++++++++++++
 4 files changed, 50 insertions(+)
 create mode 100644 test/MC/AsmParser/defsym.s
 create mode 100644 test/MC/AsmParser/defsym_error1.s
 create mode 100644 test/MC/AsmParser/defsym_error2.s

diff --git a/test/MC/AsmParser/defsym.s b/test/MC/AsmParser/defsym.s
new file mode 100644
index 00000000000..06981f54046
--- /dev/null
+++ b/test/MC/AsmParser/defsym.s
@@ -0,0 +1,20 @@
+# RUN: llvm-mc -filetype=obj -triple=i386-unknown-elf -defsym a=7 -defsym b=11 %s | llvm-objdump -t - | FileCheck %s
+
+.ifndef a
+.err 
+.endif
+
+.if a<>7
+.err
+.endif
+
+.ifndef b
+.err
+.endif
+
+.if b<>11
+.err
+.endif
+
+# CHECK: 00000007         *ABS*  00000000 a
+# CHECK: 0000000b         *ABS*  00000000 b
\ No newline at end of file
diff --git a/test/MC/AsmParser/defsym_error1.s b/test/MC/AsmParser/defsym_error1.s
new file mode 100644
index 00000000000..872577844d4
--- /dev/null
+++ b/test/MC/AsmParser/defsym_error1.s
@@ -0,0 +1,2 @@
+# RUN: not llvm-mc -filetype=obj -triple=i386-unknown-elf -defsym aaoeuaoeu %s 2>&1 | FileCheck %s
+# CHECK: defsym must be of the form: sym=value
diff --git a/test/MC/AsmParser/defsym_error2.s b/test/MC/AsmParser/defsym_error2.s
new file mode 100644
index 00000000000..ec4cc79182f
--- /dev/null
+++ b/test/MC/AsmParser/defsym_error2.s
@@ -0,0 +1,2 @@
+# RUN: not llvm-mc -filetype=obj -triple=i386-unknown-elf -defsym a=a %s 2>&1 | FileCheck %s
+# CHECK: error: Value is not an integer: a
diff --git a/tools/llvm-mc/llvm-mc.cpp b/tools/llvm-mc/llvm-mc.cpp
index 6a8b49373df..9a9185c7523 100644
--- a/tools/llvm-mc/llvm-mc.cpp
+++ b/tools/llvm-mc/llvm-mc.cpp
@@ -70,6 +70,9 @@ static cl::opt<bool>
 PrintImmHex("print-imm-hex", cl::init(false),
             cl::desc("Prefer hex format for immediate values"));
 
+static cl::list<std::string>
+DefineSymbol("defsym", cl::desc("Defines a symbol to be an integer constant"));
+
 enum OutputFileType {
   OFT_Null,
   OFT_AssemblyFile,
@@ -316,6 +319,26 @@ static int AsLexInput(SourceMgr &SrcMgr, MCAsmInfo &MAI,
   return Error;
 }
 
+static int fillCommandLineSymbols(MCAsmParser &Parser){
+  for(auto &I: DefineSymbol){
+    auto Pair = StringRef(I).split('=');
+    if(Pair.second.empty()){
+      errs() << "error: defsym must be of the form: sym=value: " << I;
+      return 1;
+    }
+    int64_t Value;
+    if(Pair.second.getAsInteger(0, Value)){
+      errs() << "error: Value is not an integer: " << Pair.second;
+      return 1;
+    }
+    auto &Context = Parser.getContext();
+    auto Symbol = Context.getOrCreateSymbol(Pair.first);
+    Parser.getStreamer().EmitAssignment(Symbol,
+                                        MCConstantExpr::create(Value, Context));
+  }
+  return 0;
+}
+
 static int AssembleInput(const char *ProgName, const Target *TheTarget,
                          SourceMgr &SrcMgr, MCContext &Ctx, MCStreamer &Str,
                          MCAsmInfo &MAI, MCSubtargetInfo &STI,
@@ -331,6 +354,9 @@ static int AssembleInput(const char *ProgName, const Target *TheTarget,
     return 1;
   }
 
+  int SymbolResult = fillCommandLineSymbols(*Parser);
+  if(SymbolResult)
+    return SymbolResult;
   Parser->setShowParsedOperands(ShowInstOperands);
   Parser->setTargetParser(*TAP);