https://issues.dlang.org/show_bug.cgi?id=14456

          Issue ID: 14456
           Summary: dmd doesn't call C functions with large structures
                    correctly
           Product: D
           Version: D1
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P1
         Component: DMD
          Assignee: nobody@puremagic.com
          Reporter: andrew.stevenson@sociomantic.com

Created attachment 1513
  --> https://issues.dlang.org/attachment.cgi?id=1513&action=edit
example code

On Linux/amd64 an argument to a C function which is a structure larger than 64 bits should be passed across multiple registers. Making this call with DMD however does something else (probably trying to pass on the stack).

I attach some example code to demonstrate the problem. "make c" produces a binary from C code and "make d" produces a binary from D calling into C. Both should produce the same output.

I currently use a workaround of calling the C function via inline ASM. The correct ASM for the attached example would be something like:

mov RDI, qword ptr a;
mov RSI, qword ptr a + 8;
call prettify;

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