[llvm-objdump][AArch64] Fix ADRP target label calculation

[krisb]

Summary

This patch makes ADRP target label address calculations the same as
label address calculations (see AArch64InstPrinter::printAdrpLabel()).

Otherwise the target label looks misleading as ADRP's immediate offset is,
actually, not an offset to this PC, but an offset to the current PC's
page address in pages.

See for example, llvm-objdump/ELF/AArch64/pcrel-address.yaml.
Before this patch the target label <_start+0x80> represents the
address 0x200100 + 0x80 while 0x220000 is expected.

Note that with this patch llvm-objdump output matches GNU objdump.

[MaskRay]

llvm/test/tools/llvm-objdump/ELF/AArch64/pcrel-address.yaml

19

Having the label is an interesting case. Consider adding another case without .data?

[krisb]

llvm/test/tools/llvm-objdump/ELF/AArch64/pcrel-address.yaml

19

Could you please give more details why the case with .data is an interesting one?
If we keep the .data in the example, objdump will not be able to find target label for 0x220000 address since it'll reject .text, considering only .data one, which doesn't contain any symbols.
I'm okay to add another test w/o data, just want to understand what intent was/is under the .data section, if you have some time to give the details.

[krisb]

Rebase & ping

[krisb]

Keep original test case and add another one.

[krisb]

llvm/test/tools/llvm-objdump/ELF/AArch64/pcrel-address.yaml

19

@MaskRay
I added another case where adrp's label points inside .text keeping original one that points inside .data.
But since there are no symbols in .data we do not have target address label calculated for the address from the original case.
Hope, I got you right.

[MaskRay]

llvm/test/tools/llvm-objdump/ELF/AArch64/pcrel-address.yaml

19

Thanks!

llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp

public:
   bool evaluateBranch(const MCInst &Inst, uint64_t Addr, uint64_t Size,
                       uint64_t &Target) const override {
     // Search for a PC-relative argument.
     // This will handle instructions like bcc (where the first argument is the
     // condition code) and cbz (where it is a register).
     const auto &Desc = Info->get(Inst.getOpcode());
     for (unsigned i = 0, e = Inst.getNumOperands(); i != e; i++) {
       if (Desc.OpInfo[i].OperandType == MCOI::OPERAND_PCREL) {
-        int64_t Imm = Inst.getOperand(i).getImm() * 4;
-        Target = Addr + Imm;
+        int64_t Imm = Inst.getOperand(i).getImm();
+        if (Inst.getOpcode() == AArch64::ADRP)
+          Target = (Addr & -4096) + Imm * 4096;
+        else
+          Target = Addr + Imm * 4;
         return true;
       }
     }
     return false;
   }
 
   std::vector<std::pair<uint64_t, uint64_t>>
   findPltEntries(uint64_t PltSectionVA, ArrayRef<uint8_t> PltContents,

llvm/test/tools/llvm-objdump/ELF/AArch64/pcrel-address.yaml

 # RUN: yaml2obj %s -o %t
 # RUN: llvm-objdump %t -d --no-show-raw-insn --no-leading-addr | FileCheck %s
 
 # CHECK-LABEL: <_start>:
-# CHECK-NEXT:    adrp x2, 0x220000 <_start+0x80>
+# CHECK-NEXT:    adrp x2, 0x220000
+# CHECK-NEXT:    adrp x2, 0x201000 <_start+0xf00>
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_EXEC
   Machine: EM_AARCH64
 Sections:
   - Name:    .text
     Type:    SHT_PROGBITS
     Address: 0x200100
     Flags:   [SHF_ALLOC, SHF_EXECINSTR]
-    Content: '02010090'
+    Content: '02010090020000B0'
   - Name:    .data
     Type:    SHT_PROGBITS
     Flags:   [SHF_ALLOC, SHF_WRITE]
     Address: 0x220000
 Symbols:
   - Name:    _start
     Section: .text
     Value:   0x200100