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[llvm][ARM] Allow MOVT and MOVW on the offset between two labels #168072

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Merged
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Nov 18, 2025
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[llvm][ARM] Allow MOVT and MOVW on the offset between two labels #168072

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[llvm][ARM] Allow MOVT and MOVW on the offset between two labels
hwti Nov 14, 2025
693ac07
fixup! [llvm][ARM] Allow MOVT and MOVW on the offset between two labels
hwti Nov 18, 2025
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2 changes: 1 addition & 1 deletion llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -428,7 +428,7 @@ unsigned ARMAsmBackend::adjustFixupValue(const MCAssembler &Asm,
// signed 16bit range.
if ((Kind == ARM::fixup_arm_movw_lo16 || Kind == ARM::fixup_arm_movt_hi16 ||
Kind == ARM::fixup_t2_movw_lo16 || Kind == ARM::fixup_t2_movt_hi16) &&
(Addend < minIntN(16) || Addend > maxIntN(16))) {
!Target.isAbsolute() && (Addend < minIntN(16) || Addend > maxIntN(16))) {
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@efriedma-quic efriedma-quic Nov 14, 2025

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Maybe could use IsResolved here instead? I guess it's basically the same thing in this context.

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@hwti hwti Nov 18, 2025

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OK, changed to !IsResolved.

Ctx.reportError(Fixup.getLoc(), "Relocation Not In Range");
return 0;
}
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14 changes: 14 additions & 0 deletions llvm/test/MC/ARM/arm-movt-movw-absolute-pass.s
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@@ -0,0 +1,14 @@
@RUN: llvm-mc -triple armv7-eabi -filetype obj -o - %s 2>&1 | FileCheck %s

.text
a:
movw r1, #:lower16:b - a + 65536
movt r1, #:upper16:b - a + 65536
b:

@CHECK-NOT: error: Relocation Not In Range
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@efriedma-quic efriedma-quic Nov 14, 2025

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Instead of checking for the error message, please just check that we generate the correct instruction encoding.

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@hwti hwti Nov 14, 2025

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I used arm-movt-movw-range-pass.s as a model.

llvm-mc -show-encoding produces :

        movw    r1, :lower16:((b-a)+65536)      @ encoding: [A,0x10'A',0b0000AAAA,0xe3]
                                        @   fixup A - offset: 0, value: (b-a)+65536, kind: fixup_arm_movw_lo16
        movt    r1, :upper16:((b-a)+65536)      @ encoding: [A,0x10'A',0b0100AAAA,0xe3]
                                        @   fixup A - offset: 0, value: (b-a)+65536, kind: fixup_arm_movt_hi16

so it doesn't show the value is resolved.

Do you want a test with llvm-objdump, like :

@RUN: llvm-mc -triple armv7-eabi -filetype obj %s -o - | llvm-objdump -d --triple armv7-eabi - | FileCheck %s

a:
    movw    r1, #:lower16:b - a + 65536
    movt    r1, #:upper16:b - a + 65536
b:

@CHECK: 0: e3001008 movw r1, #0x8
@CHECK: 4: e3401001 movt r1, #0x1

?

But it actually tests more, so I don't know know if you meant with "just check ...".

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@efriedma-quic efriedma-quic Nov 18, 2025

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Something with llvm-objdump seems fine, yes.

@CHECK-NOT: movw r1, #:lower16:b - a + 65536
@CHECK-NOT: ^
@CHECK-NOT: error: Relocation Not In Range
@CHECK-NOT: movt r1, #:upper16:b - a + 65536
@CHECK-NOT: ^
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