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f3bb2fa95f
For `ret i64 add (i64 ptrtoint (i32* @foo to i64), i64 1701208431)`,
```
X86DAGToDAGISel::matchAdd
...
// AM.setBaseReg(CurDAG->getRegister(X86::RIP, MVT::i64));
if (!matchAddressRecursively(N.getOperand(0), AM, Depth+1) &&
// Try folding offset but fail; there is a symbolic displacement, so offset cannot be too large
!matchAddressRecursively(Handle.getValue().getOperand(1), AM, Depth+1))
return false;
...
// Try again after commuting the operands.
// AM.Disp = Val; foldOffsetIntoAddress() does not know there will be a symbolic displacement
if (!matchAddressRecursively(Handle.getValue().getOperand(1), AM, Depth+1) &&
// AM.setBaseReg(CurDAG->getRegister(X86::RIP, MVT::i64));
!matchAddressRecursively(Handle.getValue().getOperand(0), AM, Depth+1))
// Succeeded! Produced leaq sym+disp(%rip),...
return false;
```
`foldOffsetIntoAddress()` currently does not know there is a symbolic
displacement and can fold a large offset.
The produced `leaq sym+disp(%rip), %rax` instruction is relocated by
an R_X86_64_PC32. If disp is large and sym+disp-rip>=2**31, there
will be a relocation overflow.
This approach is still not elegant. Unfortunately the isRIPRelative
interface is a bit clumsy. I tried several solutions and eventually
picked this one.
Differential Revision: https://reviews.llvm.org/D73606
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