[llvm] [RISCV] When resolving extension implications, handle the default I/E case after implications are resolved. (PR #154353)

[Owen Anderson via llvm-commits]

https://github.com/resistor updated https://github.com/llvm/llvm-project/pull/154353

>From bad4c46451e35d91e1c9d25e92a62295b589ce87 Mon Sep 17 00:00:00 2001
From: Owen Anderson <resistor at mac.com>
Date: Tue, 19 Aug 2025 22:46:47 +0800
Subject: [PATCH] [RISCV] When resolving extension implications, handle the
 default I/E case after implications are resolved.

This is needed to handle the scenario of an extension that implies FeatureStdExtE, as is the case for the
downstream FeatureVendorXCheriot used for Cheriot support.
---
 llvm/lib/TargetParser/RISCVISAInfo.cpp | 28 ++++++++++++++------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/llvm/lib/TargetParser/RISCVISAInfo.cpp b/llvm/lib/TargetParser/RISCVISAInfo.cpp
index d6afb8afd98b4..7617058aa102f 100644
--- a/llvm/lib/TargetParser/RISCVISAInfo.cpp
+++ b/llvm/lib/TargetParser/RISCVISAInfo.cpp
@@ -833,19 +833,6 @@ static bool operator<(StringRef LHS, const ImpliedExtsEntry &RHS) {
 #include "llvm/TargetParser/RISCVTargetParserDef.inc"
 
 void RISCVISAInfo::updateImplication() {
-  bool HasE = Exts.count("e") != 0;
-  bool HasI = Exts.count("i") != 0;
-
-  // If not in e extension and i extension does not exist, i extension is
-  // implied
-  if (!HasE && !HasI) {
-    auto Version = findDefaultVersion("i");
-    Exts["i"] = *Version;
-  }
-
-  if (HasE && HasI)
-    Exts.erase("i");
-
   assert(llvm::is_sorted(ImpliedExts) && "Table not sorted by Name");
 
   // This loop may execute over 1 iteration since implication can be layered
@@ -887,6 +874,21 @@ void RISCVISAInfo::updateImplication() {
     auto Version = findDefaultVersion("zcf");
     Exts["zcf"] = *Version;
   }
+
+  // Handle I/E after implications have been resolved, in case either
+  // of them was implied by another extension.
+  bool HasE = Exts.count("e") != 0;
+  bool HasI = Exts.count("i") != 0;
+
+  // If not in e extension and i extension does not exist, i extension is
+  // implied
+  if (!HasE && !HasI) {
+    auto Version = findDefaultVersion("i");
+    Exts["i"] = *Version;
+  }
+
+  if (HasE && HasI)
+    Exts.erase("i");
 }
 
 static constexpr StringLiteral CombineIntoExts[] = {