[PATCH] D117810: [InstCombine] Instruction sinking: fix check for function terminating block

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: reames, spatel, jcranmer.
lebedev.ri added a project: LLVM.
Herald added a subscriber: hiraditya.
lebedev.ri requested review of this revision.

Checking for specific function terminating opcodes
means we don't handle other non-hardcoded ones :)

This should probably be generalized to something
similar to the `IsBlockFollowedByDeoptOrUnreachable()`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D117810

Files:
  llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
  llvm/test/Transforms/InstCombine/sink-into-resume-block.ll


Index: llvm/test/Transforms/InstCombine/sink-into-resume-block.ll
===================================================================
--- llvm/test/Transforms/InstCombine/sink-into-resume-block.ll
+++ llvm/test/Transforms/InstCombine/sink-into-resume-block.ll
@@ -7,7 +7,6 @@
 ; CHECK-LABEL: @t0_noop(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[C:%.*]] = call i1 @cond()
-; CHECK-NEXT:    [[V0:%.*]] = add i32 [[ARG:%.*]], 42
 ; CHECK-NEXT:    br i1 [[C]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
 ; CHECK:       if.then:
 ; CHECK-NEXT:    invoke void @simple_throw()
@@ -17,6 +16,7 @@
 ; CHECK:       lpad:
 ; CHECK-NEXT:    [[EH:%.*]] = landingpad { i8*, i32 }
 ; CHECK-NEXT:    cleanup
+; CHECK-NEXT:    [[V0:%.*]] = add i32 [[ARG:%.*]], 42
 ; CHECK-NEXT:    call void @consume(i32 [[V0]])
 ; CHECK-NEXT:    call void @destructor()
 ; CHECK-NEXT:    resume { i8*, i32 } [[EH]]
Index: llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3966,12 +3966,11 @@
       // predecessor, so that we don't have to split the critical edge.
       // Another option where we can sink is a block that ends with a
       // terminator that does not pass control to other block (such as
-      // return or unreachable). In this case:
+      // return or unreachable or resume). In this case:
       //   - I dominates the User (by SSA form);
       //   - the User will be executed at most once.
       // So sinking I down to User is always profitable or neutral.
-      if (UserParent->getUniquePredecessor() == BB ||
-          (isa<ReturnInst>(Term) || isa<UnreachableInst>(Term))) {
+      if (UserParent->getUniquePredecessor() == BB || succ_empty(Term)) {
         assert(DT.dominates(BB, UserParent) && "Dominance relation broken?");
         return UserParent;
       }


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