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8bd004b033
sub-register indices and outputs a single super register which is formed from
a consecutive sequence of registers.
This is used as register allocation / coalescing aid and it is useful to
represent instructions that output register pairs / quads. For example,
v1024, v1025 = vload <address>
where v1024 and v1025 forms a register pair.
This really should be modelled as
v1024<3>, v1025<4> = vload <address>
but it would violate SSA property before register allocation is done.
Currently we use insert_subreg to form the super register:
v1026 = implicit_def
v1027 - insert_subreg v1026, v1024, 3
v1028 = insert_subreg v1027, v1025, 4
...
= use v1024
= use v1028
But this adds pseudo live interval overlap between v1024 and v1025.
We can now modeled it as
v1024, v1025 = vload <address>
v1026 = REG_SEQUENCE v1024, 3, v1025, 4
...
= use v1024
= use v1026
After coalescing, it will be
v1026<3>, v1025<4> = vload <address>
...
= use v1026<3>
= use v1026
llvm-svn: 102815
81 lines
3.3 KiB
C++
81 lines
3.3 KiB
C++
//===-- llvm/Target/TargetOpcodes.h - Target Indep Opcodes ------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the target independent instruction opcodes.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TARGET_TARGETOPCODES_H
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#define LLVM_TARGET_TARGETOPCODES_H
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namespace llvm {
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/// Invariant opcodes: All instruction sets have these as their low opcodes.
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namespace TargetOpcode {
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enum {
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PHI = 0,
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INLINEASM = 1,
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DBG_LABEL = 2,
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EH_LABEL = 3,
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GC_LABEL = 4,
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/// KILL - This instruction is a noop that is used only to adjust the
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/// liveness of registers. This can be useful when dealing with
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/// sub-registers.
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KILL = 5,
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/// EXTRACT_SUBREG - This instruction takes two operands: a register
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/// that has subregisters, and a subregister index. It returns the
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/// extracted subregister value. This is commonly used to implement
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/// truncation operations on target architectures which support it.
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EXTRACT_SUBREG = 6,
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/// INSERT_SUBREG - This instruction takes three operands: a register
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/// that has subregisters, a register providing an insert value, and a
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/// subregister index. It returns the value of the first register with
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/// the value of the second register inserted. The first register is
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/// often defined by an IMPLICIT_DEF, as is commonly used to implement
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/// anyext operations on target architectures which support it.
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INSERT_SUBREG = 7,
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/// IMPLICIT_DEF - This is the MachineInstr-level equivalent of undef.
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IMPLICIT_DEF = 8,
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/// SUBREG_TO_REG - This instruction is similar to INSERT_SUBREG except
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/// that the first operand is an immediate integer constant. This constant
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/// is often zero, as is commonly used to implement zext operations on
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/// target architectures which support it, such as with x86-64 (with
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/// zext from i32 to i64 via implicit zero-extension).
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SUBREG_TO_REG = 9,
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/// COPY_TO_REGCLASS - This instruction is a placeholder for a plain
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/// register-to-register copy into a specific register class. This is only
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/// used between instruction selection and MachineInstr creation, before
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/// virtual registers have been created for all the instructions, and it's
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/// only needed in cases where the register classes implied by the
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/// instructions are insufficient. The actual MachineInstrs to perform
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/// the copy are emitted with the TargetInstrInfo::copyRegToReg hook.
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COPY_TO_REGCLASS = 10,
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/// DBG_VALUE - a mapping of the llvm.dbg.value intrinsic
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DBG_VALUE = 11,
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/// REG_SEQUENCE - This variadic instruction is used to form a register that
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/// represent a consecutive sequence of sub-registers. It's used as register
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/// coalescing / allocation aid and must be eliminated before code emission.
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/// e.g. v1027 = REG_SEQUENCE v1024, 3, v1025, 4, v1026, 5
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/// After register coalescing references of v1024 should be replace with
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/// v1027:3, v1025 with v1027:4, etc.
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REG_SEQUENCE = 12
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};
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} // end namespace TargetOpcode
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} // end namespace llvm
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#endif
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