Have the inst emitter add the !srcloc mdnode to the machine instr.

Have the asmprinter use the mdnode to scavenge a source location if
present.  Document this nonsense in langref.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100607 91177308-0d34-0410-b5e6-96231b3b80d8

docs/LangRef.html

@@ -2516,6 +2516,31 @@ call void asm alignstack "eieio", ""()
    documented here.  Constraints on what can be done (e.g. duplication, moving,
    etc need to be documented).  This is probably best done by reference to
    another document that covers inline asm from a holistic perspective.</p>
+</div>
+
+<div class="doc_subsubsection">
+<a name="inlineasm_md">Inline Asm Metadata</a>
+</div>
+
+<div class="doc_text">
+
+<p>The call instructions that wrap inline asm nodes may have a "!srcloc" MDNode
+   attached to it that contains a constant integer.  If present, the code
+   generator will use the integer as the location cookie value when report
+   errors through the LLVMContext error reporting mechanisms.  This allows a
+   front-end to corrolate backend errors that occur with inline asm back to the
+   source code that produced it.  For example:</p>
+
+<div class="doc_code">
+<pre>
+call void asm sideeffect "something bad", ""()<b>, !srcloc !42</b>
+...
+!42 = !{ i32 1234567 }
+</pre>
+</div>
+
+<p>It is up to the front-end to make sense of the magic numbers it places in the
+   IR.</p>
 
 </div>
 

lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp

@@ -13,6 +13,7 @@
 
 #define DEBUG_TYPE "asm-printer"
 #include "llvm/CodeGen/AsmPrinter.h"
+#include "llvm/Constants.h"
 #include "llvm/InlineAsm.h"
 #include "llvm/LLVMContext.h"
 #include "llvm/Module.h"
@@ -97,7 +98,7 @@ void AsmPrinter::EmitInlineAsm(const MachineInstr *MI) const {
   unsigned NumDefs = 0;
   for (; MI->getOperand(NumDefs).isReg() && MI->getOperand(NumDefs).isDef();
        ++NumDefs)
-    assert(NumDefs != NumOperands-1 && "No asm string?");
+    assert(NumDefs != NumOperands-2 && "No asm string?");
   
   assert(MI->getOperand(NumDefs).isSymbol() && "No asm string?");
 
@@ -123,6 +124,15 @@ void AsmPrinter::EmitInlineAsm(const MachineInstr *MI) const {
     OutStreamer.EmitRawText(Twine("\t")+MAI->getCommentString()+
                             MAI->getInlineAsmStart());
 
+  // Get the !srcloc metadata node if we have it, and decode the loc cookie from
+  // it.
+  unsigned LocCookie = 0;
+  if (const MDNode *SrcLoc = MI->getOperand(NumOperands-1).getMetadata()) {
+    if (SrcLoc->getNumOperands() != 0)
+      if (const ConstantInt *CI = dyn_cast<ConstantInt>(SrcLoc->getOperand(0)))
+        LocCookie = CI->getZExtValue();
+  }
+  
   // Emit the inline asm to a temporary string so we can emit it through
   // EmitInlineAsm.
   SmallString<256> StringData;
@@ -295,7 +305,7 @@ void AsmPrinter::EmitInlineAsm(const MachineInstr *MI) const {
     }
   }
   OS << '\n' << (char)0;  // null terminate string.
-  EmitInlineAsm(OS.str(), 0/*no loc cookie*/);
+  EmitInlineAsm(OS.str(), LocCookie);
   
   // Emit the #NOAPP end marker.  This has to happen even if verbose-asm isn't
   // enabled, so we use EmitRawText.

lib/CodeGen/SelectionDAG/InstrEmitter.cpp

@@ -769,6 +769,12 @@ EmitSpecialNode(SDNode *Node, bool IsClone, bool IsCloned,
         break;
       }
     }
+    
+    // Get the mdnode from the asm if it exists and add it to the instruction.
+    SDValue MDV = Node->getOperand(InlineAsm::Op_MDNode);
+    const MDNode *MD = cast<MDNodeSDNode>(MDV)->getMD();
+    MI->addOperand(MachineOperand::CreateMetadata(MD));
+    
     MBB->insert(InsertPos, MI);
     break;
   }