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Fix the "test" optimization to recognize "dec" as an add of
negative one, as subtracts of immediates are canonicalized to adds. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66180 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -5382,13 +5382,19 @@ SDValue X86TargetLowering::EmitTest(SDValue Op, SelectionDAG &DAG) {
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UE = Op.getNode()->use_end(); UI != UE; ++UI)
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if (UI->getOpcode() == ISD::STORE)
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goto default_case;
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// An add of one will be selected as an INC.
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if (ConstantSDNode *C =
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dyn_cast<ConstantSDNode>(Op.getNode()->getOperand(1)))
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dyn_cast<ConstantSDNode>(Op.getNode()->getOperand(1))) {
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// An add of one will be selected as an INC.
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if (C->getAPIntValue() == 1) {
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Opcode = X86ISD::INC;
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break;
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}
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// An add of negative one (subtract of one) will be selected as a DEC.
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if (C->getAPIntValue().isAllOnesValue()) {
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Opcode = X86ISD::DEC;
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break;
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}
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}
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// Otherwise use a regular EFLAGS-setting add.
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Opcode = X86ISD::ADD;
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break;
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@ -5399,13 +5405,6 @@ SDValue X86TargetLowering::EmitTest(SDValue Op, SelectionDAG &DAG) {
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UE = Op.getNode()->use_end(); UI != UE; ++UI)
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if (UI->getOpcode() == ISD::STORE)
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goto default_case;
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// A subtract of one will be selected as a DEC.
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if (ConstantSDNode *C =
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dyn_cast<ConstantSDNode>(Op.getNode()->getOperand(1)))
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if (C->getAPIntValue() == 1) {
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Opcode = X86ISD::DEC;
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break;
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}
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// Otherwise use a regular EFLAGS-setting sub.
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Opcode = X86ISD::SUB;
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break;
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23
test/CodeGen/X86/peep-test-1.ll
Normal file
23
test/CodeGen/X86/peep-test-1.ll
Normal file
@ -0,0 +1,23 @@
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; RUN: llvm-as < %s | llc -march=x86 > %t
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; RUN: grep dec %t | count 1
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; RUN: not grep test %t
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; RUN: not grep cmp %t
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define void @foo(i32 %n, double* nocapture %p) nounwind {
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br label %bb
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bb:
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%indvar = phi i32 [ 0, %0 ], [ %indvar.next, %bb ]
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%i.03 = sub i32 %n, %indvar
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%1 = getelementptr double* %p, i32 %i.03
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%2 = load double* %1, align 4
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%3 = mul double %2, 2.930000e+00
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store double %3, double* %1, align 4
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%4 = add i32 %i.03, -1
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%phitmp = icmp slt i32 %4, 0
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%indvar.next = add i32 %indvar, 1
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br i1 %phitmp, label %bb, label %return
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return:
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ret void
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}
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