[clang] [Clang][AArch64] Fix typo with colon-separated syntax for system registers (PR #105608)

[via cfe-commits]

https://github.com/v01dXYZ updated https://github.com/llvm/llvm-project/pull/105608

>From faef073dab6d45f1b50fc877e5cf336a3427ecfa Mon Sep 17 00:00:00 2001
From: v01dxyz <v01dxyz at v01d.xyz>
Date: Thu, 22 Aug 2024 03:55:27 +0200
Subject: [PATCH] [Clang][AArch64] Fix typo with colon-separated syntax for
 system registers

The range for Op0 was set to 1 instead of 3. Since the ranges are all
power of 2 minus 1, this commit reformulates them with the bitwidth of
each part of the register to highlight the association with the
encoding.

cf one commit description explaining the encoding of an
implementation-defined system register:

e493f177eeee84a9c6000ca7c92499233490f1d1
---
 clang/lib/Sema/SemaARM.cpp                 | 8 ++++----
 clang/test/Sema/aarch64-special-register.c | 7 +++++++
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/clang/lib/Sema/SemaARM.cpp b/clang/lib/Sema/SemaARM.cpp
index d8dd4fe16e3af0..cb53c61aa857d7 100644
--- a/clang/lib/Sema/SemaARM.cpp
+++ b/clang/lib/Sema/SemaARM.cpp
@@ -248,16 +248,16 @@ bool SemaARM::BuiltinARMSpecialReg(unsigned BuiltinID, CallExpr *TheCall,
       }
     }
 
-    SmallVector<int, 5> Ranges;
+    SmallVector<int, 5> FieldBitWidths;
     if (FiveFields)
-      Ranges.append({IsAArch64Builtin ? 1 : 15, 7, 15, 15, 7});
+      FieldBitWidths.append({IsAArch64Builtin ? 2 : 4, 3, 4, 4, 3});
     else
-      Ranges.append({15, 7, 15});
+      FieldBitWidths.append({4, 3, 4});
 
     for (unsigned i = 0; i < Fields.size(); ++i) {
       int IntField;
       ValidString &= !Fields[i].getAsInteger(10, IntField);
-      ValidString &= (IntField >= 0 && IntField <= Ranges[i]);
+      ValidString &= (IntField >= 0 && IntField < (1 << FieldBitWidths[i]));
     }
 
     if (!ValidString)
diff --git a/clang/test/Sema/aarch64-special-register.c b/clang/test/Sema/aarch64-special-register.c
index 4d2cfd8b37c847..937c1eaf6b6565 100644
--- a/clang/test/Sema/aarch64-special-register.c
+++ b/clang/test/Sema/aarch64-special-register.c
@@ -116,6 +116,13 @@ unsigned long rsr64_6(void) {
   return __builtin_arm_rsr64("0:1:16:16:2"); //expected-error {{invalid special register for builtin}}
 }
 
+void rsr64_7(unsigned long *r) {
+  // The following three instructions should produce the same assembly.
+  r[0] = __builtin_arm_rsr64("ICC_CTLR_EL3");
+  r[1] = __builtin_arm_rsr64("s3_6_c12_c12_4");
+  r[2] = __builtin_arm_rsr64("3:6:12:12:4");
+}
+
 __uint128_t rsr128_3(void) {
   return __builtin_arm_rsr128("0:1:2"); //expected-error {{invalid special register for builtin}}
 }