On Nehalem and newer CPUs there is a 2 cycle latency penalty on using a register
in a different domain than where it was defined. Some instructions have
equvivalents for different domains, like por/orps/orpd.
The SSEDomainFix pass tries to minimize the number of domain crossings by
changing between equvivalent opcodes where possible.
This is a work in progress, in particular the pass doesn't do anything yet. SSE
instructions are tagged with their execution domain in TableGen using the last
two bits of TSFlags. Note that not all instructions are tagged correctly. Life
just isn't that simple.
The SSE execution domain issue is very similar to the ARM NEON/VFP pipeline
issue handled by NEONMoveFixPass. This pass may become target independent to
handle both.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@99524 91177308-0d34-0410-b5e6-96231b3b80d8
This is work in progress. So far, SSE execution domain tables are added to
X86InstrInfo, and a skeleton pass is enabled with -sse-domain-fix.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@99345 91177308-0d34-0410-b5e6-96231b3b80d8
- Although it would be nice to allow this decoupling, the assembler needs to be able to reason about MCSymbolRefExprs in too many places to make this viable. We can use a target specific encoding of the variant if this becomes an issue.
- This patch also extends llvm-mc to support parsing of the modifiers, as opposed to lumping them in with the symbol.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98592 91177308-0d34-0410-b5e6-96231b3b80d8
incarnations), integrated into the MC framework.
The disassembler is table-driven, using a custom TableGen backend to
generate hierarchical tables optimized for fast decode. The disassembler
consumes MemoryObjects and produces arrays of MCInsts, adhering to the
abstract base class MCDisassembler (llvm/MC/MCDisassembler.h).
The disassembler is documented in detail in
- lib/Target/X86/Disassembler/X86Disassembler.cpp (disassembler runtime)
- utils/TableGen/DisassemblerEmitter.cpp (table emitter)
You can test the disassembler by running llvm-mc -disassemble for i386
or x86_64 targets. Please let me know if you encounter any problems
with it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91749 91177308-0d34-0410-b5e6-96231b3b80d8
special-purpose hook to a new pass. Also, add check to see if any
x87 virtual registers are used, to avoid doing any work in the
common case that no x87 code is needed.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@59190 91177308-0d34-0410-b5e6-96231b3b80d8
