[PAC][MC][AArch64] Fix error message for AUTH_ABS64 reloc with ILP32

[kovdan01]

The LP64 eqv: should say that the equivalent is AUTH_ABS64 rather than ABS64 when trying to emit an AUTH absolute reloc with ILP32.

[llvmbot]

@llvm/pr-subscribers-mc

@llvm/pr-subscribers-backend-aarch64

Author: Daniil Kovalev (kovdan01)

Changes

The LP64 eqv: should say that the equivalent is AUTH_ABS64 rather than ABS64 when trying to emit an AUTH absolute reloc with ILP32.

---

Full diff: https://github.com/llvm/llvm-project/pull/89563.diff

2 Files Affected:

• (modified) llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp (+8-8)
• (modified) llvm/test/MC/AArch64/ilp32-diagnostics.s (+8)

diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp
index 6e074b6a63c41d..abbf20257edcc0 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp
@@ -211,18 +211,18 @@ unsigned AArch64ELFObjectWriter::getRelocType(MCContext &Ctx,
               Target.getAccessVariant() == MCSymbolRefExpr::VK_GOTPCREL)
                  ? ELF::R_AARCH64_GOTPCREL32
                  : R_CLS(ABS32);
-    case FK_Data_8:
+    case FK_Data_8: {
+      bool IsAuth = (RefKind == AArch64MCExpr::VK_AUTH ||
+                     RefKind == AArch64MCExpr::VK_AUTHADDR);
       if (IsILP32) {
         Ctx.reportError(Fixup.getLoc(),
-                        "ILP32 8 byte absolute data "
-                        "relocation not supported (LP64 eqv: ABS64)");
+                        Twine("ILP32 8 byte absolute data "
+                              "relocation not supported (LP64 eqv: ") +
+                            (IsAuth ? "AUTH_ABS64" : "ABS64") + Twine(')'));
         return ELF::R_AARCH64_NONE;
-      } else {
-        if (RefKind == AArch64MCExpr::VK_AUTH ||
-            RefKind == AArch64MCExpr::VK_AUTHADDR)
-          return ELF::R_AARCH64_AUTH_ABS64;
-        return ELF::R_AARCH64_ABS64;
       }
+      return (IsAuth ? ELF::R_AARCH64_AUTH_ABS64 : ELF::R_AARCH64_ABS64);
+    }
     case AArch64::fixup_aarch64_add_imm12:
       if (RefKind == AArch64MCExpr::VK_DTPREL_HI12)
         return R_CLS(TLSLD_ADD_DTPREL_HI12);
diff --git a/llvm/test/MC/AArch64/ilp32-diagnostics.s b/llvm/test/MC/AArch64/ilp32-diagnostics.s
index 65c9e4ea5a1c56..4ca15f160418da 100644
--- a/llvm/test/MC/AArch64/ilp32-diagnostics.s
+++ b/llvm/test/MC/AArch64/ilp32-diagnostics.s
@@ -8,6 +8,14 @@
 
         .xword sym+16
 // CHECK-ERROR: error: ILP32 8 byte absolute data relocation not supported (LP64 eqv: ABS64)
+// CHECK-ERROR: ^
+
+        .xword sym@AUTH(da,42)
+// CHECK-ERROR: error: ILP32 8 byte absolute data relocation not supported (LP64 eqv: AUTH_ABS64)
+// CHECK-ERROR: ^
+
+        .xword sym@AUTH(da,42,addr)
+// CHECK-ERROR: error: ILP32 8 byte absolute data relocation not supported (LP64 eqv: AUTH_ABS64)
 // CHECK-ERROR: ^
 
         movz x7, #:abs_g3:some_label

[kovdan01]

AArch64ELFObjectWriter::getRelocType contains many else's after return. If nobody minds, I'll submit a subsequent PR removing use of else after return in this function.

[MaskRay]

8-byte absolute data relocation is not supported in ILP32?

[kovdan01]

According to the spec, it's not - see no "ELF32 code" for R_<CLS>_ABS64 in the table here https://github.com/ARM-software/abi-aa/blob/main/aaelf64/aaelf64.rst#static-data-relocations

[MaskRay]

Ok, I was suggesting a candidate diagnostic message

8-byte absolute data relocation is not supported in ILP32

[kovdan01]

It looks like that error messages across the function use some convention, so it's probably better to stick with it (or change the messages everywhere at once)

[pcc]

Also, I think we should get rid of these LP64 eqv: messages because of the maintenance burden and because they're not really helpful. If you're targeting ILP32 and writing assembly that triggers one of these messages then you're probably an expert who doesn't need help figuring out which relocation type to use, and knowing the LP64 equivalent wouldn't help you anyway because you'd need something that works on ILP32.

[pcc]

#138625