[PATCH] D143219: [llvm][TailDuplicator] permit taildup'ing pred MBB containing INLINEASM_BR

[Nick Desaulniers via Phabricator via llvm-commits]

nickdesaulniers created this revision.
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If we have:
bb0:

  INLINEASM_BR ...
  b bb2

bb1:

  ...

bb2:

  ret

it would be nice to taildup that ret into bb0.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D143219

Files:
  llvm/lib/CodeGen/TailDuplicator.cpp
  llvm/test/CodeGen/X86/callbr-asm-sink.ll
  llvm/test/CodeGen/X86/callbr-asm.ll
  llvm/test/CodeGen/X86/inline-asm-pic.ll


Index: llvm/test/CodeGen/X86/inline-asm-pic.ll
===================================================================
--- llvm/test/CodeGen/X86/inline-asm-pic.ll
+++ llvm/test/CodeGen/X86/inline-asm-pic.ll
@@ -29,7 +29,6 @@
 ; CHECK-NEXT:    ## LBB1_1
 ; CHECK-EMPTY:
 ; CHECK-NEXT:    ## InlineAsm End
-; CHECK-NEXT:  ## %bb.2: ## %return
 ; CHECK-NEXT:    retl
 ; CHECK-NEXT:  Ltmp0: ## Block address taken
 ; CHECK-NEXT:  LBB1_1: ## %overflow
Index: llvm/test/CodeGen/X86/callbr-asm.ll
===================================================================
--- llvm/test/CodeGen/X86/callbr-asm.ll
+++ llvm/test/CodeGen/X86/callbr-asm.ll
@@ -171,13 +171,14 @@
 ; CHECK-LABEL: test4:
 ; CHECK:       # %bb.0: # %entry
 ; CHECK-NEXT:    #APP
-; CHECK-NEXT:    ja .LBB4_3
+; CHECK-NEXT:    ja .LBB4_2
 ; CHECK-NEXT:    #NO_APP
 ; CHECK-NEXT:  # %bb.1: # %asm.fallthrough
 ; CHECK-NEXT:    #APP
-; CHECK-NEXT:    ja .LBB4_3
+; CHECK-NEXT:    ja .LBB4_2
 ; CHECK-NEXT:    #NO_APP
-; CHECK-NEXT:  .LBB4_3: # Block address taken
+; CHECK-NEXT:    retl
+; CHECK-NEXT:  .LBB4_2: # Block address taken
 ; CHECK-NEXT:    # %quux
 ; CHECK-NEXT:    # Label of block must be emitted
 ; CHECK-NEXT:    retl
Index: llvm/test/CodeGen/X86/callbr-asm-sink.ll
===================================================================
--- llvm/test/CodeGen/X86/callbr-asm-sink.ll
+++ llvm/test/CodeGen/X86/callbr-asm-sink.ll
@@ -14,7 +14,6 @@
 ; CHECK-NEXT:    #APP
 ; CHECK-NEXT:    # 8(%rdi) .LBB0_1
 ; CHECK-NEXT:    #NO_APP
-; CHECK-NEXT:  # %bb.2:
 ; CHECK-NEXT:    retq
 ; CHECK-NEXT:  .LBB0_1: # Block address taken
 ; CHECK-NEXT:    # Label of block must be emitted
Index: llvm/lib/CodeGen/TailDuplicator.cpp
===================================================================
--- llvm/lib/CodeGen/TailDuplicator.cpp
+++ llvm/lib/CodeGen/TailDuplicator.cpp
@@ -791,7 +791,7 @@
 bool TailDuplicator::canTailDuplicate(MachineBasicBlock *TailBB,
                                       MachineBasicBlock *PredBB) {
   // EH edges are ignored by analyzeBranch.
-  if (PredBB->succ_size() > 1)
+  if (PredBB->succ_size() > 1 && !PredBB->mayHaveInlineAsmBr())
     return false;
 
   MachineBasicBlock *PredTBB = nullptr, *PredFBB = nullptr;
@@ -896,7 +896,7 @@
 
     // Update the CFG.
     PredBB->removeSuccessor(PredBB->succ_begin());
-    assert(PredBB->succ_empty() &&
+    assert((PredBB->succ_empty() || PredBB->mayHaveInlineAsmBr()) &&
            "TailDuplicate called on block with multiple successors!");
     for (MachineBasicBlock *Succ : TailBB->successors())
       PredBB->addSuccessor(Succ, MBPI->getEdgeProbability(TailBB, Succ));


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