[WIP] Alternative approach to issue 47202

src/coreclr/jit/codegencommon.cpp

@@ -6959,8 +6959,11 @@ void CodeGen::genSetScopeInfoUsingVariableRanges()
                 end++;
             }
 
-            genSetScopeInfo(liveRangeIndex, start, end - start, varNum, varNum, true, loc);
-            liveRangeIndex++;
+            if (start < end)
+            {
+                genSetScopeInfo(liveRangeIndex, start, end - start, varNum, varNum, true, loc);
+                liveRangeIndex++;
+            }
         };
 
         siVarLoc*      curLoc   = nullptr;

src/coreclr/jit/compiler.h

@@ -7718,7 +7718,12 @@ class Compiler
         UNATIVE_OFFSET             endOffset;
         DWORD                      varNumber;
         CodeGenInterface::siVarLoc loc;
-    } * eeVars;
+    };
+    // We use a temporary buffer to copy all variable debug info,
+    // and once we know exactly the amount of info to report,
+    // we ask the vm for memory and copy it.
+    VarResultInfo* eeJitTempVars; // temporary buffer
+    VarResultInfo* eeVars;
     void eeSetLVcount(unsigned count);
     void eeSetLVinfo(unsigned                          which,
                      UNATIVE_OFFSET                    startOffs,

src/coreclr/jit/ee_il_dll.cpp

@@ -646,16 +646,16 @@ void Compiler::eeSetLVcount(unsigned count)
 {
     assert(opts.compScopeInfo);
 
-    JITDUMP("VarLocInfo count is %d\n", count);
+    JITDUMP("VarLocInfo estimated count is %d\n", count);
 
     eeVarsCount = count;
     if (eeVarsCount)
     {
-        eeVars = (VarResultInfo*)info.compCompHnd->allocateArray(eeVarsCount * sizeof(eeVars[0]));
+        eeJitTempVars = new (this, CMK_DebugInfo) VarResultInfo[count];
     }
     else
     {
-        eeVars = nullptr;
+        eeJitTempVars = nullptr;
     }
 }
 
@@ -672,12 +672,12 @@ void Compiler::eeSetLVinfo(unsigned                          which,
     assert(eeVarsCount > 0);
     assert(which < eeVarsCount);
 
-    if (eeVars != nullptr)
+    if (eeJitTempVars != nullptr)
     {
-        eeVars[which].startOffset = startOffs;
-        eeVars[which].endOffset   = startOffs + length;
-        eeVars[which].varNumber   = varNum;
-        eeVars[which].loc         = varLoc;
+        eeJitTempVars[which].startOffset = startOffs;
+        eeJitTempVars[which].endOffset   = startOffs + length;
+        eeJitTempVars[which].varNumber   = varNum;
+        eeJitTempVars[which].loc         = varLoc;
     }
 }
 
@@ -687,6 +687,17 @@ void Compiler::eeSetLVdone()
     assert(sizeof(eeVars[0]) == sizeof(ICorDebugInfo::NativeVarInfo));
     assert(opts.compScopeInfo);
 
+    if (eeVarsCount)
+    {
+        // Ask the vm for memory and copy the pre-calculated VarResultInfo into it
+        eeVars = (VarResultInfo*)info.compCompHnd->allocateArray(eeVarsCount * sizeof(eeVars[0]));
+        memcpy(eeVars, eeJitTempVars, eeVarsCount * sizeof(eeVars[0]));
+    }
+    else
+    {
+        eeVars = nullptr;
+    }
+
 #ifdef DEBUG
     if (verbose || opts.dspDebugInfo)
     {