[TableGen][GISel] Delete unused Src arguments (NFC)

[s-barannikov]

The last uses were removed in #120332 and #120426.

When emitting renderers, we shouldn't look at the source DAG at all. The required information is provided by the destination DAG and by the instructions referenced in that DAG. Sometimes, we do want to know if a result was referenced in the source DAG; this can be checked by calling RuleMatcher::hasOperand. Any other use of the source DAG when emitting renderers is likely an error.

[llvmbot]

@llvm/pr-subscribers-tablegen

@llvm/pr-subscribers-llvm-globalisel

Author: Sergei Barannikov (s-barannikov)

Changes

The last uses were removed in #120332 and #120426.

When emitting renderers, we shouldn't look at the source DAG at all. The required information is provided by the destination DAG and by the instructions referenced in that DAG. Sometimes, we do want to know if a leaf was referenced in the source DAG; this can be checked by calling RuleMatcher::hasOperand. Any other use of the source DAG when emitting renderers is likely an error.

---

Full diff: https://github.com/llvm/llvm-project/pull/120445.diff

1 Files Affected:

• (modified) llvm/utils/TableGen/GlobalISelEmitter.cpp (+32-32)

diff --git a/llvm/utils/TableGen/GlobalISelEmitter.cpp b/llvm/utils/TableGen/GlobalISelEmitter.cpp
index 715c29c4636aee..59ec991ad2d262 100644
--- a/llvm/utils/TableGen/GlobalISelEmitter.cpp
+++ b/llvm/utils/TableGen/GlobalISelEmitter.cpp
@@ -393,12 +393,13 @@ class GlobalISelEmitter final : public GlobalISelMatchTableExecutorEmitter {
                            bool OperandIsAPointer, bool OperandIsImmArg,
                            unsigned OpIdx, unsigned &TempOpIdx);
 
-  Expected<BuildMIAction &> createAndImportInstructionRenderer(
-      RuleMatcher &M, InstructionMatcher &InsnMatcher,
-      const TreePatternNode &Src, const TreePatternNode &Dst);
+  Expected<BuildMIAction &>
+  createAndImportInstructionRenderer(RuleMatcher &M,
+                                     InstructionMatcher &InsnMatcher,
+                                     const TreePatternNode &Dst);
   Expected<action_iterator> createAndImportSubInstructionRenderer(
       action_iterator InsertPt, RuleMatcher &M, const TreePatternNode &Dst,
-      const TreePatternNode &Src, unsigned TempReg);
+      unsigned TempReg);
   Expected<action_iterator>
   createInstructionRenderer(action_iterator InsertPt, RuleMatcher &M,
                             const TreePatternNode &Dst);
@@ -406,15 +407,16 @@ class GlobalISelEmitter final : public GlobalISelMatchTableExecutorEmitter {
   Expected<action_iterator>
   importExplicitDefRenderers(action_iterator InsertPt, RuleMatcher &M,
                              BuildMIAction &DstMIBuilder,
-                             const TreePatternNode &Src,
                              const TreePatternNode &Dst, unsigned Start = 0);
 
-  Expected<action_iterator> importExplicitUseRenderers(
-      action_iterator InsertPt, RuleMatcher &M, BuildMIAction &DstMIBuilder,
-      const llvm::TreePatternNode &Dst, const TreePatternNode &Src);
-  Expected<action_iterator> importExplicitUseRenderer(
-      action_iterator InsertPt, RuleMatcher &Rule, BuildMIAction &DstMIBuilder,
-      const TreePatternNode &DstChild, const TreePatternNode &Src);
+  Expected<action_iterator>
+  importExplicitUseRenderers(action_iterator InsertPt, RuleMatcher &M,
+                             BuildMIAction &DstMIBuilder,
+                             const TreePatternNode &Dst);
+  Expected<action_iterator>
+  importExplicitUseRenderer(action_iterator InsertPt, RuleMatcher &Rule,
+                            BuildMIAction &DstMIBuilder,
+                            const TreePatternNode &DstChild);
   Error importDefaultOperandRenderers(action_iterator InsertPt, RuleMatcher &M,
                                       BuildMIAction &DstMIBuilder,
                                       const DAGDefaultOperand &DefaultOp) const;
@@ -1196,7 +1198,7 @@ Error GlobalISelEmitter::importChildMatcher(
 
 Expected<action_iterator> GlobalISelEmitter::importExplicitUseRenderer(
     action_iterator InsertPt, RuleMatcher &Rule, BuildMIAction &DstMIBuilder,
-    const TreePatternNode &DstChild, const TreePatternNode &Src) {
+    const TreePatternNode &DstChild) {
 
   const auto &SubOperand = Rule.getComplexSubOperand(DstChild.getName());
   if (SubOperand) {
@@ -1272,7 +1274,7 @@ Expected<action_iterator> GlobalISelEmitter::importExplicitUseRenderer(
       DstMIBuilder.addRenderer<TempRegRenderer>(TempRegID);
 
       auto InsertPtOrError = createAndImportSubInstructionRenderer(
-          ++InsertPt, Rule, DstChild, Src, TempRegID);
+          ++InsertPt, Rule, DstChild, TempRegID);
       if (auto Error = InsertPtOrError.takeError())
         return std::move(Error);
       return InsertPtOrError.get();
@@ -1357,7 +1359,7 @@ Expected<action_iterator> GlobalISelEmitter::importExplicitUseRenderer(
 }
 
 Expected<BuildMIAction &> GlobalISelEmitter::createAndImportInstructionRenderer(
-    RuleMatcher &M, InstructionMatcher &InsnMatcher, const TreePatternNode &Src,
+    RuleMatcher &M, InstructionMatcher &InsnMatcher,
     const TreePatternNode &Dst) {
   auto InsertPtOrError = createInstructionRenderer(M.actions_end(), M, Dst);
   if (auto Error = InsertPtOrError.takeError())
@@ -1377,14 +1379,12 @@ Expected<BuildMIAction &> GlobalISelEmitter::createAndImportInstructionRenderer(
     CopyToPhysRegMIBuilder.addRenderer<CopyPhysRegRenderer>(PhysInput.first);
   }
 
-  if (auto Error =
-          importExplicitDefRenderers(InsertPt, M, DstMIBuilder, Src, Dst)
-              .takeError())
+  if (auto Error = importExplicitDefRenderers(InsertPt, M, DstMIBuilder, Dst)
+                       .takeError())
     return std::move(Error);
 
-  if (auto Error =
-          importExplicitUseRenderers(InsertPt, M, DstMIBuilder, Dst, Src)
-              .takeError())
+  if (auto Error = importExplicitUseRenderers(InsertPt, M, DstMIBuilder, Dst)
+                       .takeError())
     return std::move(Error);
 
   return DstMIBuilder;
@@ -1392,8 +1392,8 @@ Expected<BuildMIAction &> GlobalISelEmitter::createAndImportInstructionRenderer(
 
 Expected<action_iterator>
 GlobalISelEmitter::createAndImportSubInstructionRenderer(
-    const action_iterator InsertPt, RuleMatcher &M, const TreePatternNode &Dst,
-    const TreePatternNode &Src, unsigned TempRegID) {
+    action_iterator InsertPt, RuleMatcher &M, const TreePatternNode &Dst,
+    unsigned TempRegID) {
   auto InsertPtOrError = createInstructionRenderer(InsertPt, M, Dst);
 
   // TODO: Assert there's exactly one result.
@@ -1408,13 +1408,13 @@ GlobalISelEmitter::createAndImportSubInstructionRenderer(
   DstMIBuilder.addRenderer<TempRegRenderer>(TempRegID, true);
 
   // Handle additional (ignored) results.
-  InsertPtOrError = importExplicitDefRenderers(
-      std::prev(*InsertPtOrError), M, DstMIBuilder, Src, Dst, /*Start=*/1);
+  InsertPtOrError = importExplicitDefRenderers(std::prev(*InsertPtOrError), M,
+                                               DstMIBuilder, Dst, /*Start=*/1);
   if (auto Error = InsertPtOrError.takeError())
     return std::move(Error);
 
-  InsertPtOrError = importExplicitUseRenderers(InsertPtOrError.get(), M,
-                                               DstMIBuilder, Dst, Src);
+  InsertPtOrError =
+      importExplicitUseRenderers(InsertPtOrError.get(), M, DstMIBuilder, Dst);
   if (auto Error = InsertPtOrError.takeError())
     return std::move(Error);
 
@@ -1448,7 +1448,7 @@ Expected<action_iterator> GlobalISelEmitter::createInstructionRenderer(
 
 Expected<action_iterator> GlobalISelEmitter::importExplicitDefRenderers(
     action_iterator InsertPt, RuleMatcher &M, BuildMIAction &DstMIBuilder,
-    const TreePatternNode &Src, const TreePatternNode &Dst, unsigned Start) {
+    const TreePatternNode &Dst, unsigned Start) {
   const CodeGenInstruction *DstI = DstMIBuilder.getCGI();
 
   // Some instructions have multiple defs, but are missing a type entry
@@ -1497,7 +1497,7 @@ Expected<action_iterator> GlobalISelEmitter::importExplicitDefRenderers(
 
 Expected<action_iterator> GlobalISelEmitter::importExplicitUseRenderers(
     action_iterator InsertPt, RuleMatcher &M, BuildMIAction &DstMIBuilder,
-    const llvm::TreePatternNode &Dst, const llvm::TreePatternNode &Src) {
+    const TreePatternNode &Dst) {
   const CodeGenInstruction *DstI = DstMIBuilder.getCGI();
   CodeGenInstruction *OrigDstI = &Target.getInstruction(Dst.getOperator());
 
@@ -1527,7 +1527,7 @@ Expected<action_iterator> GlobalISelEmitter::importExplicitUseRenderers(
                                                         TempRegID);
 
       auto InsertPtOrError = createAndImportSubInstructionRenderer(
-          ++InsertPt, M, ValChild, Src, TempRegID);
+          ++InsertPt, M, ValChild, TempRegID);
       if (auto Error = InsertPtOrError.takeError())
         return std::move(Error);
 
@@ -1585,7 +1585,7 @@ Expected<action_iterator> GlobalISelEmitter::importExplicitUseRenderers(
         CodeGenSubRegIndex *SubIdx = CGRegs.getSubRegIdx(SubRegInit->getDef());
 
         auto InsertPtOrError =
-            importExplicitUseRenderer(InsertPt, M, DstMIBuilder, ValChild, Src);
+            importExplicitUseRenderer(InsertPt, M, DstMIBuilder, ValChild);
         if (auto Error = InsertPtOrError.takeError())
           return std::move(Error);
         InsertPt = InsertPtOrError.get();
@@ -1654,7 +1654,7 @@ Expected<action_iterator> GlobalISelEmitter::importExplicitUseRenderers(
     }
 
     auto InsertPtOrError = importExplicitUseRenderer(InsertPt, M, DstMIBuilder,
-                                                     Dst.getChild(Child), Src);
+                                                     Dst.getChild(Child));
     if (auto Error = InsertPtOrError.takeError())
       return std::move(Error);
     InsertPt = InsertPtOrError.get();
@@ -2135,7 +2135,7 @@ Expected<RuleMatcher> GlobalISelEmitter::runOnPattern(const PatternToMatch &P) {
   }
 
   auto DstMIBuilderOrError =
-      createAndImportInstructionRenderer(M, InsnMatcher, Src, Dst);
+      createAndImportInstructionRenderer(M, InsnMatcher, Dst);
   if (auto Error = DstMIBuilderOrError.takeError())
     return std::move(Error);
   BuildMIAction &DstMIBuilder = DstMIBuilderOrError.get();

[arsenm]

Sometimes, we do want to know if a leaf was referenced in the source DAG; this can be checked by calling RuleMatcher::hasOperand

Probably should document this rule somewhere

[s-barannikov]

Probably should document this rule somewhere

I was thinking about writing some developer documentation on these two backends (GISel / SDAGISel). I find it very difficult to understand how they work, let alone make changes to them. Given my level of English, it will take a little less than eternity though.
I'll try to document at least something.