[llvm] r352204 - [JSON] Work around excess-precision issue when comparing T_Integer numbers.

[Sam McCall via llvm-commits]

Author: sammccall
Date: Fri Jan 25 07:05:33 2019
New Revision: 352204

URL: http://llvm.org/viewvc/llvm-project?rev=352204&view=rev
Log:
[JSON] Work around excess-precision issue when comparing T_Integer numbers.

Reviewers: bkramer

Subscribers: kristina, llvm-commits

Differential Revision: https://reviews.llvm.org/D57237

Modified:
    llvm/trunk/include/llvm/Support/JSON.h
    llvm/trunk/lib/Support/JSON.cpp

Modified: llvm/trunk/include/llvm/Support/JSON.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/JSON.h?rev=352204&r1=352203&r2=352204&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/JSON.h (original)
+++ llvm/trunk/include/llvm/Support/JSON.h Fri Jan 25 07:05:33 2019
@@ -480,6 +480,7 @@ private:
   mutable llvm::AlignedCharArrayUnion<bool, double, int64_t, llvm::StringRef,
                                       std::string, json::Array, json::Object>
       Union;
+  friend bool operator==(const Value &, const Value &);
 };
 
 bool operator==(const Value &, const Value &);

Modified: llvm/trunk/lib/Support/JSON.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/JSON.cpp?rev=352204&r1=352203&r2=352204&view=diff
==============================================================================
--- llvm/trunk/lib/Support/JSON.cpp (original)
+++ llvm/trunk/lib/Support/JSON.cpp Fri Jan 25 07:05:33 2019
@@ -181,6 +181,12 @@ bool operator==(const Value &L, const Va
   case Value::Boolean:
     return *L.getAsBoolean() == *R.getAsBoolean();
   case Value::Number:
+    // Workaround for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=323
+    // The same integer must convert to the same double, per the standard.
+    // However we see 64-vs-80-bit precision comparisons with gcc-7 -O3 -m32.
+    // So we avoid floating point promotion for exact comparisons.
+    if (L.Type == Value::T_Integer || R.Type == Value::T_Integer)
+      return L.getAsInteger() == R.getAsInteger();
     return *L.getAsNumber() == *R.getAsNumber();
   case Value::String:
     return *L.getAsString() == *R.getAsString();