[PATCH] D88813: [CodeGen] Postprocess PHI nodes for callbr

[Bill Wendling via Phabricator via llvm-commits]

void created this revision.
void added reviewers: nickdesaulniers, jyknight, craig.topper, efriedma.
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When processing PHI nodes after a callbr, we need to make sure that the
PHI nodes on the default branch are resolved after the callbr (inserted
after INLINEASM_BR). The PHI node values on the indirect branches are
processed before the INLINEASM_BR.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D88813

Files:
  llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
  llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h


Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -783,7 +783,8 @@
   void processIntegerCallValue(const Instruction &I,
                                SDValue Value, bool IsSigned);
 
-  void HandlePHINodesInSuccessorBlocks(const BasicBlock *LLVMBB);
+  void HandlePHINodesInSuccessorBlocks(const BasicBlock *LLVMBB,
+                                       bool FirstIter);
 
   void emitInlineAsmError(const CallBase &Call, const Twine &Message);
 
Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1101,6 +1101,7 @@
     CopyToExportRegsIfNeeded(&I);
 
   CurInst = nullptr;
+  ConstantsOut.clear();
 }
 
 void SelectionDAGBuilder::visitPHI(const PHINode &) {
@@ -9994,8 +9995,8 @@
 /// directly add them, because expansion might result in multiple MBB's for one
 /// BB.  As such, the start of the BB might correspond to a different MBB than
 /// the end.
-void
-SelectionDAGBuilder::HandlePHINodesInSuccessorBlocks(const BasicBlock *LLVMBB) {
+void SelectionDAGBuilder::HandlePHINodesInSuccessorBlocks(
+    const BasicBlock *LLVMBB, bool FirstIter) {
   const Instruction *TI = LLVMBB->getTerminator();
 
   SmallPtrSet<MachineBasicBlock *, 4> SuccsHandled;
@@ -10005,6 +10006,21 @@
   for (unsigned succ = 0, e = TI->getNumSuccessors(); succ != e; ++succ) {
     const BasicBlock *SuccBB = TI->getSuccessor(succ);
     if (!isa<PHINode>(SuccBB->begin())) continue;
+
+    if (CI) {
+      if (FirstIter) {
+        // Don't push PHI node values back before an INLINEASM_BR instruction on
+        // the default branch.
+        if (SuccBB == CI->getDefaultDest())
+          continue;
+      } else {
+        // Don't push PHI node values back after an INLINEASM_BR instruction on
+        // the indirect branch.
+        if (SuccBB != CI->getDefaultDest())
+          continue;
+      }
+    }
+
     MachineBasicBlock *SuccMBB = FuncInfo.MBBMap[SuccBB];
 
     // If this terminator has multiple identical successors (common for
@@ -10065,8 +10081,6 @@
       }
     }
   }
-
-  ConstantsOut.clear();
 }
 
 /// Add a successor MBB to ParentMBB< creating a new MachineBB for BB if SuccMBB


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