JIT: Explicitly set bbFalseTarget in BasicBlock::SetCond (#96406)

src/coreclr/jit/block.cpp

@@ -835,7 +835,8 @@ void BasicBlock::CopyTarget(Compiler* compiler, const BasicBlock* from)
             SetEhf(new (compiler, CMK_BasicBlock) BBehfDesc(compiler, from->GetEhfTargets()));
             break;
         case BBJ_COND:
-            SetCond(from->GetTrueTarget());
+            // TODO-NoFallThrough: Copy false target, too?
+            SetCond(from->GetTrueTarget(), Next());
             break;
         case BBJ_ALWAYS:
             SetKindAndTarget(from->GetKind(), from->GetTarget());
@@ -876,7 +877,8 @@ void BasicBlock::TransferTarget(BasicBlock* from)
             from->bbEhfTargets = nullptr; // Make sure nobody uses the descriptor after this.
             break;
         case BBJ_COND:
-            SetCond(from->GetTrueTarget());
+            // TODO-NoFallThrough: Copy false target, too?
+            SetCond(from->GetTrueTarget(), Next());
             break;
         case BBJ_ALWAYS:
             SetKindAndTarget(from->GetKind(), from->GetTarget());

src/coreclr/jit/block.h

@@ -700,12 +700,14 @@ struct BasicBlock : private LIR::Range
         return (bbFalseTarget == target);
     }
 
-    void SetCond(BasicBlock* trueTarget)
+    void SetCond(BasicBlock* trueTarget, BasicBlock* falseTarget)
     {
         assert(trueTarget != nullptr);
+        // TODO-NoFallThrough: Allow falseTarget to diverge from bbNext
+        assert(falseTarget == bbNext);
         bbKind        = BBJ_COND;
         bbTrueTarget  = trueTarget;
-        bbFalseTarget = bbNext;
+        bbFalseTarget = falseTarget;
     }
 
     // Set both the block kind and target. This can clear `bbTarget` when setting

src/coreclr/jit/fgopt.cpp

@@ -1766,7 +1766,7 @@ PhaseStatus Compiler::fgPostImportationCleanup()
                     GenTree* const jumpIfEntryStateZero = gtNewOperNode(GT_JTRUE, TYP_VOID, compareEntryStateToZero);
                     fgNewStmtAtBeg(fromBlock, jumpIfEntryStateZero);
 
-                    fromBlock->SetCond(toBlock);
+                    fromBlock->SetCond(toBlock, newBlock);
                     fgAddRefPred(toBlock, fromBlock);
                     newBlock->inheritWeight(fromBlock);
 
@@ -2307,12 +2307,12 @@ void Compiler::fgCompactBlocks(BasicBlock* block, BasicBlock* bNext)
             break;
 
         case BBJ_COND:
-            block->SetCond(bNext->GetTrueTarget());
+            block->SetCond(bNext->GetTrueTarget(), bNext->GetFalseTarget());
 
-            /* Update the predecessor list for 'bNext->bbTarget' */
+            /* Update the predecessor list for 'bNext->bbTrueTarget' */
             fgReplacePred(bNext->GetTrueTarget(), bNext, block);
 
-            /* Update the predecessor list for 'bNext->bbFalseTarget' if it is different than 'bNext->bbTarget' */
+            /* Update the predecessor list for 'bNext->bbFalseTarget' if it is different than 'bNext->bbTrueTarget' */
             if (!bNext->TrueTargetIs(bNext->GetFalseTarget()))
             {
                 fgReplacePred(bNext->GetFalseTarget(), bNext, block);
@@ -3295,7 +3295,7 @@ bool Compiler::fgOptimizeSwitchBranches(BasicBlock* block)
             fgSetStmtSeq(switchStmt);
         }
 
-        block->SetCond(block->GetSwitchTargets()->bbsDstTab[0]);
+        block->SetCond(block->GetSwitchTargets()->bbsDstTab[0], block->GetSwitchTargets()->bbsDstTab[1]);
 
         JITDUMP("After:\n");
         DISPNODE(switchTree);
@@ -3710,7 +3710,7 @@ bool Compiler::fgOptimizeUncondBranchToSimpleCond(BasicBlock* block, BasicBlock*
 
     // Fix up block's flow
     //
-    block->SetCond(target->GetTrueTarget());
+    block->SetCond(target->GetTrueTarget(), next);
     fgAddRefPred(block->GetTrueTarget(), block);
     fgRemoveRefPred(target, block);
 
@@ -4117,7 +4117,7 @@ bool Compiler::fgOptimizeBranch(BasicBlock* bJump)
     // We need to update the following flags of the bJump block if they were set in the bDest block
     bJump->CopyFlags(bDest, BBF_COPY_PROPAGATE);
 
-    bJump->SetCond(bDestNormalTarget);
+    bJump->SetCond(bDestNormalTarget, bJump->Next());
 
     /* Update bbRefs and bbPreds */
 
@@ -4277,7 +4277,7 @@ bool Compiler::fgOptimizeSwitchJumps()
 
         // Wire up the new control flow.
         //
-        block->SetCond(dominantTarget);
+        block->SetCond(dominantTarget, newBlock);
         FlowEdge* const blockToTargetEdge   = fgAddRefPred(dominantTarget, block);
         FlowEdge* const blockToNewBlockEdge = newBlock->bbPreds;
         assert(blockToNewBlockEdge->getSourceBlock() == block);
@@ -6205,8 +6205,6 @@ bool Compiler::fgUpdateFlowGraph(bool doTailDuplication, bool isPhase)
                                 fgRemoveRefPred(bDestNext, bDest);
                                 fgAddRefPred(bFixup, bDest);
                                 fgAddRefPred(bDestNext, bFixup);
-
-                                bDest->SetFalseTarget(bDest->Next());
                             }
                         }
                     }

src/coreclr/jit/flowgraph.cpp

@@ -394,7 +394,7 @@ BasicBlock* Compiler::fgCreateGCPoll(GCPollType pollType, BasicBlock* block)
         }
 #endif
 
-        top->SetCond(bottom);
+        top->SetCond(bottom, poll);
         // Bottom has Top and Poll as its predecessors.  Poll has just Top as a predecessor.
         fgAddRefPred(bottom, poll);
         fgAddRefPred(bottom, top);

src/coreclr/jit/indirectcalltransformer.cpp

@@ -278,7 +278,7 @@ class IndirectCallTransformer
 
             // checkBlock
             assert(checkBlock->KindIs(BBJ_ALWAYS));
-            checkBlock->SetCond(elseBlock);
+            checkBlock->SetCond(elseBlock, thenBlock);
             compiler->fgAddRefPred(elseBlock, checkBlock);
             compiler->fgAddRefPred(thenBlock, checkBlock);
 
@@ -591,7 +591,7 @@ class IndirectCallTransformer
                 checkFallsThrough          = false;
 
                 // prevCheckBlock is expected to jump to this new check (if its type check doesn't succeed)
-                prevCheckBlock->SetCond(checkBlock);
+                prevCheckBlock->SetCond(checkBlock, prevCheckBlock->Next());
                 compiler->fgAddRefPred(checkBlock, prevCheckBlock);
 
                 // Calculate the total likelihood for this check as a sum of likelihoods
@@ -1031,7 +1031,7 @@ class IndirectCallTransformer
             // where we know the last check is always true (in case of "exact" GDV)
             if (!checkFallsThrough)
             {
-                checkBlock->SetCond(elseBlock);
+                checkBlock->SetCond(elseBlock, checkBlock->Next());
                 compiler->fgAddRefPred(elseBlock, checkBlock);
             }
             else

src/coreclr/jit/lower.cpp

@@ -965,7 +965,7 @@ GenTree* Lowering::LowerSwitch(GenTree* node)
     // The GT_SWITCH code is still in originalSwitchBB (it will be removed later).
 
     // Turn originalSwitchBB into a BBJ_COND.
-    originalSwitchBB->SetCond(jumpTab[jumpCnt - 1]);
+    originalSwitchBB->SetCond(jumpTab[jumpCnt - 1], afterDefaultCondBlock);
 
     // Fix the pred for the default case: the default block target still has originalSwitchBB
     // as a predecessor, but the fgSplitBlockAfterStatement() moved all predecessors to point
@@ -1101,7 +1101,7 @@ GenTree* Lowering::LowerSwitch(GenTree* node)
             {
                 // Otherwise, it's a conditional branch. Set the branch kind, then add the
                 // condition statement.
-                currentBlock->SetCond(jumpTab[i]);
+                currentBlock->SetCond(jumpTab[i], currentBlock->Next());
 
                 // Now, build the conditional statement for the current case that is
                 // being evaluated:
@@ -1313,15 +1313,15 @@ bool Lowering::TryLowerSwitchToBitTest(
     {
         // GenCondition::C generates JC so we jump to bbCase1 when the bit is set
         bbSwitchCondition = GenCondition::C;
-        bbSwitch->SetCond(bbCase1);
+        bbSwitch->SetCond(bbCase1, bbCase0);
     }
     else
     {
         assert(bbSwitch->NextIs(bbCase1));
 
         // GenCondition::NC generates JNC so we jump to bbCase0 when the bit is not set
         bbSwitchCondition = GenCondition::NC;
-        bbSwitch->SetCond(bbCase0);
+        bbSwitch->SetCond(bbCase0, bbCase1);
     }
 
     comp->fgAddRefPred(bbCase0, bbSwitch);

src/coreclr/jit/morph.cpp

@@ -14910,7 +14910,7 @@ bool Compiler::fgExpandQmarkStmt(BasicBlock* block, Statement* stmt)
 
         thenBlock = fgNewBBafter(BBJ_ALWAYS, condBlock, true, remainderBlock);
         thenBlock->SetFlags(propagateFlagsToAll);
-        condBlock->SetCond(elseBlock);
+        condBlock->SetCond(elseBlock, thenBlock);
         if (!block->HasFlag(BBF_INTERNAL))
         {
             thenBlock->RemoveFlags(BBF_INTERNAL);
@@ -14932,7 +14932,7 @@ bool Compiler::fgExpandQmarkStmt(BasicBlock* block, Statement* stmt)
         //              bbj_cond(true)
         //
         gtReverseCond(condExpr);
-        condBlock->SetCond(remainderBlock);
+        condBlock->SetCond(remainderBlock, elseBlock);
         fgAddRefPred(remainderBlock, condBlock);
         // Since we have no false expr, use the one we'd already created.
         thenBlock = elseBlock;
@@ -14948,7 +14948,7 @@ bool Compiler::fgExpandQmarkStmt(BasicBlock* block, Statement* stmt)
         //              +-->------------+
         //              bbj_cond(true)
         //
-        condBlock->SetCond(remainderBlock);
+        condBlock->SetCond(remainderBlock, elseBlock);
         fgAddRefPred(remainderBlock, condBlock);
 
         elseBlock->inheritWeightPercentage(condBlock, 50);

src/coreclr/jit/patchpoint.cpp

@@ -146,7 +146,7 @@ class PatchpointTransformer
         BasicBlock* helperBlock    = CreateAndInsertBasicBlock(BBJ_ALWAYS, block, block->Next());
 
         // Update flow and flags
-        block->SetCond(remainderBlock);
+        block->SetCond(remainderBlock, helperBlock);
         block->SetFlags(BBF_INTERNAL);
 
         helperBlock->SetFlags(BBF_BACKWARD_JUMP | BBF_NONE_QUIRK);