Bug 1763099 - Part 6: Remove MBasicBlock::discardDef(). r=jandem,nbp

Both callers to `MBasicBlock::discardDef()` can be changed to call
`MBasicBlock::discard()`.

Depends on D142926

Differential Revision: https://phabricator.services.mozilla.com/D142927

js/src/jit/IonAnalysis.cpp

@@ -3390,15 +3390,15 @@ bool jit::EliminateRedundantChecks(MIRGraph& graph) {
       if (!def->isBoundsCheck()) {
         continue;
       }
+      auto* boundsCheck = def->toBoundsCheck();
 
       bool eliminated = false;
-      if (!TryEliminateBoundsCheck(checks, index, def->toBoundsCheck(),
-                                   &eliminated)) {
+      if (!TryEliminateBoundsCheck(checks, index, boundsCheck, &eliminated)) {
         return false;
       }
 
       if (eliminated) {
-        block->discardDef(def);
+        block->discard(boundsCheck);
       }
     }
     index++;

js/src/jit/MIRGraph.cpp

@@ -670,14 +670,6 @@ void MBasicBlock::discardIgnoreOperands(MInstruction* ins) {
   instructions_.remove(ins);
 }
 
-void MBasicBlock::discardDef(MDefinition* at) {
-  if (at->isPhi()) {
-    at->block()->discardPhi(at->toPhi());
-  } else {
-    at->block()->discard(at->toInstruction());
-  }
-}
-
 void MBasicBlock::discardAllInstructions() {
   MInstructionIterator iter = begin();
   discardAllInstructionsStartingAt(iter);

js/src/jit/MIRGraph.h

@@ -315,7 +315,6 @@ class MBasicBlock : public TempObject, public InlineListNode<MBasicBlock> {
   // Removes an instruction with the intention to discard it.
   void discard(MInstruction* ins);
   void discardLastIns();
-  void discardDef(MDefinition* def);
   void discardAllInstructions();
   void discardAllInstructionsStartingAt(MInstructionIterator iter);
   void discardAllPhis();

js/src/jit/RangeAnalysis.cpp

@@ -367,11 +367,12 @@ bool RangeAnalysis::removeBetaNodes() {
     for (MDefinitionIterator iter(*i); iter;) {
       MDefinition* def = *iter++;
       if (def->isBeta()) {
-        MDefinition* op = def->getOperand(0);
-        JitSpew(JitSpew_Range, "  Removing beta node %u for %u", def->id(),
+        auto* beta = def->toBeta();
+        MDefinition* op = beta->input();
+        JitSpew(JitSpew_Range, "  Removing beta node %u for %u", beta->id(),
                 op->id());
-        def->justReplaceAllUsesWith(op);
-        block->discardDef(def);
+        beta->justReplaceAllUsesWith(op);
+        block->discard(beta);
       } else {
         // We only place Beta nodes at the beginning of basic
         // blocks, so if we see something else, we can move on