From 79ffdc7581f6d6296f37857e483a524f22b6c9e7 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Wed, 17 Nov 2010 08:20:42 +0000
Subject: [PATCH] With the newly simplified SourceMgr interfaces and the
 generalized SrcMgrDiagHandler, we can improve clang diagnostics for inline
 asm: instead of reporting them on a source line of the original line, we can
 report it on the correct line wherever the string literal came from. For
 something like this:

void foo() {
  asm("push %rax\n"
      ".code32\n");
}

we used to get this: (note that the line in t.c isn't helpful)

t.c:4:7: error: warning: ignoring directive for now
  asm("push %rax\n"
      ^
<inline asm>:2:1: note: instantiated into assembly here
.code32
^

now we get:

t.c:5:8: error: warning: ignoring directive for now
      ".code32\n"
       ^
<inline asm>:2:1: note: instantiated into assembly here
.code32
^

Note that we're pointing to line 5 properly now.

llvm-svn: 119488
---
 llvm/docs/LangRef.html                             |  7 ++++---
 .../lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp | 14 +++++++++++---
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/llvm/docs/LangRef.html b/llvm/docs/LangRef.html
index f15f139aeb38..1c31e4533697 100644
--- a/llvm/docs/LangRef.html
+++ b/llvm/docs/LangRef.html
@@ -2625,8 +2625,8 @@ call void asm alignstack "eieio", ""()
 <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
+   attached to it that contains a list of constant integers.  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 correlate backend errors that occur with inline asm back to the
    source code that produced it.  For example:</p>
@@ -2638,7 +2638,8 @@ call void asm sideeffect "something bad", ""()<b>, !srcloc !42</b>
 </pre>
 
 <p>It is up to the front-end to make sense of the magic numbers it places in the
-   IR.</p>
+   IR.  If the MDNode contains multiple constants, the code generator will use
+   the one that corresponds to the line of the asm that the error occurs on.</p>
 
 </div>
 
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
index 9e5d679aa3c2..ff9ecf2dbd07 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
@@ -49,11 +49,19 @@ static void SrcMgrDiagHandler(const SMDiagnostic &Diag, void *diagInfo) {
   SrcMgrDiagInfo *DiagInfo = static_cast<SrcMgrDiagInfo *>(diagInfo);
   assert(DiagInfo && "Diagnostic context not passed down?");
   
+  // If the inline asm had metadata associated with it, pull out a location
+  // cookie corresponding to which line the error occurred on.
   unsigned LocCookie = 0;
-  if (const MDNode *LocInfo = DiagInfo->LocInfo) 
-    if (LocInfo->getNumOperands() > 0)
-      if (const ConstantInt *CI = dyn_cast<ConstantInt>(LocInfo->getOperand(0)))
+  if (const MDNode *LocInfo = DiagInfo->LocInfo) {
+    unsigned ErrorLine = Diag.getLineNo()-1;
+    if (ErrorLine >= LocInfo->getNumOperands())
+      ErrorLine = 0;
+    
+    if (LocInfo->getNumOperands() != 0)
+      if (const ConstantInt *CI =
+          dyn_cast<ConstantInt>(LocInfo->getOperand(ErrorLine)))
         LocCookie = CI->getZExtValue();
+  }
   
   DiagInfo->DiagHandler(Diag, DiagInfo->DiagContext, LocCookie);
 }