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If two-address def is dead and the instruction does not define other registers, and it doesn't produce side effects, just delete the instruction.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@65218 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -53,6 +53,7 @@ STATISTIC(NumAggrCommuted , "Number of instructions aggressively commuted");
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STATISTIC(NumConvertedTo3Addr, "Number of instructions promoted to 3-address");
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STATISTIC(Num3AddrSunk, "Number of 3-address instructions sunk");
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STATISTIC(NumReMats, "Number of instructions re-materialized");
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STATISTIC(NumDeletes, "Number of dead instructions deleted");
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namespace {
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class VISIBILITY_HIDDEN TwoAddressInstructionPass
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@ -371,6 +372,26 @@ TwoAddressInstructionPass::CommuteInstruction(MachineBasicBlock::iterator &mi,
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return true;
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}
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/// isSafeToDelete - If the specified instruction does not produce any side
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/// effects and all of its defs are dead, then it's safe to delete.
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static bool isSafeToDelete(MachineInstr *MI, const TargetInstrInfo *TII) {
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const TargetInstrDesc &TID = MI->getDesc();
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if (TID.mayStore() || TID.isCall())
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return false;
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if (TID.isTerminator() || TID.hasUnmodeledSideEffects())
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return false;
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for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
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MachineOperand &MO = MI->getOperand(i);
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if (!MO.isReg() || !MO.isDef())
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continue;
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if (!MO.isDead())
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return false;
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}
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return true;
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}
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/// runOnMachineFunction - Reduce two-address instructions to two operands.
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///
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bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) {
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@ -450,6 +471,15 @@ bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) {
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// allow us to coalesce A and B together, eliminating the copy we are
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// about to insert.
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if (!mi->killsRegister(regB)) {
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// If regA is dead and the instruction can be deleted, just delete
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// it so it doesn't clobber regB.
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if (mi->getOperand(ti).isDead() && isSafeToDelete(mi, TII)) {
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mbbi->erase(mi); // Nuke the old inst.
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mi = nmi;
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++NumDeletes;
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break; // Done with this instruction.
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}
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// If this instruction is commutative, check to see if C dies. If
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// so, swap the B and C operands. This makes the live ranges of A
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// and C joinable.
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43
test/CodeGen/X86/twoaddr-delete.ll
Normal file
43
test/CodeGen/X86/twoaddr-delete.ll
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@ -0,0 +1,43 @@
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; RUN: llvm-as < %s | llc -march=x86 -stats |& grep {twoaddrinstr} | grep {Number of dead instructions deleted}
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%struct.anon = type { [3 x double], double, %struct.node*, [64 x %struct.bnode*], [64 x %struct.bnode*] }
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%struct.bnode = type { i16, double, [3 x double], i32, i32, [3 x double], [3 x double], [3 x double], double, %struct.bnode*, %struct.bnode* }
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%struct.node = type { i16, double, [3 x double], i32, i32 }
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define i32 @main(i32 %argc, i8** nocapture %argv) nounwind {
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entry:
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%0 = malloc %struct.anon ; <%struct.anon*> [#uses=2]
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%1 = getelementptr %struct.anon* %0, i32 0, i32 2 ; <%struct.node**> [#uses=1]
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br label %bb14.i
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bb14.i: ; preds = %bb14.i, %entry
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%i8.0.reg2mem.0.i = phi i32 [ 0, %entry ], [ %2, %bb14.i ] ; <i32> [#uses=1]
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%2 = add i32 %i8.0.reg2mem.0.i, 1 ; <i32> [#uses=2]
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%exitcond74.i = icmp eq i32 %2, 32 ; <i1> [#uses=1]
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br i1 %exitcond74.i, label %bb32.i, label %bb14.i
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bb32.i: ; preds = %bb32.i, %bb14.i
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%tmp.0.reg2mem.0.i = phi i32 [ %indvar.next63.i, %bb32.i ], [ 0, %bb14.i ] ; <i32> [#uses=1]
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%indvar.next63.i = add i32 %tmp.0.reg2mem.0.i, 1 ; <i32> [#uses=2]
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%exitcond64.i = icmp eq i32 %indvar.next63.i, 64 ; <i1> [#uses=1]
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br i1 %exitcond64.i, label %bb47.loopexit.i, label %bb32.i
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bb.i.i: ; preds = %bb47.loopexit.i
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unreachable
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stepsystem.exit.i: ; preds = %bb47.loopexit.i
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store %struct.node* null, %struct.node** %1, align 4
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br label %bb.i6.i
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bb.i6.i: ; preds = %bb.i6.i, %stepsystem.exit.i
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br i1 false, label %bb107.i.i, label %bb.i6.i
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bb107.i.i: ; preds = %bb107.i.i, %bb.i6.i
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%q_addr.0.i.i.in = phi %struct.bnode** [ null, %bb107.i.i ], [ %3, %bb.i6.i ] ; <%struct.bnode**> [#uses=0]
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br label %bb107.i.i
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bb47.loopexit.i: ; preds = %bb32.i
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%3 = getelementptr %struct.anon* %0, i32 0, i32 4, i32 0 ; <%struct.bnode**> [#uses=1]
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%4 = icmp eq %struct.node* null, null ; <i1> [#uses=1]
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br i1 %4, label %stepsystem.exit.i, label %bb.i.i
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}
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