[AArch64] Diagnose large adrp offset on Windows.

[efriedma]

Summary

On Windows, this relocation can only encode a 21-bit offset. Make sure we emit an error, instead of silently truncating the offset.

Found investigating https://bugs.llvm.org/show_bug.cgi?id=52378

[mstorsjo]

LGTM

llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp

164

Nit: It's not entirely obvious to the reader that these decimal numbers map to the limits of a signed 21 bit number corresponding to the mask below (although that's the main thing one would guess that they mean).

llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp

static uint64_t adjustFixupValue(const MCFixup &Fixup, const MCValue &Target,
   default:
     llvm_unreachable("Unknown fixup kind!");
   case AArch64::fixup_aarch64_pcrel_adr_imm21:
     if (SignedValue > 2097151 || SignedValue < -2097152)
       Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
     return AdrImmBits(Value & 0x1fffffULL);
   case AArch64::fixup_aarch64_pcrel_adrp_imm21:
     assert(!IsResolved);
-    if (TheTriple.isOSBinFormatCOFF())
+    if (TheTriple.isOSBinFormatCOFF()) {
+      if (!isInt<21>(SignedValue))
+        Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
       return AdrImmBits(Value & 0x1fffffULL);
+    }
     return AdrImmBits((Value & 0x1fffff000ULL) >> 12);
   case AArch64::fixup_aarch64_ldr_pcrel_imm19:
   case AArch64::fixup_aarch64_pcrel_branch19:
     // Signed 21-bit immediate
     if (SignedValue > 2097151 || SignedValue < -2097152)
       Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
     if (Value & 0x3)
       Ctx.reportError(Fixup.getLoc(), "fixup not sufficiently aligned");

llvm/test/MC/AArch64/fixup-out-of-range.s

 // RUN: not llvm-mc -triple aarch64--none-eabi -filetype obj < %s -o /dev/null 2>&1 | FileCheck %s
-// RUN: not llvm-mc -triple aarch64-windows -filetype obj < %s -o /dev/null 2>&1 | FileCheck %s
+// RUN: not llvm-mc -triple aarch64-windows -filetype obj < %s -o /dev/null 2>&1 | FileCheck %s -check-prefixes=CHECK,CHECK-WIN
 
 // CHECK: :[[@LINE+1]]:{{[0-9]+}}: error: fixup value out of range
   adr x0, distant
 
 // CHECK: :[[@LINE+1]]:{{[0-9]+}}: error: fixup value out of range
   ldr x0, distant
 
 // CHECK: :[[@LINE+1]]:{{[0-9]+}}: error: fixup not sufficiently aligned
// CHECK: :[[@LINE+1]]:{{[0-9]+}}: error: fixup value out of range
   movz x0, #:abs_g0_s:value1
 
 // CHECK: :[[@LINE+1]]:{{[0-9]+}}: error: fixup value out of range
   movz x0, #:abs_g1_s:value2
 
 // CHECK: :[[@LINE+1]]:{{[0-9]+}}: error: relocation for a thread-local variable points to an absolute symbol
   movz x0, #:tprel_g0:value1
 
+// CHECK-WIN: :[[@LINE+1]]:{{[0-9]+}}: error: fixup value out of range
+  adrp x0, external+0x1000000
 
   .byte 0
 unaligned:
   .byte 0
 
   .space 1<<27
   .balign 8
 distant:
   .word 0
 value1 = 0x12345678
 value2 = 0x123456789