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x86: Fix redundant compare elimination
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Redundant compare elimination is a code
generation optimization that attempts to drop
redundant compare instructions before a jump.
This can happen when the the previous
instruction sets condition code flags and is
compared with 0. However, some instructions
such as DIV and IDIV can modify these flags
in undefined ways. This commit lets the code
the code generator know that these instructions
may modify condition code flags. In addition,
the code generator should check if the
instruction that modifies these flags belongs
to the expected node.

Fixes: eclipse-openj9/openj9#17496

Signed-off-by: Bradley Wood <bradley.wood@ibm.com>
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BradleyWood committed Jun 5, 2023
1 parent 283d187 commit 0478a92
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Showing 2 changed files with 15 additions and 12 deletions.
3 changes: 3 additions & 0 deletions compiler/x/codegen/ControlFlowEvaluator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -220,6 +220,9 @@ bool isConditionCodeSetForCompareToZero(TR::Node *node, bool justTestZeroFlag)
return false;
}

if (prevInstr->getOpCode().modifiesSomeArithmeticFlags() && prevInstr->getNode() != node)
return false;

return true;
}
}
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24 changes: 12 additions & 12 deletions compiler/x/codegen/X86Ops.ins
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Original file line number Diff line number Diff line change
Expand Up @@ -1884,62 +1884,62 @@ INSTRUCTION(FXCHReg, fxch,
FEATURES(0)),
INSTRUCTION(IDIV1AccReg, idiv,
BINARY(VEX_L___, VEX_vNONE, PREFIX___, REX__, ESCAPE_____, 0xf6, 7, ModRM_EXT_, Immediate_0),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_SourceRegisterInModRM | IA32OpProp_TargetRegisterIgnored | IA32OpProp_ByteSource | IA32OpProp_ByteTarget | IA32OpProp_UsesTarget),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_SourceRegisterInModRM | IA32OpProp_TargetRegisterIgnored | IA32OpProp_ByteSource | IA32OpProp_ByteTarget | IA32OpProp_UsesTarget | IA32OpProp_ModifiesOverflowFlag | IA32OpProp_ModifiesSignFlag | IA32OpProp_ModifiesZeroFlag | IA32OpProp_ModifiesParityFlag | IA32OpProp_ModifiesCarryFlag),
PROPERTY1(IA32OpProp1_TargetRegIsImplicit),
FEATURES(0)),
INSTRUCTION(IDIV2AccReg, idiv,
BINARY(VEX_L___, VEX_vNONE, PREFIX_66, REX__, ESCAPE_____, 0xf7, 7, ModRM_EXT_, Immediate_0),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_SourceRegisterInModRM | IA32OpProp_TargetRegisterIgnored | IA32OpProp_ShortSource | IA32OpProp_ShortTarget | IA32OpProp_UsesTarget),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_SourceRegisterInModRM | IA32OpProp_TargetRegisterIgnored | IA32OpProp_ShortSource | IA32OpProp_ShortTarget | IA32OpProp_UsesTarget | IA32OpProp_ModifiesOverflowFlag | IA32OpProp_ModifiesSignFlag | IA32OpProp_ModifiesZeroFlag | IA32OpProp_ModifiesParityFlag | IA32OpProp_ModifiesCarryFlag),
PROPERTY1(IA32OpProp1_TargetRegIsImplicit),
FEATURES(0)),
INSTRUCTION(IDIV4AccReg, idiv,
BINARY(VEX_L___, VEX_vNONE, PREFIX___, REX__, ESCAPE_____, 0xf7, 7, ModRM_EXT_, Immediate_0),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_SourceRegisterInModRM | IA32OpProp_TargetRegisterIgnored | IA32OpProp_IntSource | IA32OpProp_IntTarget | IA32OpProp_UsesTarget),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_SourceRegisterInModRM | IA32OpProp_TargetRegisterIgnored | IA32OpProp_IntSource | IA32OpProp_IntTarget | IA32OpProp_UsesTarget | IA32OpProp_ModifiesOverflowFlag | IA32OpProp_ModifiesSignFlag | IA32OpProp_ModifiesZeroFlag | IA32OpProp_ModifiesParityFlag | IA32OpProp_ModifiesCarryFlag),
PROPERTY1(IA32OpProp1_TargetRegIsImplicit),
FEATURES(0)),
INSTRUCTION(IDIV8AccReg, idiv,
BINARY(VEX_L___, VEX_vNONE, PREFIX___, REX_W, ESCAPE_____, 0xf7, 7, ModRM_EXT_, Immediate_0),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_SourceRegisterInModRM | IA32OpProp_TargetRegisterIgnored | IA32OpProp_UsesTarget),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_SourceRegisterInModRM | IA32OpProp_TargetRegisterIgnored | IA32OpProp_UsesTarget | IA32OpProp_ModifiesOverflowFlag | IA32OpProp_ModifiesSignFlag | IA32OpProp_ModifiesZeroFlag | IA32OpProp_ModifiesParityFlag | IA32OpProp_ModifiesCarryFlag),
PROPERTY1(IA32OpProp1_LongSource | IA32OpProp1_LongTarget | IA32OpProp1_TargetRegIsImplicit),
FEATURES(0)),
INSTRUCTION(DIV4AccReg, div,
BINARY(VEX_L___, VEX_vNONE, PREFIX___, REX__, ESCAPE_____, 0xf7, 6, ModRM_EXT_, Immediate_0),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_SourceRegisterInModRM | IA32OpProp_TargetRegisterIgnored | IA32OpProp_IntSource | IA32OpProp_IntTarget | IA32OpProp_UsesTarget),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_SourceRegisterInModRM | IA32OpProp_TargetRegisterIgnored | IA32OpProp_IntSource | IA32OpProp_IntTarget | IA32OpProp_UsesTarget | IA32OpProp_ModifiesOverflowFlag | IA32OpProp_ModifiesSignFlag | IA32OpProp_ModifiesZeroFlag | IA32OpProp_ModifiesParityFlag | IA32OpProp_ModifiesCarryFlag),
PROPERTY1(0),
FEATURES(0)),
INSTRUCTION(DIV8AccReg, div,
BINARY(VEX_L___, VEX_vNONE, PREFIX___, REX_W, ESCAPE_____, 0xf7, 6, ModRM_EXT_, Immediate_0),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_SourceRegisterInModRM | IA32OpProp_TargetRegisterIgnored | IA32OpProp_UsesTarget),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_SourceRegisterInModRM | IA32OpProp_TargetRegisterIgnored | IA32OpProp_UsesTarget | IA32OpProp_ModifiesOverflowFlag | IA32OpProp_ModifiesSignFlag | IA32OpProp_ModifiesZeroFlag | IA32OpProp_ModifiesParityFlag | IA32OpProp_ModifiesCarryFlag),
PROPERTY1(IA32OpProp1_LongSource | IA32OpProp1_LongTarget),
FEATURES(0)),
INSTRUCTION(IDIV1AccMem, idiv,
BINARY(VEX_L___, VEX_vNONE, PREFIX___, REX__, ESCAPE_____, 0xf6, 7, ModRM_EXT_, Immediate_0),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_TargetRegisterIgnored | IA32OpProp_ByteSource | IA32OpProp_ByteTarget | IA32OpProp_UsesTarget),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_TargetRegisterIgnored | IA32OpProp_ByteSource | IA32OpProp_ByteTarget | IA32OpProp_UsesTarget | IA32OpProp_ModifiesOverflowFlag | IA32OpProp_ModifiesSignFlag | IA32OpProp_ModifiesZeroFlag | IA32OpProp_ModifiesParityFlag | IA32OpProp_ModifiesCarryFlag),
PROPERTY1(IA32OpProp1_SourceIsMemRef | IA32OpProp1_TargetRegIsImplicit),
FEATURES(0)),
INSTRUCTION(IDIV2AccMem, idiv,
BINARY(VEX_L___, VEX_vNONE, PREFIX_66, REX__, ESCAPE_____, 0xf7, 7, ModRM_EXT_, Immediate_0),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_TargetRegisterIgnored | IA32OpProp_ShortSource | IA32OpProp_ShortTarget | IA32OpProp_UsesTarget),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_TargetRegisterIgnored | IA32OpProp_ShortSource | IA32OpProp_ShortTarget | IA32OpProp_UsesTarget | IA32OpProp_ModifiesOverflowFlag | IA32OpProp_ModifiesSignFlag | IA32OpProp_ModifiesZeroFlag | IA32OpProp_ModifiesParityFlag | IA32OpProp_ModifiesCarryFlag),
PROPERTY1(IA32OpProp1_SourceIsMemRef | IA32OpProp1_TargetRegIsImplicit),
FEATURES(0)),
INSTRUCTION(IDIV4AccMem, idiv,
BINARY(VEX_L___, VEX_vNONE, PREFIX___, REX__, ESCAPE_____, 0xf7, 7, ModRM_EXT_, Immediate_0),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_TargetRegisterIgnored | IA32OpProp_IntSource | IA32OpProp_IntTarget | IA32OpProp_UsesTarget),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_TargetRegisterIgnored | IA32OpProp_IntSource | IA32OpProp_IntTarget | IA32OpProp_UsesTarget | IA32OpProp_ModifiesOverflowFlag | IA32OpProp_ModifiesSignFlag | IA32OpProp_ModifiesZeroFlag | IA32OpProp_ModifiesParityFlag | IA32OpProp_ModifiesCarryFlag),
PROPERTY1(IA32OpProp1_SourceIsMemRef | IA32OpProp1_TargetRegIsImplicit),
FEATURES(0)),
INSTRUCTION(IDIV8AccMem, idiv,
BINARY(VEX_L___, VEX_vNONE, PREFIX___, REX_W, ESCAPE_____, 0xf7, 7, ModRM_EXT_, Immediate_0),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_TargetRegisterIgnored | IA32OpProp_UsesTarget),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_TargetRegisterIgnored | IA32OpProp_UsesTarget | IA32OpProp_ModifiesOverflowFlag | IA32OpProp_ModifiesSignFlag | IA32OpProp_ModifiesZeroFlag | IA32OpProp_ModifiesParityFlag | IA32OpProp_ModifiesCarryFlag),
PROPERTY1(IA32OpProp1_LongSource | IA32OpProp1_LongTarget | IA32OpProp1_SourceIsMemRef | IA32OpProp1_TargetRegIsImplicit),
FEATURES(0)),
INSTRUCTION(DIV4AccMem, div,
BINARY(VEX_L___, VEX_vNONE, PREFIX___, REX__, ESCAPE_____, 0xf7, 6, ModRM_EXT_, Immediate_0),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_TargetRegisterIgnored | IA32OpProp_IntSource | IA32OpProp_IntTarget | IA32OpProp_UsesTarget),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_TargetRegisterIgnored | IA32OpProp_IntSource | IA32OpProp_IntTarget | IA32OpProp_UsesTarget | IA32OpProp_ModifiesOverflowFlag | IA32OpProp_ModifiesSignFlag | IA32OpProp_ModifiesZeroFlag | IA32OpProp_ModifiesParityFlag | IA32OpProp_ModifiesCarryFlag),
PROPERTY1(IA32OpProp1_SourceIsMemRef),
FEATURES(0)),
INSTRUCTION(DIV8AccMem, div,
BINARY(VEX_L___, VEX_vNONE, PREFIX___, REX_W, ESCAPE_____, 0xf7, 6, ModRM_EXT_, Immediate_0),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_TargetRegisterIgnored | IA32OpProp_UsesTarget),
PROPERTY0(IA32OpProp_ModifiesTarget | IA32OpProp_TargetRegisterIgnored | IA32OpProp_UsesTarget | IA32OpProp_ModifiesOverflowFlag | IA32OpProp_ModifiesSignFlag | IA32OpProp_ModifiesZeroFlag | IA32OpProp_ModifiesParityFlag | IA32OpProp_ModifiesCarryFlag),
PROPERTY1(IA32OpProp1_LongSource | IA32OpProp1_LongTarget | IA32OpProp1_SourceIsMemRef),
FEATURES(0)),
INSTRUCTION(DIVSSRegReg, divss,
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