else
{
MakeSrcContained(tree, shiftBy);
- }
- // Codegen of shift oper sets ZF and SF flags.
- // Note that Rotate Left/Right instructions don't set ZF and SF flags.
- if (tree->OperIsShift())
- {
- tree->gtFlags |= GTF_ZSF_SET;
+ // Note that Rotate Left/Right instructions don't set ZF and SF flags.
+ //
+ // If the operand being shifted is 32-bits then upper three bits are masked
+ // by hardware to get actual shift count. Similarly for 64-bit operands
+ // shift count is narrowed to [0..63]. If the resulting shift count is zero,
+ // then shift operation won't modify flags.
+ //
+ // TODO-CQ-XARCH: We can optimize generating 'test' instruction for GT_EQ/NE(shift, 0)
+ // if the shift count is known to be non-zero and in the range depending on the
+ // operand size.
}
}
--- /dev/null
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace bug
+{
+ class Program
+ {
+ static int Pass = 100;
+ static int Fail = -1;
+
+ // This test is meant to check that in case of
+ // GT_EQ/NE(shift, 0), JIT doesn't optimize out
+ // 'test' instruction incorrectly, because shift
+ // operations on xarch don't modify flags if the
+ // shift count is zero.
+ static int Main(string[] args)
+ {
+ // Absolute bits
+ int bitCount = 0;
+ while ((0 != (100 >> bitCount)) && (31 > bitCount))
+ {
+ bitCount++;
+ }
+ // Sign bit
+ bitCount++;
+
+ if (bitCount != 8)
+ {
+ return Fail;
+ }
+
+ return Pass;
+ }
+ }
+}
--- /dev/null
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+ <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
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+ <CodeAnalysisDependentAssemblyPaths Condition=" '$(VS100COMNTOOLS)' != '' " Include="$(VS100COMNTOOLS)..\IDE\PrivateAssemblies">
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+ <DebugType></DebugType>
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+ <ItemGroup>
+ <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />
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+ <ProjectJson>$(JitPackagesConfigFileDirectory)minimal\project.json</ProjectJson>
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