https://issues.dlang.org/show_bug.cgi?id=15861

          Issue ID: 15861
           Summary: Wrong double-to-string conversion with -O
           Product: D
           Version: D2
          Hardware: x86
                OS: All
            Status: NEW
          Keywords: wrong-code
          Severity: regression
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: thecybershadow@gmail.com

///////////////////////// test.d ///////////////////////// import std.format;

void main()
{
    assert(format("%.18g", 4286853117.0) == "4286853117");
}
//////////////////////////////////////////////////////////

Passes without -O, asserts with -O.

Introduced in https://github.com/D-Programming-Language/dmd/pull/4911

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