[llvm-commits] [llvm] r131855 - in /llvm/trunk: include/llvm/Transforms/Utils/Local.h lib/Transforms/Scalar/CodeGenPrepare.cpp lib/Transforms/Scalar/JumpThreading.cpp lib/Transforms/Scalar/SimplifyCFGPass.cpp lib/Transforms/Utils/Local.cpp lib/Transforms/Utils/SimplifyCFG.cpp test/Transforms/SimplifyCFG/dce-cond-after-folding-terminator.ll
Frits van Bommel
fvbommel at gmail.com
Sun May 22 09:24:18 PDT 2011
Author: fvbommel
Date: Sun May 22 11:24:18 2011
New Revision: 131855
URL: http://llvm.org/viewvc/llvm-project?rev=131855&view=rev
Log:
Add a parameter to ConstantFoldTerminator() that callers can use to ask it to also clean up the condition of any conditional terminator it folds to be unconditional, if that turns the condition into dead code. This just means it calls RecursivelyDeleteTriviallyDeadInstructions() in strategic spots. It defaults to the old behavior.
I also changed -simplifycfg, -jump-threading and -codegenprepare to use this to produce slightly better code without any extra cleanup passes (AFAICT this was the only place in -simplifycfg where now-dead conditions of replaced terminators weren't being cleaned up). The only other user of this function is -sccp, but I didn't read that thoroughly enough to figure out whether it might be holding pointers to instructions that could be deleted by this.
Added:
llvm/trunk/test/Transforms/SimplifyCFG/dce-cond-after-folding-terminator.ll
Modified:
llvm/trunk/include/llvm/Transforms/Utils/Local.h
llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp
llvm/trunk/lib/Transforms/Utils/Local.cpp
llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
Modified: llvm/trunk/include/llvm/Transforms/Utils/Local.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/Local.h?rev=131855&r1=131854&r2=131855&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/Local.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/Local.h Sun May 22 11:24:18 2011
@@ -43,8 +43,10 @@
/// constant value, convert it into an unconditional branch to the constant
/// destination. This is a nontrivial operation because the successors of this
/// basic block must have their PHI nodes updated.
-///
-bool ConstantFoldTerminator(BasicBlock *BB);
+/// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
+/// conditions and indirectbr addresses this might make dead if
+/// DeleteDeadConditions is true.
+bool ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions = false);
//===----------------------------------------------------------------------===//
// Local dead code elimination.
Modified: llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp?rev=131855&r1=131854&r2=131855&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp Sun May 22 11:24:18 2011
@@ -147,7 +147,7 @@
if (!DisableBranchOpts) {
MadeChange = false;
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
- MadeChange |= ConstantFoldTerminator(BB);
+ MadeChange |= ConstantFoldTerminator(BB, true);
if (MadeChange)
ModifiedDT = true;
Modified: llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=131855&r1=131854&r2=131855&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp Sun May 22 11:24:18 2011
@@ -706,7 +706,7 @@
DEBUG(dbgs() << " In block '" << BB->getName()
<< "' folding terminator: " << *BB->getTerminator() << '\n');
++NumFolds;
- ConstantFoldTerminator(BB);
+ ConstantFoldTerminator(BB, true);
return true;
}
Modified: llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp?rev=131855&r1=131854&r2=131855&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp Sun May 22 11:24:18 2011
@@ -163,7 +163,7 @@
Changed = true;
}
- Changed |= ConstantFoldTerminator(BB);
+ Changed |= ConstantFoldTerminator(BB, true);
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
Worklist.push_back(*SI);
} while (!Worklist.empty());
Modified: llvm/trunk/lib/Transforms/Utils/Local.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/Local.cpp?rev=131855&r1=131854&r2=131855&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/Local.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/Local.cpp Sun May 22 11:24:18 2011
@@ -44,11 +44,14 @@
// Local constant propagation.
//
-// ConstantFoldTerminator - If a terminator instruction is predicated on a
-// constant value, convert it into an unconditional branch to the constant
-// destination.
-//
-bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
+/// ConstantFoldTerminator - If a terminator instruction is predicated on a
+/// constant value, convert it into an unconditional branch to the constant
+/// destination. This is a nontrivial operation because the successors of this
+/// basic block must have their PHI nodes updated.
+/// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
+/// conditions and indirectbr addresses this might make dead if
+/// DeleteDeadConditions is true.
+bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions) {
TerminatorInst *T = BB->getTerminator();
IRBuilder<> Builder(T);
@@ -89,7 +92,10 @@
// Replace the conditional branch with an unconditional one.
Builder.CreateBr(Dest1);
+ Value *Cond = BI->getCondition();
BI->eraseFromParent();
+ if (DeleteDeadConditions)
+ RecursivelyDeleteTriviallyDeadInstructions(Cond);
return true;
}
return false;
@@ -152,7 +158,10 @@
}
// Delete the old switch.
- BB->getInstList().erase(SI);
+ Value *Cond = SI->getCondition();
+ SI->eraseFromParent();
+ if (DeleteDeadConditions)
+ RecursivelyDeleteTriviallyDeadInstructions(Cond);
return true;
}
@@ -186,7 +195,10 @@
else
IBI->getDestination(i)->removePredecessor(IBI->getParent());
}
+ Value *Address = IBI->getAddress();
IBI->eraseFromParent();
+ if (DeleteDeadConditions)
+ RecursivelyDeleteTriviallyDeadInstructions(Address);
// If we didn't find our destination in the IBI successor list, then we
// have undefined behavior. Replace the unconditional branch with an
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=131855&r1=131854&r2=131855&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Sun May 22 11:24:18 2011
@@ -2651,7 +2651,7 @@
// Check to see if we can constant propagate this terminator instruction
// away...
- Changed |= ConstantFoldTerminator(BB);
+ Changed |= ConstantFoldTerminator(BB, true);
// Check for and eliminate duplicate PHI nodes in this block.
Changed |= EliminateDuplicatePHINodes(BB);
Added: llvm/trunk/test/Transforms/SimplifyCFG/dce-cond-after-folding-terminator.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/dce-cond-after-folding-terminator.ll?rev=131855&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/dce-cond-after-folding-terminator.ll (added)
+++ llvm/trunk/test/Transforms/SimplifyCFG/dce-cond-after-folding-terminator.ll Sun May 22 11:24:18 2011
@@ -0,0 +1,52 @@
+; RUN: opt -S <%s -simplifycfg | FileCheck %s
+
+define void @test_br(i32 %x) {
+entry:
+; CHECK: @test_br
+; CHECK-NEXT: entry:
+; CHECK-NEXT: ret void
+ %cmp = icmp eq i32 %x, 10
+ br i1 %cmp, label %if.then, label %if.then
+
+if.then: ; preds = %entry
+ br label %if.end
+
+if.end: ; preds = %if.else, %if.then
+ ret void
+}
+
+define void @test_switch(i32 %x) nounwind {
+entry:
+; CHECK: @test_switch
+; CHECK-NEXT: entry:
+; CHECK-NEXT: ret void
+ %rem = srem i32 %x, 3
+ switch i32 %rem, label %sw.bb [
+ i32 1, label %sw.bb
+ i32 10, label %sw.bb
+ ]
+
+sw.bb: ; preds = %sw.default, %entry, %entry
+ br label %sw.epilog
+
+sw.epilog: ; preds = %sw.bb
+ ret void
+}
+
+define void @test_indirectbr(i32 %x) {
+entry:
+; CHECK: @test_indirectbr
+; CHECK-NEXT: entry:
+; Ideally this should now check:
+; CHK-NEXT: ret void
+; But that doesn't happen yet. Instead:
+; CHECK-NEXT: br label %L1
+
+ %label = bitcast i8* blockaddress(@test_indirectbr, %L1) to i8*
+ indirectbr i8* %label, [label %L1, label %L2]
+
+L1: ; preds = %entry
+ ret void
+L2: ; preds = %entry
+ ret void
+}
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