https://github.com/atrosinenko created 
https://github.com/llvm/llvm-project/pull/79311

Core LLVM has AArch64TargetParser.h header describing the mapping from Armv8.x 
and Armv9.x architecture extensions to the particular list of features that are 
mandatory for the extension.

Clang partially reimplements this in AArch64TargetInfo::setArchFeatures() 
function. This patch simplifies setArchFeatures() by dropping obvious cases of 
duplication, though it seems not all the dependencies are listed in 
AArch64TargetParser.h yet.

Specifically, this patch drops `HasX = true` statements for the following 
features:
* v8.1-a: CRC, LSE, RDM
* v8.3-a: RCPC, NeonMode (it is enabled by the base Armv8-a and indirectly by 
-target-feature +fcma)
* v8.4-a: DOTPROD
* v8.6-a: BF16, MATMUL

In Clang's AArch64TargetInfo::handleTargetFeatures() function, the string 
literal "+jscvt" is changed to "+jsconv" and "+cccp" to "+ccpp", so the 
information is conveyed from TargetParser.

Additionally, this patch makes __ARM_FEATURE_BTI and __ARM_FEATURE_JCVT 
conditional on the particular HasX flags instead of an architecture extension 
as a whole, as using TargetParser makes it possible to specify the requested 
architecture like "armv8.5+nojscvt".

>From e0d278d9fcdd01f574bbf5fa1bcbbaf7875525de Mon Sep 17 00:00:00 2001
From: Anatoly Trosinenko <atrosine...@accesssoftek.com>
Date: Tue, 23 Jan 2024 12:40:00 +0300
Subject: [PATCH] [AArch64] Simplify Clang's description of architecture
 extensions

Core LLVM has AArch64TargetParser.h header describing the mapping from
Armv8.x and Armv9.x architecture extensions to the particular list of
features that are mandatory for the extension.

Clang partially reimplements this in AArch64TargetInfo::setArchFeatures()
function. This patch simplifies setArchFeatures() by dropping obvious
cases of duplication, though it seems not all the dependencies are
listed in AArch64TargetParser.h yet.

Specifically, this patch drops `HasX = true` statements for the
following features:
* v8.1-a: CRC, LSE, RDM
* v8.3-a: RCPC, NeonMode (it is enabled by the base Armv8-a and
  indirectly by -target-feature +fcma)
* v8.4-a: DOTPROD
* v8.6-a: BF16, MATMUL

In Clang's AArch64TargetInfo::handleTargetFeatures() function, the
string literal "+jscvt" is changed to "+jsconv" and "+cccp" to "+ccpp",
so the information is conveyed from TargetParser.

Additionally, this patch makes __ARM_FEATURE_BTI and __ARM_FEATURE_JCVT
conditional on the particular HasX flags instead of an architecture
extension as a whole, as using TargetParser makes it possible to specify
the requested architecture like "armv8.5+nojscvt".
---
 clang/lib/Basic/Targets/AArch64.cpp | 48 +++++++++--------------------
 1 file changed, 15 insertions(+), 33 deletions(-)

diff --git a/clang/lib/Basic/Targets/AArch64.cpp 
b/clang/lib/Basic/Targets/AArch64.cpp
index d47181bfca4fc86..0ac890551fadb24 100644
--- a/clang/lib/Basic/Targets/AArch64.cpp
+++ b/clang/lib/Basic/Targets/AArch64.cpp
@@ -55,24 +55,19 @@ static constexpr Builtin::Info BuiltinInfo[] = {
 };
 
 void AArch64TargetInfo::setArchFeatures() {
+  // FIXME Could we drop this function altogether and migrate everything
+  //       to AArch64TargetParser in LLVM core?
   if (*ArchInfo == llvm::AArch64::ARMV8R) {
-    HasDotProd = true;
     HasDIT = true;
     HasFlagM = true;
-    HasRCPC = true;
     FPU |= NeonMode;
     HasCCPP = true;
-    HasCRC = true;
     HasLSE = true;
-    HasRDM = true;
   } else if (ArchInfo->Version.getMajor() == 8) {
     if (ArchInfo->Version.getMinor() >= 7u) {
       HasWFxT = true;
     }
-    if (ArchInfo->Version.getMinor() >= 6u) {
-      HasBFloat16 = true;
-      HasMatMul = true;
-    }
+    // No special cases for Armv8.6-a
     if (ArchInfo->Version.getMinor() >= 5u) {
       HasAlternativeNZCV = true;
       HasFRInt3264 = true;
@@ -82,30 +77,19 @@ void AArch64TargetInfo::setArchFeatures() {
       HasBTI = true;
     }
     if (ArchInfo->Version.getMinor() >= 4u) {
-      HasDotProd = true;
       HasDIT = true;
       HasFlagM = true;
     }
-    if (ArchInfo->Version.getMinor() >= 3u) {
-      HasRCPC = true;
-      FPU |= NeonMode;
-    }
+    // No special cases for Armv8.3-a
     if (ArchInfo->Version.getMinor() >= 2u) {
       HasCCPP = true;
     }
-    if (ArchInfo->Version.getMinor() >= 1u) {
-      HasCRC = true;
-      HasLSE = true;
-      HasRDM = true;
-    }
+    // No special cases for Armv8.1-a
   } else if (ArchInfo->Version.getMajor() == 9) {
     if (ArchInfo->Version.getMinor() >= 2u) {
       HasWFxT = true;
     }
-    if (ArchInfo->Version.getMinor() >= 1u) {
-      HasBFloat16 = true;
-      HasMatMul = true;
-    }
+    // No special cases for Armv9.1-a
     FPU |= SveMode;
     HasSVE2 = true;
     HasFullFP16 = true;
@@ -115,15 +99,9 @@ void AArch64TargetInfo::setArchFeatures() {
     HasSB = true;
     HasPredRes = true;
     HasBTI = true;
-    HasDotProd = true;
     HasDIT = true;
     HasFlagM = true;
-    HasRCPC = true;
-    FPU |= NeonMode;
     HasCCPP = true;
-    HasCRC = true;
-    HasLSE = true;
-    HasRDM = true;
   }
 }
 
@@ -257,7 +235,6 @@ void AArch64TargetInfo::getTargetDefinesARMV82A(const 
LangOptions &Opts,
 void AArch64TargetInfo::getTargetDefinesARMV83A(const LangOptions &Opts,
                                                 MacroBuilder &Builder) const {
   Builder.defineMacro("__ARM_FEATURE_COMPLEX", "1");
-  Builder.defineMacro("__ARM_FEATURE_JCVT", "1");
   Builder.defineMacro("__ARM_FEATURE_PAUTH", "1");
   // Also include the Armv8.2 defines
   getTargetDefinesARMV82A(Opts, Builder);
@@ -272,7 +249,6 @@ void AArch64TargetInfo::getTargetDefinesARMV84A(const 
LangOptions &Opts,
 void AArch64TargetInfo::getTargetDefinesARMV85A(const LangOptions &Opts,
                                                 MacroBuilder &Builder) const {
   Builder.defineMacro("__ARM_FEATURE_FRINT", "1");
-  Builder.defineMacro("__ARM_FEATURE_BTI", "1");
   // Also include the Armv8.4 defines
   getTargetDefinesARMV84A(Opts, Builder);
 }
@@ -472,7 +448,10 @@ void AArch64TargetInfo::getTargetDefines(const LangOptions 
&Opts,
   if ((FPU & NeonMode) && HasFullFP16)
     Builder.defineMacro("__ARM_FEATURE_FP16_VECTOR_ARITHMETIC", "1");
   if (HasFullFP16)
-   Builder.defineMacro("__ARM_FEATURE_FP16_SCALAR_ARITHMETIC", "1");
+    Builder.defineMacro("__ARM_FEATURE_FP16_SCALAR_ARITHMETIC", "1");
+
+  if (HasJSCVT)
+    Builder.defineMacro("__ARM_FEATURE_JCVT", "1");
 
   if (HasDotProd)
     Builder.defineMacro("__ARM_FEATURE_DOTPROD", "1");
@@ -530,6 +509,9 @@ void AArch64TargetInfo::getTargetDefines(const LangOptions 
&Opts,
     Builder.defineMacro("__ARM_FEATURE_PAC_DEFAULT", std::to_string(Value));
   }
 
+  if (HasBTI)
+    Builder.defineMacro("__ARM_FEATURE_BTI", "1");
+
   if (Opts.BranchTargetEnforcement)
     Builder.defineMacro("__ARM_FEATURE_BTI_DEFAULT", "1");
 
@@ -741,7 +723,7 @@ bool 
AArch64TargetInfo::handleTargetFeatures(std::vector<std::string> &Features,
 
     if (Feature == "+neon" || Feature == "+fp-armv8")
       FPU |= NeonMode;
-    if (Feature == "+jscvt") {
+    if (Feature == "+jsconv") {
       HasJSCVT = true;
       FPU |= NeonMode;
     }
@@ -860,7 +842,7 @@ bool 
AArch64TargetInfo::handleTargetFeatures(std::vector<std::string> &Features,
     }
     if (Feature == "+dit")
       HasDIT = true;
-    if (Feature == "+cccp")
+    if (Feature == "+ccpp")
       HasCCPP = true;
     if (Feature == "+ccdp") {
       HasCCPP = true;

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