[PATCH] D77424: [XCOFF][AIX] Relocation support for SymB

[Digger via Phabricator via llvm-commits]

DiggerLin added inline comments.


================
Comment at: llvm/lib/MC/XCOFFObjectWriter.cpp:462
+  // SymB must be R_NEG here, given the general form of Target(MCValue) is
+  // "SymbolA - SymbolB + imm64".
+  const uint8_t TypeB = XCOFF::RelocationType::R_NEG;
----------------
I have question on the "SymbolA - SymbolB + imm64"

for example: in the assembly of the test case 
```
       .csect .text[PR] 
.foo:
# %bb.0:                                # %entry
        li 4, 0
        cmplwi  3, 3
        stw 3, -8(1)
        stw 4, -12(1)
        bgt     0, LBB0_5
# %bb.1:                                # %entry
        lwz 4, LC0(2)
        slwi 3, 3, 2
        lwzx 3, 3, 4
        add 3, 3, 4
        mtctr 3
        bctr
LBB0_2:                                 # %sw.bb1
        li 3, 1
        b LBB0_6

.......
........
        .csect .rodata[RO]
        .align  2
.LJTI0_0: (symb)
        .long   LBB0_2-.LJTI0_0   

```
the address of LBB0_2 is 44 (0x2C) .


the value in the 
00000058 <.rodata>:
  58:   ff ff ff d4     .long 0xffffffd4   (-0x2C)
                58: R_POS       .text
                58: R_NEG       .rodata-0x58

the jump address 
.text+imm64 (-0x2C) - (0x58) =0x84 + LC0(R2). it not correct

I think the content of in the address of the first bytes .csect .rodata[RO] after link in  should be 
.text - imm64(-0X2C)-(0X58) = -0X2C  + LC0(R2) ?




================
Comment at: llvm/lib/MC/XCOFFObjectWriter.cpp:463
+  // "SymbolA - SymbolB + imm64".
+  const uint8_t TypeB = XCOFF::RelocationType::R_NEG;
+  XCOFFRelocation RelocB = {IndexB, FixupOffsetInCsect, SignAndSize, TypeB};
----------------
what about use  XCOFF::RelocationType type instead of uint8_t ?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D77424/new/

https://reviews.llvm.org/D77424