add a new TGError class and use it to propagate location info with
errors when thrown.  This gets us nice errors like this from tblgen:

CMOVL32rr: 	(set GR32:i32:$dst, (X86cmov GR32:$src1, GR32:$src2))
/Users/sabre/llvm/Debug/bin/tblgen: error:
Included from X86.td:116:
Parsing X86InstrInfo.td:922: In CMOVL32rr: X86cmov node requires exactly 4 operands!
def CMOVL32rr : I<0x4C, MRMSrcReg,       // if <s, GR32 = GR32
^

instead of just:

CMOVL32rr: 	(set GR32:i32:$dst, (X86cmov GR32:$src1, GR32:$src2))
/Users/sabre/llvm/Debug/bin/tblgen: In CMOVL32rr: X86cmov node requires exactly 4 operands!

This is all I plan to do with this, but it should be easy enough to improve if anyone 
cares (e.g. keeping more loc info in "dag" expr records in tblgen.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66898 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/TableGen/CodeGenDAGPatterns.cpp b/utils/TableGen/CodeGenDAGPatterns.cpp
index 6e7dd1e..6af0515 100644
--- a/utils/TableGen/CodeGenDAGPatterns.cpp
+++ b/utils/TableGen/CodeGenDAGPatterns.cpp
@@ -1113,7 +1113,7 @@
 
 void TreePattern::error(const std::string &Msg) const {
   dump();
-  throw "In " + TheRecord->getName() + ": " + Msg;
+  throw TGError(TheRecord->getLoc(), "In " + TheRecord->getName() + ": " + Msg);
 }
 
 TreePatternNode *TreePattern::ParseTreePattern(DagInit *Dag) {