JitSpew.patch

diff --git a/js/src/jit/IonAnalysis.cpp b/js/src/jit/IonAnalysis.cpp
index 543ed0eb8372..e7982b419d74 100644
--- a/js/src/jit/IonAnalysis.cpp
+++ b/js/src/jit/IonAnalysis.cpp
@@ -4012,6 +4012,9 @@ static bool TryEliminateBoundsCheck(BoundsCheckMap& checks, size_t blockIndex,
     return true;
   }
 
+  JitSpew(js::jit::JitSpew_Range, "Trying to eliminate MBoundsCheck: Dominating %d: [%d, %d]; Dominated %d: [%d, %d]\n",
+    dominating->id(), dominating->minimum(), dominating->maximum(), dominated->id(), dominated->minimum(), dominated->maximum());
+
   SimpleLinearSum sumA = ExtractLinearSum(dominating->index());
   SimpleLinearSum sumB = ExtractLinearSum(dominated->index());
 
@@ -4044,6 +4047,9 @@ static bool TryEliminateBoundsCheck(BoundsCheckMap& checks, size_t blockIndex,
   dominating->setMaximum(newMaximum);
   dominating->setBailoutKind(BailoutKind::HoistBoundsCheck);
 
+  JitSpew(js::jit::JitSpew_Range, "Eliminated MBoundsCheck: Dominating %d: [%d, %d]; Dominated %d: [%d, %d]\n",
+    dominating->id(), dominating->minimum(), dominating->maximum(), dominated->id(), dominated->minimum(), dominated->maximum());
+
   return true;
 }
 
diff --git a/js/src/jit/JSONSpewer.cpp b/js/src/jit/JSONSpewer.cpp
index 81ce1a2859ea..db26aadfaa41 100644
--- a/js/src/jit/JSONSpewer.cpp
+++ b/js/src/jit/JSONSpewer.cpp
@@ -69,6 +69,13 @@ void JSONSpewer::spewMDef(MDefinition* def) {
   propertyName("opcode");
   out_.printf("\"");
   def->printOpcode(out_);
+  if (def->isBoundsCheck()) {
+    auto* boundsCheck = def->toBoundsCheck();
+    out_.printf(" #[min, max]: [%d, %d], fallible: %d", boundsCheck->minimum(), boundsCheck->maximum(), boundsCheck->fallible());
+  } else if (def->isBoundsCheckLower()) {
+    auto* boundsCheckLower = def->toBoundsCheckLower();
+    out_.printf(" #[min, max]: [%d, -], fallible: %d", boundsCheckLower->minimum(), boundsCheckLower->fallible());
+  }
   out_.printf("\"");
 
   beginListProperty("attributes");
diff --git a/js/src/jit/RangeAnalysis.cpp b/js/src/jit/RangeAnalysis.cpp
index 25073976121c..8aa6bd68bef7 100644
--- a/js/src/jit/RangeAnalysis.cpp
+++ b/js/src/jit/RangeAnalysis.cpp
@@ -2304,6 +2304,8 @@ static inline bool SymbolicBoundIsValid(MBasicBlock* header, MBoundsCheck* ins,
 
 bool RangeAnalysis::tryHoistBoundsCheck(MBasicBlock* header,
                                         MBoundsCheck* ins) {
+  JitSpew(js::jit::JitSpew_Range, "Try to hoist MBoundsCheck %d: [%d, %d]\n",
+    ins->id(), ins->minimum(), ins->maximum());
   // The bounds check's length must be loop invariant or a constant.
   MDefinition* length = DefinitionOrBetaInputDefinition(ins->length());
   if (length->block()->isMarked() && !length->isConstant()) {
@@ -2378,6 +2380,8 @@ bool RangeAnalysis::tryHoistBoundsCheck(MBasicBlock* header,
   lowerCheck->collectRangeInfoPreTrunc();
   lowerCheck->setBailoutKind(BailoutKind::HoistBoundsCheck);
   preLoop->insertBefore(preLoop->lastIns(), lowerCheck);
+  JitSpew(js::jit::JitSpew_Range, "Hoisted a MBoundsCheckLower %d: [%d, -]\n",
+    lowerCheck->id(), lowerCheck->minimum());
 
   // A common pattern for iterating over typed arrays is this:
   //
@@ -2419,6 +2423,8 @@ bool RangeAnalysis::tryHoistBoundsCheck(MBasicBlock* header,
     upperCheck->collectRangeInfoPreTrunc();
     upperCheck->setBailoutKind(BailoutKind::HoistBoundsCheck);
     preLoop->insertBefore(preLoop->lastIns(), upperCheck);
+    JitSpew(js::jit::JitSpew_Range, "Hoisted a MBoundsCheck %d: [%d, %d]\n",
+      upperCheck->id(), upperCheck->minimum(), upperCheck->maximum());
   }
 
   return true;