[SCCP] Remove code redundancy in resolvedUndefsIn

[ksyx]

Summary

Merge similar logic at the end of processing each type of switch/branch instructions into one to make code more clear.

[lattner]

I'd prefer it if someone else could review this code. It has been a very long time since I've touched it.

[ksyx]

refactor: apply clang format

[fhahn]

I think the relevant code has been removed/refactored.

[ksyx]

Thanks for the information. This part of code was removed in https://github.com/llvm/llvm-project/commit/1f88d804083a8a1b68df1e6677920e38ab2a6b40#diff-d5b2ea0042a8c02ed8ab1a2ec072423c9fdb5d72f2be64777bc99faa9b8ca032 and it looks clean now.

llvm/lib/Transforms/Utils/SCCPSolver.cpp

for (Instruction &I : BB) {
       markOverdefined(&I);
       MadeChange = true;
     }
 
     // Check to see if we have a branch or switch on an undefined value.  If so
     // we force the branch to go one way or the other to make the successor
     // values live.  It doesn't really matter which way we force it.
     Instruction *TI = BB.getTerminator();
-    if (auto *BI = dyn_cast<BranchInst>(TI)) {
-      if (!BI->isConditional())
-        continue;
-      if (!getValueState(BI->getCondition()).isUnknownOrUndef())
+    auto *BI = dyn_cast<BranchInst>(TI);
+    auto *IBR = dyn_cast<IndirectBrInst>(TI);
+    auto *SI = dyn_cast<SwitchInst>(TI);
+    if (BI || IBR || SI) {
+      BasicBlock *DefaultSuccessor = nullptr;
+      if (BI) {
+        if (!BI->isConditional() ||
+            !getValueState(BI->getCondition()).isUnknownOrUndef())
           continue;
 
         // If the input to SCCP is actually branch on undef, fix the undef to
         // false.
         if (isa<UndefValue>(BI->getCondition())) {
           BI->setCondition(ConstantInt::getFalse(BI->getContext()));
-        markEdgeExecutable(&BB, TI->getSuccessor(1));
           MadeChange = true;
-        continue;
         }
-
-      // Otherwise, it is a branch on a symbolic value which is currently
-      // considered to be undef.  Make sure some edge is executable, so a
-      // branch on "undef" always flows somewhere.
-      // FIXME: Distinguish between dead code and an LLVM "undef" value.
-      BasicBlock *DefaultSuccessor = TI->getSuccessor(1);
-      if (markEdgeExecutable(&BB, DefaultSuccessor))
-        MadeChange = true;
-
-      continue;
-    }
-
-    if (auto *IBR = dyn_cast<IndirectBrInst>(TI)) {
-      // Indirect branch with no successor ?. Its ok to assume it branches
+        DefaultSuccessor = TI->getSuccessor(1);
+      } else if (IBR) {
+        // Indirect branch with no successor? It's ok to assume it branches
         // to no target.
-      if (IBR->getNumSuccessors() < 1)
-        continue;
-
-      if (!getValueState(IBR->getAddress()).isUnknownOrUndef())
+        if (IBR->getNumSuccessors() < 1 ||
+            !getValueState(IBR->getAddress()).isUnknownOrUndef())
           continue;
 
         // If the input to SCCP is actually branch on undef, fix the undef to
         // the first successor of the indirect branch.
         if (isa<UndefValue>(IBR->getAddress())) {
           IBR->setAddress(BlockAddress::get(IBR->getSuccessor(0)));
-        markEdgeExecutable(&BB, IBR->getSuccessor(0));
           MadeChange = true;
-        continue;
-      }
-
-      // Otherwise, it is a branch on a symbolic value which is currently
-      // considered to be undef.  Make sure some edge is executable, so a
-      // branch on "undef" always flows somewhere.
-      // FIXME: IndirectBr on "undef" doesn't actually need to go anywhere:
-      // we can assume the branch has undefined behavior instead.
-      BasicBlock *DefaultSuccessor = IBR->getSuccessor(0);
-      if (markEdgeExecutable(&BB, DefaultSuccessor))
-        MadeChange = true;
-
-      continue;
         }
-
-    if (auto *SI = dyn_cast<SwitchInst>(TI)) {
+        DefaultSuccessor = IBR->getSuccessor(0);
+      } else if (SI) {
         if (!SI->getNumCases() ||
             !getValueState(SI->getCondition()).isUnknownOrUndef())
           continue;
 
         // If the input to SCCP is actually switch on undef, fix the undef to
         // the first constant.
         if (isa<UndefValue>(SI->getCondition())) {
           SI->setCondition(SI->case_begin()->getCaseValue());
-        markEdgeExecutable(&BB, SI->case_begin()->getCaseSuccessor());
           MadeChange = true;
-        continue;
         }
+        DefaultSuccessor = SI->case_begin()->getCaseSuccessor();
+      } else
+        llvm_unreachable("Unexpected branch type.");
+
+      assert(DefaultSuccessor && "Default successor unset.");
 
       // Otherwise, it is a branch on a symbolic value which is currently
       // considered to be undef.  Make sure some edge is executable, so a
       // branch on "undef" always flows somewhere.
       // FIXME: Distinguish between dead code and an LLVM "undef" value.
-      BasicBlock *DefaultSuccessor = SI->case_begin()->getCaseSuccessor();
       if (markEdgeExecutable(&BB, DefaultSuccessor))
         MadeChange = true;
 
       continue;
     }
   }
 
   return MadeChange;