make simplifyCFG erase invokes to readonly/readnone functions

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159385 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 47 insertions, 7 deletions

diff --git a/lib/Transforms/Scalar/SimplifyCFGPass.cpp b/lib/Transforms/Scalar/SimplifyCFGPass.cpp
index 5943697..bdcf988 100644
--- a/lib/Transforms/Scalar/SimplifyCFGPass.cpp
+++ b/lib/Transforms/Scalar/SimplifyCFGPass.cpp
@@ -89,7 +89,6 @@ static void ChangeToUnreachable(Instruction *I, bool UseLLVMTrap) {
 
 /// ChangeToCall - Convert the specified invoke into a normal call.
 static void ChangeToCall(InvokeInst *II) {
-  BasicBlock *BB = II->getParent();
   SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
   CallInst *NewCall = CallInst::Create(II->getCalledValue(), Args, "", II);
   NewCall->takeName(II);
@@ -100,10 +99,7 @@ static void ChangeToCall(InvokeInst *II) {
 
   // Follow the call by a branch to the normal destination.
   BranchInst::Create(II->getNormalDest(), II);
-
-  // Update PHI nodes in the unwind destination
-  II->getUnwindDest()->removePredecessor(BB);
-  BB->getInstList().erase(II);
+  II->eraseFromParent();
 }
 
 static bool MarkAliveBlocks(BasicBlock *BB,
@@ -163,7 +159,12 @@ static bool MarkAliveBlocks(BasicBlock *BB,
         ChangeToUnreachable(II, true);
         Changed = true;
       } else if (II->doesNotThrow()) {
-        ChangeToCall(II);
+        if (II->use_empty() && II->onlyReadsMemory()) {
+          // jump to the normal destination branch.
+          BranchInst::Create(II->getNormalDest(), II);
+          II->eraseFromParent();
+        } else
+          ChangeToCall(II);
         Changed = true;
       }
     }
diff --git a/test/Transforms/SimplifyCFG/invoke.ll b/test/Transforms/SimplifyCFG/invoke.ll
index c9169d4..18c6b8e 100644
--- a/test/Transforms/SimplifyCFG/invoke.ll
+++ b/test/Transforms/SimplifyCFG/invoke.ll
@@ -3,7 +3,7 @@ target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f3
 
 declare i32 @__gxx_personality_v0(...)
 declare void @__cxa_call_unexpected(i8*)
-declare i64 @llvm.objectsize.i64(i8*, i1) nounwind readonly
+declare i32 @read_only() nounwind readonly
 
 
 ; CHECK: @f1
@@ -43,3 +43,42 @@ lpad:
   tail call void @__cxa_call_unexpected(i8* %1) noreturn nounwind
   unreachable
 }
+
+; CHECK: @f3
+define i32 @f3() nounwind uwtable ssp {
+; CHECK-NEXT: entry
+entry:
+; CHECK-NEXT: ret i32 3
+  %call = invoke i32 @read_only()
+          to label %invoke.cont unwind label %lpad
+
+invoke.cont:
+  ret i32 3
+
+lpad:
+  %0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          filter [0 x i8*] zeroinitializer
+  %1 = extractvalue { i8*, i32 } %0, 0
+  tail call void @__cxa_call_unexpected(i8* %1) noreturn nounwind
+  unreachable
+}
+
+; CHECK: @f4
+define i32 @f4() nounwind uwtable ssp {
+; CHECK-NEXT: entry
+entry:
+; CHECK-NEXT: call i32 @read_only()
+  %call = invoke i32 @read_only()
+          to label %invoke.cont unwind label %lpad
+
+invoke.cont:
+; CHECK-NEXT: ret i32 %call
+  ret i32 %call
+
+lpad:
+  %0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          filter [0 x i8*] zeroinitializer
+  %1 = extractvalue { i8*, i32 } %0, 0
+  tail call void @__cxa_call_unexpected(i8* %1) noreturn nounwind
+  unreachable
+}