From 25a3130d89f00f53a23f7fc38250d5dc43e29cfb Mon Sep 17 00:00:00 2001
From: Johannes Doerfert <johannes@jdoerfert.de>
Date: Mon, 19 Jul 2021 15:31:10 -0500
Subject: [Local] Do not introduce a new `llvm.trap` before `unreachable`

This is the second attempt to remove the `llvm.trap` insertion after
https://reviews.llvm.org/rGe14e7bc4b889dfaffb7180d176a03311df2d4ae6
reverted the first one. It is not clear what the exact issue was back
then and it might already be gone by now, it has been >5 years after
all.

Replaces D106299.

Differential Revision: https://reviews.llvm.org/D106308
---
 llvm/lib/Transforms/Utils/Local.cpp | 25 ++++++++-----------------
 1 file changed, 8 insertions(+), 17 deletions(-)

(limited to 'llvm/lib/Transforms/Utils/Local.cpp')

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index d95c053..e36d108 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -2110,8 +2110,8 @@ llvm::removeAllNonTerminatorAndEHPadInstructions(BasicBlock *BB) {
   return {NumDeadInst, NumDeadDbgInst};
 }
 
-unsigned llvm::changeToUnreachable(Instruction *I, bool UseLLVMTrap,
-                                   bool PreserveLCSSA, DomTreeUpdater *DTU,
+unsigned llvm::changeToUnreachable(Instruction *I, bool PreserveLCSSA,
+                                   DomTreeUpdater *DTU,
                                    MemorySSAUpdater *MSSAU) {
   BasicBlock *BB = I->getParent();
 
@@ -2127,14 +2127,6 @@ unsigned llvm::changeToUnreachable(Instruction *I, bool UseLLVMTrap,
     if (DTU)
       UniqueSuccessors.insert(Successor);
   }
-  // Insert a call to llvm.trap right before this.  This turns the undefined
-  // behavior into a hard fail instead of falling through into random code.
-  if (UseLLVMTrap) {
-    Function *TrapFn =
-      Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap);
-    CallInst *CallTrap = CallInst::Create(TrapFn, "", I);
-    CallTrap->setDebugLoc(I->getDebugLoc());
-  }
   auto *UI = new UnreachableInst(I->getContext(), I);
   UI->setDebugLoc(I->getDebugLoc());
 
@@ -2271,7 +2263,7 @@ static bool markAliveBlocks(Function &F,
           if (IntrinsicID == Intrinsic::assume) {
             if (match(CI->getArgOperand(0), m_CombineOr(m_Zero(), m_Undef()))) {
               // Don't insert a call to llvm.trap right before the unreachable.
-              changeToUnreachable(CI, false, false, DTU);
+              changeToUnreachable(CI, false, DTU);
               Changed = true;
               break;
             }
@@ -2287,8 +2279,7 @@ static bool markAliveBlocks(Function &F,
             // still be useful for widening.
             if (match(CI->getArgOperand(0), m_Zero()))
               if (!isa<UnreachableInst>(CI->getNextNode())) {
-                changeToUnreachable(CI->getNextNode(), /*UseLLVMTrap=*/false,
-                                    false, DTU);
+                changeToUnreachable(CI->getNextNode(), false, DTU);
                 Changed = true;
                 break;
               }
@@ -2296,7 +2287,7 @@ static bool markAliveBlocks(Function &F,
         } else if ((isa<ConstantPointerNull>(Callee) &&
                     !NullPointerIsDefined(CI->getFunction())) ||
                    isa<UndefValue>(Callee)) {
-          changeToUnreachable(CI, /*UseLLVMTrap=*/false, false, DTU);
+          changeToUnreachable(CI, false, DTU);
           Changed = true;
           break;
         }
@@ -2306,7 +2297,7 @@ static bool markAliveBlocks(Function &F,
           // though.
           if (!isa<UnreachableInst>(CI->getNextNode())) {
             // Don't insert a call to llvm.trap right before the unreachable.
-            changeToUnreachable(CI->getNextNode(), false, false, DTU);
+            changeToUnreachable(CI->getNextNode(), false, DTU);
             Changed = true;
           }
           break;
@@ -2325,7 +2316,7 @@ static bool markAliveBlocks(Function &F,
             (isa<ConstantPointerNull>(Ptr) &&
              !NullPointerIsDefined(SI->getFunction(),
                                    SI->getPointerAddressSpace()))) {
-          changeToUnreachable(SI, true, false, DTU);
+          changeToUnreachable(SI, false, DTU);
           Changed = true;
           break;
         }
@@ -2339,7 +2330,7 @@ static bool markAliveBlocks(Function &F,
       if ((isa<ConstantPointerNull>(Callee) &&
            !NullPointerIsDefined(BB->getParent())) ||
           isa<UndefValue>(Callee)) {
-        changeToUnreachable(II, true, false, DTU);
+        changeToUnreachable(II, false, DTU);
         Changed = true;
       } else if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(&F)) {
         if (II->use_empty() && II->onlyReadsMemory()) {
-- 
cgit v1.1