[llvm] r288725 - [SCCP] Remove manual folding of terminator instructions.
Davide Italiano via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 5 15:04:22 PST 2016
Author: davide
Date: Mon Dec 5 17:04:21 2016
New Revision: 288725
URL: http://llvm.org/viewvc/llvm-project?rev=288725&view=rev
Log:
[SCCP] Remove manual folding of terminator instructions.
There are two cases handled here:
1) a branch on undef
2) a switch with an undef condition.
Both cases are currently handled by ResolvedUndefsIn. If we have
a branch on undef, we force its value to false (which is trivially
foldable). If we have a switch on undef, we force to the first
constant (which is also foldable).
Modified:
llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SCCP.cpp?rev=288725&r1=288724&r2=288725&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SCCP.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SCCP.cpp Mon Dec 5 17:04:21 2016
@@ -1828,33 +1828,8 @@ static bool runIPSCCP(Module &M, const D
// Ignore blockaddress users; BasicBlock's dtor will handle them.
if (!I) continue;
- bool Folded = ConstantFoldTerminator(I->getParent());
- if (!Folded) {
- // The constant folder may not have been able to fold the terminator
- // if this is a branch or switch on undef. Fold it manually as a
- // branch to the first successor.
-#ifndef NDEBUG
- if (auto *BI = dyn_cast<BranchInst>(I)) {
- assert(BI->isConditional() && isa<UndefValue>(BI->getCondition()) &&
- "Branch should be foldable!");
- } else if (auto *SI = dyn_cast<SwitchInst>(I)) {
- assert(isa<UndefValue>(SI->getCondition()) && "Switch should fold");
- } else {
- llvm_unreachable("Didn't fold away reference to block!");
- }
-#endif
-
- // Make this an uncond branch to the first successor.
- TerminatorInst *TI = I->getParent()->getTerminator();
- BranchInst::Create(TI->getSuccessor(0), TI);
-
- // Remove entries in successor phi nodes to remove edges.
- for (unsigned i = 1, e = TI->getNumSuccessors(); i != e; ++i)
- TI->getSuccessor(i)->removePredecessor(TI->getParent());
-
- // Remove the old terminator.
- TI->eraseFromParent();
- }
+ assert(ConstantFoldTerminator(I->getParent()) &&
+ "Terminator should've been folded");
}
// Finally, delete the basic block.
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