[LLVMbugs] [Bug 2985] New: Invalid code generated for cpu2000/gcc with -mthumb

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=2985

           Summary: Invalid code generated for cpu2000/gcc with -mthumb
           Product: libraries
           Version: trunk
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: major
          Priority: P2
         Component: Backend: ARM
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: evan.cheng at apple.com
                CC: llvmbugs at cs.uiuc.edu


llvm generates illegal assembly in Thumb:
sub r5,sp,r2

The issue is the Thumb backend is treating all integer registers in the same
register class. The register coalescer doesn't know it cannot coalesce a copy
from sp into a use.

I have attached a reduced test case. Just run llc on it to see the bad
assembly.


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