[Transforms][CodeExtraction] bug fix regions with stackrestore

   Ensure code extraction for outlining to a function does not
  create a function with tail-call i.e. using stacksave of caller
  to restore stack. Code Extractor can include all other
  basic blocks without such stack restore blocks.

symmetric scenario with stacksave with out-of-fn use

Author: AbhayKanhere

llvm/lib/Transforms/Utils/CodeExtractor.cpp

@@ -627,6 +627,31 @@ bool CodeExtractor::isEligible() const {
         return false;
     }
   }
+  // stacksave as input implies stackrestore in the outlined function
+  // This can confuse prologue epilogue insertion phase
+  // stacksave's uses must not cross outlined function
+  for (BasicBlock *BB : Blocks) {
+    for (Instruction &II : *BB) {
+      if (IntrinsicInst *Intrin = dyn_cast<IntrinsicInst>(&II)) {
+        if (Intrin->getIntrinsicID() == Intrinsic::stacksave) {
+          for (User *U : Intrin->users())
+            if (!definedInRegion(Blocks, U)) {
+              return false; // stack-restore outside outlined region
+            }
+        }
+      }
+      for (auto &OI : II.operands()) {
+        Value *V = OI;
+        if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(V)) {
+          if (II->getIntrinsicID() == Intrinsic::stacksave) {
+            if (definedInCaller(Blocks, V)) {
+              return false;
+            }
+          }
+        }
+      }
+    }
+  }
   return true;
 }
 

llvm/test/Transforms/HotColdSplit/outline-inner-region-stacktoocomplex.ll

@@ -0,0 +1,51 @@
+; RUN: opt -S -passes=hotcoldsplit -hotcoldsplit-max-params=1 < %s | FileCheck %s
+
+target datalayout = "E-m:a-p:32:32-i64:64-n32"
+target triple = "powerpc64-ibm-aix7.2.0.0"
+
+define void @foo(i32 %cond) {
+; CHECK-LABEL: define {{.*}}@foo(
+; CHECK:       if.then:
+; CHECK:       if.then1:
+; CHECK:       if.else:
+; CHECK:       call {{.*}}@sink
+; CHECK:       if.end:
+; CHECK:       if.end2:
+;
+entry:
+  %cond.addr = alloca i32
+  store i32 %cond, ptr %cond.addr
+  %0 = load i32, ptr %cond.addr
+  %stks =  tail call ptr @llvm.stacksave.p0()
+  %tobool = icmp ne i32 %0, 0
+  br i1 %tobool, label %if.then, label %if.end2
+
+if.then:                                          ; preds = %entry
+  %1 = load i32, ptr %cond.addr
+  call void @sink(i32 %0)
+  %cmp = icmp sgt i32 %1, 10
+  br i1 %cmp, label %if.then1, label %if.else
+
+if.then1:                                         ; preds = %if.then
+  call void @sideeffect(i32 2)
+  br label %if.end
+
+if.else:                                          ; preds = %if.then
+  call void @sink(i32 0)
+  call void @sideeffect(i32 0)
+  call void @llvm.stackrestore.p0(ptr %stks)
+  br label %if.end
+
+
+if.end:                                           ; preds = %if.else, %if.then1
+  br label %if.end2
+
+if.end2:                                          ; preds = %entry
+  call void @sideeffect(i32 1)
+  ret void
+}
+
+
+declare void @sideeffect(i32)
+
+declare void @sink(i32) cold