[llvm][ARM] Treat xscale arch as an alias of armv5te

[DavidSpickett]

Summary

Previously xscale was known to everything apart
from the ELF streamer so we would crash as soon
as you tried to output an object file.

[DavidSpickett]

For https://github.com/ClangBuiltLinux/linux/issues/1276

I'm not sure if xscale should enable iwmmxt, the best "docs" seem to be the wiki (https://en.wikipedia.org/wiki/XScale). Which says there were some xscale with this feature (v1 or v2 not sure).

There are special arch names for IWMMXT and IWMMXT2 so if the user really wants them they can do so by changing their .arch directive.

[DavidSpickett]

I'm not sure if xscale should enable iwmmxt, the best "docs" seem to be the wiki (https://en.wikipedia.org/wiki/XScale). Which says there were some xscale with this feature (v1 or v2 not sure).

Confirmed that GAS sets the same attributes for xscale so I think what's here is correct.

[DavidSpickett]

Rebase on main.

[nickdesaulniers]

Thanks!

llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp

 //===- lib/MC/ARMELFStreamer.cpp - ELF Object Output for ARM --------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
void ARMTargetELFStreamer::emitArchDefaultAttributes() {
   case ARM::ArchKind::ARMV3:
   case ARM::ArchKind::ARMV3M:
   case ARM::ArchKind::ARMV4:
     setAttributeItem(ARM_ISA_use, Allowed, false);
     break;
 
   case ARM::ArchKind::ARMV4T:
   case ARM::ArchKind::ARMV5T:
+  case ARM::ArchKind::XSCALE:
   case ARM::ArchKind::ARMV5TE:
   case ARM::ArchKind::ARMV6:
     setAttributeItem(ARM_ISA_use, Allowed, false);
     setAttributeItem(THUMB_ISA_use, Allowed, false);
     break;
 
   case ARM::ArchKind::ARMV6T2:
     setAttributeItem(ARM_ISA_use, Allowed, false);

llvm/test/MC/ARM/directive-arch-xscale.s

+@@ Test the .arch directive for xscale
+
+@@ This test case will check the default .ARM.attributes value for the
+@@ xscale architecture.
+
+@ RUN: llvm-mc -triple arm-eabi -filetype asm %s \
+@ RUN:   | FileCheck %s -check-prefix CHECK-ASM
+@ RUN: llvm-mc -triple arm-eabi -filetype obj %s \
+@ RUN:   | llvm-readobj --arch-specific - | FileCheck %s -check-prefix CHECK-ATTR
+
+  .syntax unified
+  .arch xscale
+
+@ CHECK-ASM:  .arch xscale
+
+@ CHECK-ATTR: FileAttributes {
+@ CHECK-ATTR:   Attribute {
+@ CHECK-ATTR:     TagName: CPU_name
+@ CHECK-ATTR:     Value: xscale
+@ CHECK-ATTR:   }
+@ CHECK-ATTR:   Attribute {
+@ CHECK-ATTR:     TagName: CPU_arch
+@ CHECK-ATTR:     Description: ARM v5TE
+@ CHECK-ATTR:   }
+@ CHECK-ATTR:   Attribute {
+@ CHECK-ATTR:     TagName: ARM_ISA_use
+@ CHECK-ATTR:     Description: Permitted
+@ CHECK-ATTR:   }
+@ CHECK-ATTR:   Attribute {
+@ CHECK-ATTR:     TagName: THUMB_ISA_use
+@ CHECK-ATTR:     Description: Thumb-1
+@ CHECK-ATTR:   }
+@ CHECK-ATTR: }
+