[LLVMbugs] [Bug 18665] New: CLFLUSH requires HasSSE2 but instruction availability isn't connected to SSE2

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=18665

            Bug ID: 18665
           Summary: CLFLUSH requires HasSSE2 but instruction availability
                    isn't connected to SSE2
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: sschiffli at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

In lib\Target\X86\X86InstrSSE.td the CLFLUSH instruction is declared with
Requires<[HasSSE2]>, but if you read the Intel instruction manual of CLFLUSH it
says the following:

"The CLFLUSH instruction was introduced with the SSE2 extensions; however,
because it has its own CPUID feature flag, it can be implemented in IA-32
processors that do not include the SSE2 extensions. Also, detecting the
presence of the SSE2 extensions with the CPUID instruction does not guarantee
that the CLFLUSH instruction is implemented in the processor."

I believe a new X86Subtarget feature flag should be implemented which
determines the availability of CLFLUSH.

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