[LLVMbugs] [Bug 14113] New: llvm incorrectly passes byval pointers in registers to x86_fastcallcc functions

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=14113

             Bug #: 14113
           Summary: llvm incorrectly passes byval pointers in registers to
                    x86_fastcallcc functions
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: ASSIGNED
          Severity: enhancement
          Priority: P
         Component: Backend: X86
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: rafael.espindola at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Given

struct foo {
  int x;
};
void __attribute__((fastcall)) foo(struct foo y);

void bar(struct foo y) {
  foo(y);
}

gcc produces

bar:
        subl    $24, %esp
        pushl   28(%esp)
        call    foo
        addl    $24, %esp
        ret

but clang produces

bar:                                    # @bar
# BB#0:
        subl    $12, %esp
        movl    16(%esp), %ecx
        calll   foo
        addl    $12, %esp
        ret

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