[LLVMbugs] [Bug 3497] New: memory barriers not lowered correctly on x86/x86-64

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=3497

           Summary: memory barriers not lowered correctly on x86/x86-64
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: edwintorok at gmail.com
                CC: llvmbugs at cs.uiuc.edu


__sync_synchronize is lowered to nothing on x86/x86-64, while gcc lowers it to
mfence.

Testcase:
void foo() {     __sync_synchronize(); }

LLVM-IR:
; ModuleID = 'x.c'
target datalayout =
"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
target triple = "x86_64-unknown-linux-gnu"

define void @foo() nounwind {
entry:
        tail call void @llvm.memory.barrier(i1 true, i1 true, i1 true, i1 true,
i1 false)
        ret void
}

declare void @llvm.memory.barrier(i1, i1, i1, i1, i1) nounwind

Assembly:
foo:
        nop
        ret
        .size   foo, .-foo


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