[llvm-commits] Commit 141135 breaks thumb assembly

[James Molloy]

Hi Owen,

Your commit 141135 causes incorrect assembly to be output in Thumb mode. You modified MCAsmStreamer to emit mapping symbols at the beginning of code and data sections ('$a.0', '$d.0'). In thumb mode, it will also output an '$a' which is incorrect, as $a says that the following code is ARM-mode.

After assembly with GNU As, the correct '$t' mapping symbol is added by the assembler, which causes both a $a and a $t to be at the same address and confuses our linker (and would confuse most linkers and disassembly tools!):

.LBB0_2:                                @ %switch.case.1
$a.0:
        movw    r0, :lower16:Int_Glob
        movt    r0, :upper16:Int_Glob
        ldr     r0, [r0]
        cmp     r0, #101
        blt     .LBB0_4

Assembles to:

    $a
    $t
        0x00000018:    f2400000    @...    MOVW     r0,#:LOWER16: Int_Glob
        0x0000001c:    f2c00000    ....    MOVT     r0,#:UPPER16: Int_Glob
        0x00000020:    6800        .h      LDR      r0,[r0,#0]
        0x00000022:    2865        e(      CMP      r0,#0x65
        0x00000024:    db01        ..      BLT      {pc}+0x6 ; 0x2a

This is incorrect by the ABI - the mapping symbols contradict.

Could you please fix this?

Cheers,

James

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