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Make RecursivelyDeleteDeadPHINode delete a phi node that has no users and add a

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test for that. With this change, test/CodeGen/X86/codegen-dce.ll no longer finds
any instructions to DCE, so delete the test.

Also renamed J and JP to I and IP in RecursivelyDeleteDeadPHINode.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126088 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2011-02-20 18:05:56 +00:00
parent cd6c93ec48
commit eff5e69c82
3 changed files with 17 additions and 50 deletions
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19
lib/Transforms/Utils/Local.cpp
View File

@ -283,6 +283,11 @@ static bool areAllUsesEqual(Instruction *I) {
/// delete it. If that makes any of its operands trivially dead, delete them
/// too, recursively. Return true if the PHI node is actually deleted.
bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN) {
if (PN->use_empty()) {
PN->eraseFromParent();
return true;
}
// We can remove a PHI if it is on a cycle in the def-use graph
// where each node in the cycle has degree one, i.e. only one use,
// and is an instruction with no side effects.
@ -292,16 +297,16 @@ bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN) {
bool Changed = false;
SmallPtrSet<PHINode *, 4> PHIs;
PHIs.insert(PN);
for (Instruction *J = cast<Instruction>(*PN->use_begin());
areAllUsesEqual(J) && !J->mayHaveSideEffects();
J = cast<Instruction>(*J->use_begin()))
for (Instruction *I = cast<Instruction>(*PN->use_begin());
areAllUsesEqual(I) && !I->mayHaveSideEffects();
I = cast<Instruction>(*I->use_begin()))
// If we find a PHI more than once, we're on a cycle that
// won't prove fruitful.
if (PHINode *JP = dyn_cast<PHINode>(J))
if (!PHIs.insert(JP)) {
if (PHINode *IP = dyn_cast<PHINode>(I))
if (!PHIs.insert(IP)) {
// Break the cycle and delete the PHI and its operands.
JP->replaceAllUsesWith(UndefValue::get(JP->getType()));
(void)RecursivelyDeleteTriviallyDeadInstructions(JP);
IP->replaceAllUsesWith(UndefValue::get(IP->getType()));
(void)RecursivelyDeleteTriviallyDeadInstructions(IP);
Changed = true;
break;
}

43
test/CodeGen/X86/codegen-dce.ll
View File

@ -1,43 +0,0 @@
; RUN: llc < %s -march=x86 -stats |& grep {codegen-dce} | grep {Number of dead instructions deleted}
%struct.anon = type { [3 x double], double, %struct.node*, [64 x %struct.bnode*], [64 x %struct.bnode*] }
%struct.bnode = type { i16, double, [3 x double], i32, i32, [3 x double], [3 x double], [3 x double], double, %struct.bnode*, %struct.bnode* }
%struct.node = type { i16, double, [3 x double], i32, i32 }
define i32 @main(i32 %argc, i8** nocapture %argv) nounwind {
entry:
%0 = malloc %struct.anon ; <%struct.anon*> [#uses=2]
%1 = getelementptr %struct.anon* %0, i32 0, i32 2 ; <%struct.node**> [#uses=1]
br label %bb14.i
bb14.i: ; preds = %bb14.i, %entry
%i8.0.reg2mem.0.i = phi i32 [ 0, %entry ], [ %2, %bb14.i ] ; <i32> [#uses=1]
%2 = add i32 %i8.0.reg2mem.0.i, 1 ; <i32> [#uses=2]
%exitcond74.i = icmp eq i32 %2, 32 ; <i1> [#uses=1]
br i1 %exitcond74.i, label %bb32.i, label %bb14.i
bb32.i: ; preds = %bb32.i, %bb14.i
%tmp.0.reg2mem.0.i = phi i32 [ %indvar.next63.i, %bb32.i ], [ 0, %bb14.i ] ; <i32> [#uses=1]
%indvar.next63.i = add i32 %tmp.0.reg2mem.0.i, 1 ; <i32> [#uses=2]
%exitcond64.i = icmp eq i32 %indvar.next63.i, 64 ; <i1> [#uses=1]
br i1 %exitcond64.i, label %bb47.loopexit.i, label %bb32.i
bb.i.i: ; preds = %bb47.loopexit.i
unreachable
stepsystem.exit.i: ; preds = %bb47.loopexit.i
store %struct.node* null, %struct.node** %1, align 4
br label %bb.i6.i
bb.i6.i: ; preds = %bb.i6.i, %stepsystem.exit.i
br i1 false, label %bb107.i.i, label %bb.i6.i
bb107.i.i: ; preds = %bb107.i.i, %bb.i6.i
%q_addr.0.i.i.in = phi %struct.bnode** [ null, %bb107.i.i ], [ %3, %bb.i6.i ] ; <%struct.bnode**> [#uses=0]
br label %bb107.i.i
bb47.loopexit.i: ; preds = %bb32.i
%3 = getelementptr %struct.anon* %0, i32 0, i32 4, i32 0 ; <%struct.bnode**> [#uses=1]
%4 = icmp eq %struct.node* null, null ; <i1> [#uses=1]
br i1 %4, label %stepsystem.exit.i, label %bb.i.i
}

5
unittests/Transforms/Utils/Local.cpp
View File

@ -42,6 +42,11 @@ TEST(Local, RecursivelyDeleteDeadPHINodes) {
EXPECT_EQ(&bb0->front(), br0);
EXPECT_EQ(&bb1->front(), br1);
builder.SetInsertPoint(bb0);
phi = builder.CreatePHI(Type::getInt32Ty(C));
EXPECT_TRUE(RecursivelyDeleteDeadPHINode(phi));
bb0->dropAllReferences();
bb1->dropAllReferences();
delete bb0;