[lld] [LLD][ELF][AArch64] Add support for SHF_AARCH64_PURECODE ELF section flag (3/3) (PR #125689)

[Fangrui Song via llvm-commits]

=?utf-8?q?Csanád_Hajdú?= <csanad.hajdu at arm.com>,
=?utf-8?q?Csanád_Hajdú?= <csanad.hajdu at arm.com>,
=?utf-8?q?Csanád_Hajdú?= <csanad.hajdu at arm.com>,
=?utf-8?q?Csanád_Hajdú?= <csanad.hajdu at arm.com>,
=?utf-8?q?Csanád_Hajdú?= <csanad.hajdu at arm.com>,
=?utf-8?q?Csanád_Hajdú?= <csanad.hajdu at arm.com>,
=?utf-8?q?Csanád_Hajdú?= <csanad.hajdu at arm.com>,
=?utf-8?q?Csanád_Hajdú?= <csanad.hajdu at arm.com>,
=?utf-8?q?Csanád_Hajdú?= <csanad.hajdu at arm.com>,Fangrui Song
 <i at maskray.me>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/125689 at github.com>


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@@ -663,6 +676,33 @@ void AArch64ABSLongThunk::addLongMapSyms() {
   addSymbol("$d", STT_NOTYPE, 8, *tsec);
 }
 
+void AArch64ABSXOLongThunk::writeLong(uint8_t *buf) {
+  const uint8_t data[] = {
+      0x10, 0x00, 0x80, 0xd2, // movz x16, :abs_g0_nc:S, lsl #0
+      0x10, 0x00, 0xa0, 0xf2, // movk x16, :abs_g1_nc:S, lsl #16
+      0x10, 0x00, 0xc0, 0xf2, // movk x16, :abs_g2_nc:S, lsl #32
+      0x10, 0x00, 0xe0, 0xf2, // movk x16, :abs_g3:S,    lsl #48
+      0x00, 0x02, 0x1f, 0xd6, // br   x16
+  };
+  // If mayNeedLandingPad is true then destination is an
+  // AArch64BTILandingPadThunk that defines landingPad.
+  assert(!mayNeedLandingPad || landingPad != nullptr);
+  uint64_t s = mayNeedLandingPad
----------------
MaskRay wrote:

You copied this piece of intricate code. I think we need a test, perhaps a simplified aarch64-thunk-bti.s #108989

Otherwise, it is fairly easy to cause regression here when someone refactors this code.

https://github.com/llvm/llvm-project/pull/125689