[llvm] Revert "[llvm-exegesis][AArch64] Disable pauth and ldgm as unsupported instructions fixed (#136868)" (PR #142382)

[Tulio Magno Quites Machado Filho via llvm-commits]

https://github.com/tuliom created https://github.com/llvm/llvm-project/pull/142382

This reverts commit 475531b884a1a203af6367df35f1722fe2383e06. But it does not revert the changes from commits
36850a028d149467cafd2702bc0c2587f6b71cce and
5dc3cd0ee40c00d9fb542488fa5a54ff70273112.

>From 1ab848d12b67d6d99b7202a4d3c5b4cf2191dc24 Mon Sep 17 00:00:00 2001
From: Tulio Magno Quites Machado Filho <tuliom at redhat.com>
Date: Fri, 30 May 2025 14:21:14 -0300
Subject: [PATCH] Revert "[llvm-exegesis][AArch64] Disable pauth and ldgm as
 unsupported instructions fixed (#136868)"

This reverts commit 475531b884a1a203af6367df35f1722fe2383e06.
But it does not revert the changes from commits
36850a028d149467cafd2702bc0c2587f6b71cce and
5dc3cd0ee40c00d9fb542488fa5a54ff70273112.
---
 .../AArch64/skip_unsupported_instructions.s   | 14 ----
 .../llvm-exegesis/lib/AArch64/Target.cpp      | 76 -------------------
 2 files changed, 90 deletions(-)
 delete mode 100644 llvm/test/tools/llvm-exegesis/AArch64/skip_unsupported_instructions.s

diff --git a/llvm/test/tools/llvm-exegesis/AArch64/skip_unsupported_instructions.s b/llvm/test/tools/llvm-exegesis/AArch64/skip_unsupported_instructions.s
deleted file mode 100644
index 72009756ed1d5..0000000000000
--- a/llvm/test/tools/llvm-exegesis/AArch64/skip_unsupported_instructions.s
+++ /dev/null
@@ -1,14 +0,0 @@
-llvm/test/tools/llvm-exegesis/AArch64/skip_unsupported_instructions.s
-
-# TODO: This is failing on some systems that have hardware support for
-# pointer authentication. This needs to be fixed before reenabling.
-# REQUIRES: disabled
-
-# REQUIRES: aarch64-registered-target
-
-# Check for skipping of illegal instruction errors (AUT and LDGM)
-# RUN: llvm-exegesis -mcpu=neoverse-v2 -mode=latency --opcode-name=AUTIA --benchmark-phase=assemble-measured-code 2>&1 | FileCheck %s --check-prefix=CHECK-AUTIA
-# CHECK-AUTIA-NOT: snippet crashed while running: Illegal instruction
-
-# RUN: llvm-exegesis -mcpu=neoverse-v2 -mode=latency --opcode-name=LDGM --benchmark-phase=assemble-measured-code 2>&1 | FileCheck %s --check-prefix=CHECK-LDGM
-# CHECK-LDGM: LDGM: Unsupported opcode: load tag multiple
diff --git a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
index a1eb5a46f21fc..d6f4c5220f71d 100644
--- a/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp
@@ -12,12 +12,6 @@
 #if defined(__aarch64__) && defined(__linux__)
 #include <linux/prctl.h> // For PR_PAC_* constants
 #include <sys/prctl.h>
-#ifndef PR_PAC_SET_ENABLED_KEYS
-#define PR_PAC_SET_ENABLED_KEYS 60
-#endif
-#ifndef PR_PAC_GET_ENABLED_KEYS
-#define PR_PAC_GET_ENABLED_KEYS 61
-#endif
 #ifndef PR_PAC_APIAKEY
 #define PR_PAC_APIAKEY (1UL << 0)
 #endif
@@ -38,47 +32,6 @@
 namespace llvm {
 namespace exegesis {
 
-bool isPointerAuth(unsigned Opcode) {
-  switch (Opcode) {
-  default:
-    return false;
-
-  // FIXME: Pointer Authentication instructions.
-  // We would like to measure these instructions, but they can behave
-  // differently on different platforms, and maybe the snippets need to look
-  // different for these instructions,
-  // Platform-specific handling:  On Linux, we disable authentication, may
-  // interfere with measurements. On non-Linux platforms, disable opcodes for
-  // now.
-  case AArch64::AUTDA:
-  case AArch64::AUTDB:
-  case AArch64::AUTDZA:
-  case AArch64::AUTDZB:
-  case AArch64::AUTIA:
-  case AArch64::AUTIA1716:
-  case AArch64::AUTIASP:
-  case AArch64::AUTIAZ:
-  case AArch64::AUTIB:
-  case AArch64::AUTIB1716:
-  case AArch64::AUTIBSP:
-  case AArch64::AUTIBZ:
-  case AArch64::AUTIZA:
-  case AArch64::AUTIZB:
-    return true;
-  }
-}
-
-bool isLoadTagMultiple(unsigned Opcode) {
-  switch (Opcode) {
-  default:
-    return false;
-
-  // Load tag multiple instruction
-  case AArch64::LDGM:
-    return true;
-  }
-}
-
 static unsigned getLoadImmediateOpcode(unsigned RegBitWidth) {
   switch (RegBitWidth) {
   case 32:
@@ -198,35 +151,6 @@ class ExegesisAArch64Target : public ExegesisTarget {
     // Function return is a pseudo-instruction that needs to be expanded
     PM.add(createAArch64ExpandPseudoPass());
   }
-
-  const char *getIgnoredOpcodeReasonOrNull(const LLVMState &State,
-                                           unsigned Opcode) const override {
-    if (const char *Reason =
-            ExegesisTarget::getIgnoredOpcodeReasonOrNull(State, Opcode))
-      return Reason;
-
-    if (isPointerAuth(Opcode)) {
-#if defined(__aarch64__) && defined(__linux__)
-      // Disable all PAC keys. Note that while we expect the measurements to
-      // be the same with PAC keys disabled, they could potentially be lower
-      // since authentication checks are bypassed.
-      if (prctl(PR_PAC_SET_ENABLED_KEYS,
-                PR_PAC_APIAKEY | PR_PAC_APIBKEY | PR_PAC_APDAKEY |
-                    PR_PAC_APDBKEY, // all keys
-                0,                  // disable all
-                0, 0) < 0) {
-        return "Failed to disable PAC keys";
-      }
-#else
-      return "Unsupported opcode: isPointerAuth";
-#endif
-    }
-
-    if (isLoadTagMultiple(Opcode))
-      return "Unsupported opcode: load tag multiple";
-
-    return nullptr;
-  }
 };
 
 } // namespace