[llvm] r343984 - Fix incorrect Twine usage in CFGPrinter

[Kristina Brooks via llvm-commits]

Author: kristina
Date: Mon Oct  8 10:29:39 2018
New Revision: 343984

URL: http://llvm.org/viewvc/llvm-project?rev=343984&view=rev
Log:
Fix incorrect Twine usage in CFGPrinter

CFGPrinter (-view-cfg, -dot-cfg) invokes an undefined behaviour (dangling
pointer to rvalue) on IR files with branch weights. This patch fixes the
problem caused by Twine initialization and string conversion split into
two statements.

This change fixes the bug 37019. A similar patch to this problem was
provided in the llvmlite project

Patch by mcopik (Marcin Copik).

Differential Revision: https://reviews.llvm.org/D52933


Added:
    llvm/trunk/test/Other/cfg-printer-branch-weights.ll
Modified:
    llvm/trunk/include/llvm/Analysis/CFGPrinter.h

Modified: llvm/trunk/include/llvm/Analysis/CFGPrinter.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/CFGPrinter.h?rev=343984&r1=343983&r2=343984&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/CFGPrinter.h (original)
+++ llvm/trunk/include/llvm/Analysis/CFGPrinter.h Mon Oct  8 10:29:39 2018
@@ -172,8 +172,7 @@ struct DOTGraphTraits<const Function*> :
 
     // Prepend a 'W' to indicate that this is a weight rather than the actual
     // profile count (due to scaling).
-    Twine Attrs = "label=\"W:" + Twine(Weight->getZExtValue()) + "\"";
-    return Attrs.str();
+    return ("label=\"W:" + Twine(Weight->getZExtValue()) + "\"").str();
   }
 };
 } // End llvm namespace

Added: llvm/trunk/test/Other/cfg-printer-branch-weights.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Other/cfg-printer-branch-weights.ll?rev=343984&view=auto
==============================================================================
--- llvm/trunk/test/Other/cfg-printer-branch-weights.ll (added)
+++ llvm/trunk/test/Other/cfg-printer-branch-weights.ll Mon Oct  8 10:29:39 2018
@@ -0,0 +1,19 @@
+;RUN: opt < %s -analyze -dot-cfg 2>/dev/null
+;RUN: FileCheck %s -input-file=cfg.f.dot
+
+define void @f(i32) {
+entry:
+  %check = icmp sgt i32 %0, 0
+  br i1 %check, label %if, label %exit, !prof !0
+
+; CHECK: label="W:1"
+; CHECK-NOT: ["];
+if:                     ; preds = %entry
+  br label %exit
+; CHECK: label="W:200"
+; CHECK-NOT: ["];
+exit:                   ; preds = %entry, %if
+  ret void
+}
+
+!0 = !{!"branch_weights", i32 1, i32 200}