[LLVMbugs] [Bug 23419] New: Exploit LCDFR/LPDFR/LNDFR instructions

[bugzilla-daemon at llvm.org]

https://llvm.org/bugs/show_bug.cgi?id=23419

            Bug ID: 23419
           Summary: Exploit LCDFR/LPDFR/LNDFR instructions
           Product: libraries
           Version: trunk
          Hardware: Other
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: SystemZ
          Assignee: unassignedbugs at nondot.org
          Reporter: uweigand at de.ibm.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

System z currently uses the IEEE-specific forms of LOAD COMPLEMENT,
LOAD NEGATIVE and LOAD POSITIVE.  However, in cases where we don't
need the resulting condition codes, we can instead use the generic
forms of those instructions (e.g. LCDFR instead of LCDBR).

To do so, we should always start by emitting the generic form, and
if it turns out we can actually use the condition code, we can convert
back to the IEEE-specific forms during the SystemZElimCompare pass
by listing them in SystemZInstrInfo::getLoadAndTest.

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