[AArch64] [Windows] Error out on unsupported symbol locations

These might occur in seemingly generic assembly. Previously when
targeting COFF, they were silently ignored, which certainly won't
give the right result. Instead clearly error out, to make it clear
that the assembly needs to be adjusted for this target.

Also change a preexisting report_fatal_error into a proper error
message, pointing out the offending source instruction. This isn't
strictly an internal error, as it can be triggered by user input.

Differential Revision: https://reviews.llvm.org/D85242

Author: mstorsjo

llvm/lib/Target/AArch64/MCTargetDesc/AArch64WinCOFFObjectWriter.cpp

@@ -11,6 +11,7 @@
 #include "llvm/ADT/Twine.h"
 #include "llvm/BinaryFormat/COFF.h"
 #include "llvm/MC/MCAsmBackend.h"
+#include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCFixup.h"
 #include "llvm/MC/MCFixupKindInfo.h"
@@ -48,10 +49,33 @@ unsigned AArch64WinCOFFObjectWriter::getRelocType(
                                       : Target.getSymA()->getKind();
   const MCExpr *Expr = Fixup.getValue();
 
+  if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
+    AArch64MCExpr::VariantKind RefKind = A64E->getKind();
+    switch (AArch64MCExpr::getSymbolLoc(RefKind)) {
+    case AArch64MCExpr::VK_ABS:
+    case AArch64MCExpr::VK_SECREL:
+      // Supported
+      break;
+    default:
+      Ctx.reportError(Fixup.getLoc(), "relocation variant " +
+                                          A64E->getVariantKindName() +
+                                          " unsupported on COFF targets");
+      return COFF::IMAGE_REL_ARM64_ABSOLUTE; // Dummy return value
+    }
+  }
+
   switch (static_cast<unsigned>(Fixup.getKind())) {
   default: {
-    const MCFixupKindInfo &Info = MAB.getFixupKindInfo(Fixup.getKind());
-    report_fatal_error(Twine("unsupported relocation type: ") + Info.Name);
+    if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
+      Ctx.reportError(Fixup.getLoc(), "relocation type " +
+                                          A64E->getVariantKindName() +
+                                          " unsupported on COFF targets");
+    } else {
+      const MCFixupKindInfo &Info = MAB.getFixupKindInfo(Fixup.getKind());
+      Ctx.reportError(Fixup.getLoc(), Twine("relocation type ") + Info.Name +
+                                          " unsupported on COFF targets");
+    }
+    return COFF::IMAGE_REL_ARM64_ABSOLUTE; // Dummy return value
   }
 
   case FK_Data_4:

llvm/test/MC/AArch64/coff-relocations-diags.s

@@ -0,0 +1,43 @@
+// RUN: not llvm-mc -triple aarch64-win32 -filetype=obj %s -o /dev/null 2>&1 | FileCheck %s
+
+  adrp x0, :got:symbol
+  // CHECK: error: relocation variant :got: unsupported on COFF targets
+  // CHECK-NEXT: adrp x0, :got:symbol
+  // CHECK-NEXT: ^
+
+  ldr x0, [x0, :got_lo12:symbol]
+  // CHECK: error: relocation variant :got_lo12: unsupported on COFF targets
+  // CHECK-NEXT: ldr x0, [x0, :got_lo12:symbol]
+  // CHECK-NEXT: ^
+
+  adrp x0, :tlsdesc:symbol
+  // CHECK: error: relocation variant :tlsdesc: unsupported on COFF targets
+  // CHECK-NEXT: adrp x0, :tlsdesc:symbol
+  // CHECK-NEXT: ^
+  add x0, x0, :tlsdesc_lo12:symbol
+  // CHECK: error: relocation variant :tlsdesc_lo12: unsupported on COFF targets
+  // CHECK-NEXT: add x0, x0, :tlsdesc_lo12:symbol
+  // CHECK-NEXT: ^
+
+  adrp x0, :gottprel:symbol
+  // CHECK: error: relocation variant :gottprel: unsupported on COFF targets
+  // CHECK-NEXT: adrp x0, :gottprel:symbol
+  // CHECK-NEXT: ^
+  ldr x0, [x0, :gottprel_lo12:symbol]
+  // CHECK: error: relocation variant :gottprel_lo12: unsupported on COFF targets
+  // CHECK-NEXT: ldr x0, [x0, :gottprel_lo12:symbol]
+  // CHECK-NEXT: ^
+
+  add x0, x0, #:dtprel_hi12:symbol, lsl #12
+  // CHECK: error: relocation variant :dtprel_hi12: unsupported on COFF targets
+  // CHECK-NEXT: add x0, x0, #:dtprel_hi12:symbol, lsl #12
+  // CHECK-NEXT: ^
+  add x0, x0, :dtprel_lo12:symbol
+  // CHECK: error: relocation variant :dtprel_lo12: unsupported on COFF targets
+  // CHECK-NEXT: add x0, x0, :dtprel_lo12:symbol
+  // CHECK-NEXT: ^
+
+  movz x0, #:abs_g0:symbol
+  // CHECK: error: relocation type :abs_g0: unsupported on COFF targets
+  // CHECK-NEXT: movz x0, #:abs_g0:symbol
+  // CHECK-NEXT: ^