[TableGen][GlobalISel] Use GIM_SwitchOpcode in Combiners

[Pierre-vh]

The call to initOpcodeValuesMap was missing, causing the MatchTable to (unintentionally) not emit a SwitchMatcher. Also adds other code imported from GlobalISelEmitter.cpp to ensure rules are sorted by precedence as well.

Overall this improves GlobalISel compile-time performance by a noticeable amount. See #66751

[llvmbot]

@llvm/pr-subscribers-llvm-globalisel

Changes

The call to initOpcodeValuesMap was missing, causing the MatchTable to (unintentionally) not emit a SwitchMatcher. Also adds other code imported from GlobalISelEmitter.cpp to ensure rules are sorted by precedence as well.

Overall this improves GlobalISel compile-time performance by a noticeable amount. See #66751

---

Full diff: https://github.com/llvm/llvm-project/pull/66864.diff

1 Files Affected:

• (modified) llvm/utils/TableGen/GlobalISelCombinerEmitter.cpp (+13)

diff --git a/llvm/utils/TableGen/GlobalISelCombinerEmitter.cpp b/llvm/utils/TableGen/GlobalISelCombinerEmitter.cpp
index 08a4db2fb3dec91..b28915148ee5169 100644
--- a/llvm/utils/TableGen/GlobalISelCombinerEmitter.cpp
+++ b/llvm/utils/TableGen/GlobalISelCombinerEmitter.cpp
@@ -3652,6 +3652,9 @@ void GICombinerEmitter::gatherRules(
 }
 
 void GICombinerEmitter::run(raw_ostream &OS) {
+  InstructionOpcodeMatcher::initOpcodeValuesMap(Target);
+  LLTOperandMatcher::initTypeIDValuesMap();
+
   Records.startTimer("Gather rules");
   std::vector<RuleMatcher> Rules;
   gatherRules(Rules, Combiner->getValueAsListOfDefs("Rules"));
@@ -3666,6 +3669,16 @@ void GICombinerEmitter::run(raw_ostream &OS) {
   for (const auto &Rule : Rules)
     MaxTemporaries = std::max(MaxTemporaries, Rule.countRendererFns());
 
+  llvm::stable_sort(Rules, [&](const RuleMatcher &A, const RuleMatcher &B) {
+    if (A.isHigherPriorityThan(B)) {
+      assert(!B.isHigherPriorityThan(A) && "Cannot be more important "
+                                           "and less important at "
+                                           "the same time");
+      return true;
+    }
+    return false;
+  });
+
   const MatchTable Table = buildMatchTable(Rules);
 
   Records.startTimer("Emit combiner");

[qcolombet]

Nice catch!

[aemerson]

Thanks for the quick fix, LGTM,