JIT: fix issues with profile incorporation phase (#47723)

Change #47646 did not remove the code in `fgMakeBasicBlocks` that set profile
data. That masked some flaws in `fgIncorporateProfileData`:
* it should process all blocks; nothing has been imported yet
* it must honor a constraint that some handler blocks can't be rare.

This fixes the above, and removes the early profile setting.

src/coreclr/jit/fgbasic.cpp

@@ -2206,35 +2206,6 @@ unsigned Compiler::fgMakeBasicBlocks(const BYTE* codeAddr, IL_OFFSET codeSize, F
         curBBdesc->bbCodeOffs    = curBBoffs;
         curBBdesc->bbCodeOffsEnd = nxtBBoffs;
 
-        BasicBlock::weight_t profileWeight;
-
-        if (fgGetProfileWeightForBasicBlock(curBBoffs, &profileWeight))
-        {
-            if (compIsForInlining())
-            {
-                if (impInlineInfo->profileScaleState == InlineInfo::ProfileScaleState::KNOWN)
-                {
-                    double scaledWeight = impInlineInfo->profileScaleFactor * profileWeight;
-                    profileWeight       = (BasicBlock::weight_t)scaledWeight;
-                }
-            }
-
-            curBBdesc->setBBProfileWeight(profileWeight);
-
-            if (profileWeight == 0)
-            {
-                curBBdesc->bbSetRunRarely();
-            }
-            else
-            {
-                // Note that bbNewBasicBlock (called from fgNewBasicBlock) may have
-                // already marked the block as rarely run.  In that case (and when we know
-                // that the block profile weight is non-zero) we want to unmark that.
-
-                curBBdesc->bbFlags &= ~BBF_RUN_RARELY;
-            }
-        }
-
         switch (jmpKind)
         {
             case BBJ_SWITCH:

src/coreclr/jit/fgprofile.cpp

@@ -932,25 +932,24 @@ PhaseStatus Compiler::fgIncorporateProfileData()
 // Notes:
 //   Count data for inlinees is scaled (usually down).
 //
+//   Since we are now running before the importer, we do not know which
+//   blocks will be imported, and we should not see any internal blocks.
+//
 // Todo:
 //   Normalize counts.
 //
 //   Take advantage of the (likely) correspondence between block order
 //   and schema order?
 //
+//   Find some other mechanism for handling cases where handler entry
+//   blocks must be in the hot section.
+//
 void Compiler::fgIncorporateBlockCounts()
 {
     for (BasicBlock* block = fgFirstBB; block != nullptr; block = block->bbNext)
     {
         BasicBlock::weight_t profileWeight;
 
-        // Skip internal and un-imported blocks.
-        //
-        if ((block->bbFlags & (BBF_INTERNAL | BBF_IMPORTED)) != BBF_IMPORTED)
-        {
-            continue;
-        }
-
         if (fgGetProfileWeightForBasicBlock(block->bbCodeOffs, &profileWeight))
         {
             if (compIsForInlining())
@@ -972,6 +971,16 @@ void Compiler::fgIncorporateBlockCounts()
             {
                 block->bbFlags &= ~BBF_RUN_RARELY;
             }
+
+#if HANDLER_ENTRY_MUST_BE_IN_HOT_SECTION
+            // Handle a special case -- some handler entries can't have zero profile count.
+            //
+            if (this->bbIsHandlerBeg(block) && block->isRunRarely())
+            {
+                JITDUMP("Suppressing zero count for " FMT_BB " as it is a handler entry\n", block->bbNum);
+                block->makeBlockHot();
+            }
+#endif
         }
     }
 }