On Dec 3, 2010, at 11:40 AM, Jason W Kim wrote:
> Author: jasonwkim
> Date: Fri Dec 3 13:40:23 2010
> New Revision: 120832
>
> URL: http://llvm.org/viewvc/llvm-project?rev=120832&view=rev
> Log:
> fix ARM::fixup_arm_branch, cleanup, and share more code between ELF and Darwin
>
> Modified:
> llvm/trunk/lib/Target/ARM/ARMAsmBackend.cpp
>
> Modified: llvm/trunk/lib/Target/ARM/ARMAsmBackend.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMAsmBackend.cpp?rev=120832&r1=120831&r2=120832&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Target/ARM/ARMAsmBackend.cpp (original)
> +++ llvm/trunk/lib/Target/ARM/ARMAsmBackend.cpp Fri Dec 3 13:40:23 2010
> @@ -65,9 +65,16 @@
> default:
> llvm_unreachable("Unknown fixup kind!");
> case FK_Data_4:
> + return Value;
> case ARM::fixup_arm_movt_hi16:
> - case ARM::fixup_arm_movw_lo16:
> + case ARM::fixup_arm_movw_lo16: {
> + unsigned Hi4 = (Value & 0xF000) >> 12;
> + unsigned Lo12 = Value & 0x0FFF;
> + // inst{19-16} = Hi4;
> + // inst{11-0} = Lo12;
> + Value = (Hi4 << 16) | (Lo12);
> return Value;
> + }
> case ARM::fixup_arm_ldst_pcrel_12: {
> bool isAdd = true;
> // ARM PC-relative values are offset by 8.
> @@ -96,7 +103,7 @@
> case ARM::fixup_arm_branch:
> // These values don't encode the low two bits since they're always zero.
> // Offset by 8 just as above.
> - return (Value - 8) >> 2;
> + return 0xFFFFFF & ((Value - 8) >> 2);
Why do we need to mask here? If the value doesn't fit in the range, that's an error, right? We should just assert, I think.
Likewise for the MOVW/MOVT values.
> case ARM::fixup_arm_pcrel_10: {
> // Offset by 8 just as above.
> Value = Value - 8;
> @@ -142,7 +149,7 @@
> }
> };
>
> -// Fixme: can we raise this to share code between Darwin and ELF?
> +// Fixme: Raise this to share code between Darwin and ELF.
> void ELFARMAsmBackend::ApplyFixup(const MCFixup &Fixup, MCDataFragment &DF,
> uint64_t Value) const {
> uint32_t Mask = 0;
> @@ -150,32 +157,12 @@
> unsigned NumBytes = 4;
> Value = adjustFixupValue(Fixup.getKind(), Value);
>
> - switch (Fixup.getKind()) {
> - default: assert(0 && "Unsupported Fixup kind"); break;
> - case ARM::fixup_arm_branch: {
> - unsigned Lo24 = Value & 0xFFFFFF;
> - Mask = ~(0xFFFFFF);
> - Value = Lo24;
> - }; break;
> - case ARM::fixup_arm_movt_hi16:
> - case ARM::fixup_arm_movw_lo16: {
> - unsigned Hi4 = (Value & 0xF000) >> 12;
> - unsigned Lo12 = Value & 0x0FFF;
> - // inst{19-16} = Hi4;
> - // inst{11-0} = Lo12;
> - Value = (Hi4 << 16) | (Lo12);
> - Mask = ~(0xF0FFF);
> - }; break;
> - }
> -
> assert((Fixup.getOffset() % NumBytes == 0)
> && "Offset mod NumBytes is nonzero!");
> // For each byte of the fragment that the fixup touches, mask in the
> // bits from the fixup value.
> // The Value has been "split up" into the appropriate bitfields above.
> - // Fixme: how to share code with the .td generated code?
> for (unsigned i = 0; i != NumBytes; ++i) {
> - DF.getContents()[Fixup.getOffset() + i] &= uint8_t(Mask >> (i * 8));
> DF.getContents()[Fixup.getOffset() + i] |= uint8_t(Value >> (i * 8));
> }
> }
>
>
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