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X86: Use btq for bit tests if the immediate can't be encoded in 32 bits.
Before: movabsq $4294967296, %rax ## encoding: [0x48,0xb8,0x00,0x00,0x00,0x00,0x01,0x00,0x00,0x00] testq %rax, %rdi ## encoding: [0x48,0x85,0xf8] jne LBB0_2 ## encoding: [0x75,A] After: btq $32, %rdi ## encoding: [0x48,0x0f,0xba,0xe7,0x20] jb LBB0_2 ## encoding: [0x72,A] btq is usually slower than testq because it doesn't fuse with the jump, but here we're better off saving one register and a giant movabsq. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145103 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -8543,11 +8543,19 @@ SDValue X86TargetLowering::LowerToBT(SDValue And, ISD::CondCode CC,
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}
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} else if (Op1.getOpcode() == ISD::Constant) {
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ConstantSDNode *AndRHS = cast<ConstantSDNode>(Op1);
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uint64_t AndRHSVal = AndRHS->getZExtValue();
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SDValue AndLHS = Op0;
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if (AndRHS->getZExtValue() == 1 && AndLHS.getOpcode() == ISD::SRL) {
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if (AndRHSVal == 1 && AndLHS.getOpcode() == ISD::SRL) {
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LHS = AndLHS.getOperand(0);
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RHS = AndLHS.getOperand(1);
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}
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// Use BT if the immediate can't be encoded in a TEST instruction.
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if (!isUInt<32>(AndRHSVal) && isPowerOf2_64(AndRHSVal)) {
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LHS = AndLHS;
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RHS = DAG.getConstant(Log2_64_Ceil(AndRHSVal), LHS.getValueType());
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}
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}
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if (LHS.getNode()) {
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35
test/CodeGen/X86/btq.ll
Normal file
35
test/CodeGen/X86/btq.ll
Normal file
@ -0,0 +1,35 @@
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; RUN: llc < %s -march=x86-64 | FileCheck %s
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declare void @bar()
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define void @test1(i64 %foo) nounwind {
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%and = and i64 %foo, 4294967296
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%tobool = icmp eq i64 %and, 0
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br i1 %tobool, label %if.end, label %if.then
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; CHECK: test1:
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; CHECK: btq $32
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if.then:
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tail call void @bar() nounwind
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br label %if.end
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if.end:
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ret void
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}
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define void @test2(i64 %foo) nounwind {
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%and = and i64 %foo, 2147483648
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%tobool = icmp eq i64 %and, 0
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br i1 %tobool, label %if.end, label %if.then
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; CHECK: test2:
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; CHECK: testl $-2147483648
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if.then:
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tail call void @bar() nounwind
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br label %if.end
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if.end:
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ret void
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}
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