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8265917: Different values computed by C2 and interpreter/C1 for Math.pow(x, 2.0) on x86_32
Reviewed-by: kvn, thartmann
1 parent e144104 commit 889d246

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src/hotspot/cpu/x86/macroAssembler_x86_pow.cpp

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Original file line numberDiff line numberDiff line change
@@ -2515,6 +2515,8 @@ ATTRIBUTE_ALIGNED(16) juint _static_const_table_pow[] =
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};
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ATTRIBUTE_ALIGNED(8) double _DOUBLE2 = 2.0;
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//registers,
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// input: xmm0, xmm1
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// scratch: xmm1, xmm2, xmm3, xmm4, xmm5, xmm6, xmm7
@@ -2538,17 +2540,28 @@ void MacroAssembler::fast_pow(XMMRegister xmm0, XMMRegister xmm1, XMMRegister xm
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Label L_2TAG_PACKET_48_0_2, L_2TAG_PACKET_49_0_2, L_2TAG_PACKET_50_0_2, L_2TAG_PACKET_51_0_2;
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Label L_2TAG_PACKET_52_0_2, L_2TAG_PACKET_53_0_2, L_2TAG_PACKET_54_0_2, L_2TAG_PACKET_55_0_2;
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Label L_2TAG_PACKET_56_0_2, L_2TAG_PACKET_57_0_2, L_2TAG_PACKET_58_0_2, start;
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Label L_NOT_DOUBLE2;
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assert_different_registers(tmp, eax, ecx, edx);
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address static_const_table_pow = (address)_static_const_table_pow;
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address DOUBLE2 = (address) &_DOUBLE2;
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bind(start);
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subl(rsp, 120);
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movl(Address(rsp, 64), tmp);
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lea(tmp, ExternalAddress(static_const_table_pow));
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movsd(xmm0, Address(rsp, 128));
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movsd(xmm1, Address(rsp, 136));
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// Special case: pow(x, 2.0) => x * x
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ucomisd(xmm1, ExternalAddress(DOUBLE2));
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jccb(Assembler::notEqual, L_NOT_DOUBLE2);
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jccb(Assembler::parity, L_NOT_DOUBLE2);
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mulsd(xmm0, xmm0);
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jmp(L_2TAG_PACKET_21_0_2);
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bind(L_NOT_DOUBLE2);
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xorpd(xmm2, xmm2);
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movl(eax, 16368);
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pinsrw(xmm2, eax, 3);
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,53 @@
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/*
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* Copyright (C) 2021 THL A29 Limited, a Tencent company. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* @test
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* @bug 8265917
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* @summary test the optimization of pow(x, 2.0)
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* @run main/othervm TestPow2Opt
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* @run main/othervm -Xint TestPow2Opt
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* @run main/othervm -Xbatch -XX:TieredStopAtLevel=1 TestPow2Opt
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* @run main/othervm -Xbatch -XX:-TieredCompilation TestPow2Opt
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*/
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public class TestPow2Opt {
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static void test(double a) {
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double r1 = a * a;
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double r2 = Math.pow(a, 2.0);
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if (r1 != r2) {
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throw new RuntimeException("pow(" + a + ", 2.0), expected: " + r1 + ", actual: " + r2);
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}
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}
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public static void main(String[] args) throws Exception {
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for (int i = 0; i < 10; i++) {
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for (int j = 1; j < 100000; j++) {
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test(j * 1.0);
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test(1.0 / j);
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}
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}
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}
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}

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