[LLVMbugs] [Bug 23912] New: Handling of ARM Errata 602117 (and testcase) is broken

[bugzilla-daemon at llvm.org]

https://llvm.org/bugs/show_bug.cgi?id=23912

            Bug ID: 23912
           Summary: Handling of ARM Errata 602117 (and testcase) is broken
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: ARM
          Assignee: unassignedbugs at nondot.org
          Reporter: matze at braunis.de
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

While working on the ARMLoadStoreOptimizer code I realized that the handling of
Cortex-M3 Errata 602117 and the llvm-lit test that checks for it are faulty. If
you use the following test instead, you still see an invalid ldrd created, even
with -mcpu=cortex-m3.

; we call the following two to force values into specific registers.
declare i64* @get_ptr()
declare void @use_i64(i64 %v)

define void @test_ldrd(i64 %a) nounwind readonly {
  %ptr = call i64* @get_ptr()
  %v = load i64, i64* %ptr, align 8
  call void @use_i64(i64 %v)
  ret void
}

Results in:
...
    bl    _get_ptr
    ldrd    r0, r1, [r0]
    bl    _use_i64
...

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