[CodeExtractor] Terminate callsite blocks to new `noreturn` functions with `unreachable`

Since some of the users of `CodeExtractor` like `HotColdSplitting` run
late in the pipeline, returns are not cleaned to `unreachable`. So,
just emit `unreachable` directly if the function is `noreturn`.

Closes #84682

11 files changed, 45 insertions, 39 deletions

diff --git a/llvm/lib/Transforms/Utils/CodeExtractor.cpp b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
index 0fac5fc..a43e2ce 100644
--- a/llvm/lib/Transforms/Utils/CodeExtractor.cpp
+++ b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -1010,6 +1010,18 @@ Function *CodeExtractor::constructFunction(const ValueSet &inputs,
 
     newFunction->addFnAttr(Attr);
   }
+
+  if (NumExitBlocks == 0) {
+    // Mark the new function `noreturn` if applicable. Terminators which resume
+    // exception propagation are treated as returning instructions. This is to
+    // avoid inserting traps after calls to outlined functions which unwind.
+    if (none_of(Blocks, [](const BasicBlock *BB) {
+          const Instruction *Term = BB->getTerminator();
+          return isa<ReturnInst>(Term) || isa<ResumeInst>(Term);
+        }))
+      newFunction->setDoesNotReturn();
+  }
+
   newFunction->insert(newFunction->end(), newRootNode);
 
   // Create scalar and aggregate iterators to name all of the arguments we
@@ -1392,19 +1404,23 @@ CallInst *CodeExtractor::emitCallAndSwitchStatement(Function *newFunction,
   case 0:
     // There are no successors (the block containing the switch itself), which
     // means that previously this was the last part of the function, and hence
-    // this should be rewritten as a `ret'
-
-    // Check if the function should return a value
-    if (OldFnRetTy->isVoidTy()) {
-      ReturnInst::Create(Context, nullptr, TheSwitch->getIterator());  // Return void
+    // this should be rewritten as a `ret` or `unreachable`.
+    if (newFunction->doesNotReturn()) {
+      // If fn is no return, end with an unreachable terminator.
+      (void)new UnreachableInst(Context, TheSwitch->getIterator());
+    } else if (OldFnRetTy->isVoidTy()) {
+      // We have no return value.
+      ReturnInst::Create(Context, nullptr,
+                         TheSwitch->getIterator()); // Return void
     } else if (OldFnRetTy == TheSwitch->getCondition()->getType()) {
       // return what we have
-      ReturnInst::Create(Context, TheSwitch->getCondition(), TheSwitch->getIterator());
+      ReturnInst::Create(Context, TheSwitch->getCondition(),
+                         TheSwitch->getIterator());
     } else {
       // Otherwise we must have code extracted an unwind or something, just
       // return whatever we want.
-      ReturnInst::Create(Context,
-                         Constant::getNullValue(OldFnRetTy), TheSwitch->getIterator());
+      ReturnInst::Create(Context, Constant::getNullValue(OldFnRetTy),
+                         TheSwitch->getIterator());
     }
 
     TheSwitch->eraseFromParent();
@@ -1895,16 +1911,6 @@ CodeExtractor::extractCodeRegion(const CodeExtractorAnalysisCache &CEAC,
 
   fixupDebugInfoPostExtraction(*oldFunction, *newFunction, *TheCall);
 
-  // Mark the new function `noreturn` if applicable. Terminators which resume
-  // exception propagation are treated as returning instructions. This is to
-  // avoid inserting traps after calls to outlined functions which unwind.
-  bool doesNotReturn = none_of(*newFunction, [](const BasicBlock &BB) {
-    const Instruction *Term = BB.getTerminator();
-    return isa<ReturnInst>(Term) || isa<ResumeInst>(Term);
-  });
-  if (doesNotReturn)
-    newFunction->setDoesNotReturn();
-
   LLVM_DEBUG(if (verifyFunction(*newFunction, &errs())) {
     newFunction->dump();
     report_fatal_error("verification of newFunction failed!");
diff --git a/llvm/test/Transforms/HotColdSplit/outline-disjoint-diamonds.ll b/llvm/test/Transforms/HotColdSplit/outline-disjoint-diamonds.ll
index 0c05598..55013aa 100644
--- a/llvm/test/Transforms/HotColdSplit/outline-disjoint-diamonds.ll
+++ b/llvm/test/Transforms/HotColdSplit/outline-disjoint-diamonds.ll
@@ -2,9 +2,9 @@
 
 ; CHECK-LABEL: define {{.*}}@fun
 ; CHECK: call {{.*}}@fun.cold.1(
-; CHECK-NEXT: ret void
+; CHECK-NEXT: unreachable
 ; CHECK: call {{.*}}@fun.cold.2(
-; CHECK-NEXT: ret void
+; CHECK-NEXT: unreachable
 define void @fun() {
 entry:
   br i1 undef, label %A.then, label %A.else
diff --git a/llvm/test/Transforms/IROutliner/outlining-no-return-functions.ll b/llvm/test/Transforms/IROutliner/outlining-no-return-functions.ll
index 6b12207..d2c4137 100644
--- a/llvm/test/Transforms/IROutliner/outlining-no-return-functions.ll
+++ b/llvm/test/Transforms/IROutliner/outlining-no-return-functions.ll
@@ -29,19 +29,19 @@ bb1:
 ; CHECK-LABEL: @f1(
 ; CHECK-NEXT:  bb:
 ; CHECK-NEXT:    call void @outlined_ir_func_0()
-; CHECK-NEXT:    ret void
+; CHECK-NEXT:    unreachable
 ;
 ;
 ; CHECK-LABEL: @f2(
 ; CHECK-NEXT:  bb:
 ; CHECK-NEXT:    call void @outlined_ir_func_0()
-; CHECK-NEXT:    ret void
+; CHECK-NEXT:    unreachable
 ;
 ;
 ; CHECK-LABEL: @f3(
 ; CHECK-NEXT:  bb:
 ; CHECK-NEXT:    call void @outlined_ir_func_0()
-; CHECK-NEXT:    ret void
+; CHECK-NEXT:    unreachable
 ;
 ;
 ; CHECK-LABEL: define internal void @outlined_ir_func_0(
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.generated.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.generated.expected
index 02d8870..775649c 100644
--- a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.generated.expected
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.generated.expected
@@ -41,7 +41,7 @@ declare void @_Z10sideeffectv()
 ; CHECK-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; CHECK:       codeRepl:
 ; CHECK-NEXT:    call void @foo.cold.1() #[[ATTR2:[0-9]+]]
-; CHECK-NEXT:    ret void
+; CHECK-NEXT:    unreachable
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
 ;
@@ -52,7 +52,7 @@ declare void @_Z10sideeffectv()
 ; CHECK-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; CHECK:       codeRepl:
 ; CHECK-NEXT:    call void @bar.cold.1() #[[ATTR2]]
-; CHECK-NEXT:    ret void
+; CHECK-NEXT:    unreachable
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
 ;
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.generated.globals.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.generated.globals.expected
index 05e5777..a8086ae 100644
--- a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.generated.globals.expected
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.generated.globals.expected
@@ -44,7 +44,7 @@ declare void @_Z10sideeffectv()
 ; CHECK-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; CHECK:       codeRepl:
 ; CHECK-NEXT:    call void @foo.cold.1() #[[ATTR2:[0-9]+]]
-; CHECK-NEXT:    ret void
+; CHECK-NEXT:    unreachable
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
 ;
@@ -55,7 +55,7 @@ declare void @_Z10sideeffectv()
 ; CHECK-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; CHECK:       codeRepl:
 ; CHECK-NEXT:    call void @bar.cold.1() #[[ATTR2]]
-; CHECK-NEXT:    ret void
+; CHECK-NEXT:    unreachable
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
 ;
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.nogenerated.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.nogenerated.expected
index 36bcbe3..57de350 100644
--- a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.nogenerated.expected
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.nogenerated.expected
@@ -12,7 +12,7 @@ define void @foo(i32) {
 ; CHECK-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; CHECK:       codeRepl:
 ; CHECK-NEXT:    call void @foo.cold.1() #[[ATTR2:[0-9]+]]
-; CHECK-NEXT:    ret void
+; CHECK-NEXT:    unreachable
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
 ;
@@ -36,7 +36,7 @@ define void @bar(i32) {
 ; CHECK-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; CHECK:       codeRepl:
 ; CHECK-NEXT:    call void @bar.cold.1() #[[ATTR2]]
-; CHECK-NEXT:    ret void
+; CHECK-NEXT:    unreachable
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
 ;
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.nogenerated.globals.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.nogenerated.globals.expected
index db7c692..696d5c6e 100644
--- a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.nogenerated.globals.expected
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs.ll.nogenerated.globals.expected
@@ -15,7 +15,7 @@ define void @foo(i32) {
 ; CHECK-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; CHECK:       codeRepl:
 ; CHECK-NEXT:    call void @foo.cold.1() #[[ATTR2:[0-9]+]]
-; CHECK-NEXT:    ret void
+; CHECK-NEXT:    unreachable
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
 ;
@@ -39,7 +39,7 @@ define void @bar(i32) {
 ; CHECK-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; CHECK:       codeRepl:
 ; CHECK-NEXT:    call void @bar.cold.1() #[[ATTR2]]
-; CHECK-NEXT:    ret void
+; CHECK-NEXT:    unreachable
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
 ;
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.expected
index 1039995..5275870 100644
--- a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.expected
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.expected
@@ -42,7 +42,7 @@ declare void @_Z10sideeffectv()
 ; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; REUSE:       codeRepl:
 ; REUSE-NEXT:    call void @foo.cold.1() #[[ATTR2:[0-9]+]]
-; REUSE-NEXT:    ret void
+; REUSE-NEXT:    unreachable
 ; REUSE:       exit:
 ; REUSE-NEXT:    ret void
 ;
@@ -53,7 +53,7 @@ declare void @_Z10sideeffectv()
 ; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; REUSE:       codeRepl:
 ; REUSE-NEXT:    call void @bar.cold.1() #[[ATTR2]]
-; REUSE-NEXT:    ret void
+; REUSE-NEXT:    unreachable
 ; REUSE:       exit:
 ; REUSE-NEXT:    ret void
 ;
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.globals.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.globals.expected
index 0001790..712ccb2 100644
--- a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.globals.expected
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.globals.expected
@@ -45,7 +45,7 @@ declare void @_Z10sideeffectv()
 ; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; REUSE:       codeRepl:
 ; REUSE-NEXT:    call void @foo.cold.1() #[[ATTR2:[0-9]+]]
-; REUSE-NEXT:    ret void
+; REUSE-NEXT:    unreachable
 ; REUSE:       exit:
 ; REUSE-NEXT:    ret void
 ;
@@ -56,7 +56,7 @@ declare void @_Z10sideeffectv()
 ; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; REUSE:       codeRepl:
 ; REUSE-NEXT:    call void @bar.cold.1() #[[ATTR2]]
-; REUSE-NEXT:    ret void
+; REUSE-NEXT:    unreachable
 ; REUSE:       exit:
 ; REUSE-NEXT:    ret void
 ;
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.expected
index e05a57d..b5b12b7 100644
--- a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.expected
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.expected
@@ -13,7 +13,7 @@ define void @foo(i32) {
 ; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; REUSE:       codeRepl:
 ; REUSE-NEXT:    call void @foo.cold.1() #[[ATTR2:[0-9]+]]
-; REUSE-NEXT:    ret void
+; REUSE-NEXT:    unreachable
 ; REUSE:       exit:
 ; REUSE-NEXT:    ret void
 ;
@@ -37,7 +37,7 @@ define void @bar(i32) {
 ; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; REUSE:       codeRepl:
 ; REUSE-NEXT:    call void @bar.cold.1() #[[ATTR2]]
-; REUSE-NEXT:    ret void
+; REUSE-NEXT:    unreachable
 ; REUSE:       exit:
 ; REUSE-NEXT:    ret void
 ;
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.globals.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.globals.expected
index 17be222..7e2b991 100644
--- a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.globals.expected
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.globals.expected
@@ -16,7 +16,7 @@ define void @foo(i32) {
 ; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; REUSE:       codeRepl:
 ; REUSE-NEXT:    call void @foo.cold.1() #[[ATTR2:[0-9]+]]
-; REUSE-NEXT:    ret void
+; REUSE-NEXT:    unreachable
 ; REUSE:       exit:
 ; REUSE-NEXT:    ret void
 ;
@@ -40,7 +40,7 @@ define void @bar(i32) {
 ; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
 ; REUSE:       codeRepl:
 ; REUSE-NEXT:    call void @bar.cold.1() #[[ATTR2]]
-; REUSE-NEXT:    ret void
+; REUSE-NEXT:    unreachable
 ; REUSE:       exit:
 ; REUSE-NEXT:    ret void
 ;