JIT: revise inlinee scale computations (#51593)

Rework the inlinee profile scale computations so that all scaling happens
during the profile incorporation phase, rather than sometimes deferring
the scaling until inlining. Because of this we no longer need to record
the scale on the inline info.

Toss out profile data if all counts are zero.

Update the edge profile solver to handle a special case where no return block
was executed, but edges within the method had counts. In such cases the entry
block count can end up zero and blocking proper scaling computations. For this
case, try and deduce a plausible count in this case from nearby blocks and edges.

Fix the edge weight computations to tolerate inconsistent data rather than
to assert.

src/coreclr/jit/compiler.h

@@ -5706,7 +5706,7 @@ class Compiler
 
     void WalkSpanningTree(SpanningTreeVisitor* visitor);
     void fgSetProfileWeight(BasicBlock* block, BasicBlock::weight_t weight);
-    void fgComputeProfileScale();
+    void fgApplyProfileScale();
 
     // fgIsUsingProfileWeights - returns true if we have real profile data for this method
     //                           or if we have some fake profile data for the stress mode

src/coreclr/jit/fginline.cpp

@@ -881,8 +881,6 @@ void Compiler::fgInvokeInlineeCompiler(GenTreeCall* call, InlineResult* inlineRe
     inlineInfo.retExprClassHnd        = nullptr;
     inlineInfo.retExprClassHndIsExact = false;
     inlineInfo.inlineResult           = inlineResult;
-    inlineInfo.profileScaleState      = InlineInfo::ProfileScaleState::UNDETERMINED;
-    inlineInfo.profileScaleFactor     = 0.0;
 #ifdef FEATURE_SIMD
     inlineInfo.hasSIMDTypeArgLocalOrReturn = false;
 #endif // FEATURE_SIMD
@@ -1274,10 +1272,6 @@ void Compiler::fgInsertInlineeBlocks(InlineInfo* pInlineInfo)
     //
     // Set the try and handler index and fix the jump types of inlinee's blocks.
     //
-
-    bool inheritWeight;
-    inheritWeight = true; // The firstBB does inherit the weight from the iciBlock
-
     for (block = InlineeCompiler->fgFirstBB; block != nullptr; block = block->bbNext)
     {
         noway_assert(!block->hasTryIndex());
@@ -1299,48 +1293,20 @@ void Compiler::fgInsertInlineeBlocks(InlineInfo* pInlineInfo)
 
         if (block->bbJumpKind == BBJ_RETURN)
         {
-            inheritWeight = true; // A return block does inherit the weight from the iciBlock
             noway_assert((block->bbFlags & BBF_HAS_JMP) == 0);
             if (block->bbNext)
             {
+                JITDUMP("\nConvert bbJumpKind of " FMT_BB " to BBJ_ALWAYS to bottomBlock " FMT_BB "\n", block->bbNum,
+                        bottomBlock->bbNum);
                 block->bbJumpKind = BBJ_ALWAYS;
                 block->bbJumpDest = bottomBlock;
-#ifdef DEBUG
-                if (verbose)
-                {
-                    printf("\nConvert bbJumpKind of " FMT_BB " to BBJ_ALWAYS to bottomBlock " FMT_BB "\n", block->bbNum,
-                           bottomBlock->bbNum);
-                }
-#endif // DEBUG
             }
             else
             {
-#ifdef DEBUG
-                if (verbose)
-                {
-                    printf("\nConvert bbJumpKind of " FMT_BB " to BBJ_NONE\n", block->bbNum);
-                }
-#endif // DEBUG
+                JITDUMP("\nConvert bbJumpKind of " FMT_BB " to BBJ_NONE\n", block->bbNum);
                 block->bbJumpKind = BBJ_NONE;
             }
         }
-
-        // Update profile weight for callee blocks, if we didn't do it already.
-        if (pInlineInfo->profileScaleState == InlineInfo::ProfileScaleState::KNOWN)
-        {
-            continue;
-        }
-
-        // If we were unable to compute a scale for some reason, then
-        // try to do something plausible. Entry/exit blocks match call
-        // site, internal blocks scaled by half; all rare blocks left alone.
-        //
-        if (!block->isRunRarely())
-        {
-            block->inheritWeightPercentage(iciBlock, inheritWeight ? 100 : 50);
-        }
-
-        inheritWeight = false;
     }
 
     // Insert inlinee's blocks into inliner's block list.