diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Target/X86/X86Instr64bit.td | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/llvm/lib/Target/X86/X86Instr64bit.td b/llvm/lib/Target/X86/X86Instr64bit.td index 0babaa46f2d..dc15e4aa4ee 100644 --- a/llvm/lib/Target/X86/X86Instr64bit.td +++ b/llvm/lib/Target/X86/X86Instr64bit.td @@ -1588,11 +1588,11 @@ def : Pat<(i8 (trunc GR16:$src)), Requires<[In64BitMode]>; // h-register tricks. -// For now, be conservative and only the extract if the value is immediately -// zero-extended or stored, which are somewhat common cases. This uses a bunch -// of code to prevent a register requiring a REX prefix from being allocated in -// the same instruction as the h register, as there's currently no way to -// describe this requirement to the register allocator. +// For now, be conservative on x86-64 and use an h-register extract only if the +// value is immediately zero-extended or stored, which are somewhat common +// cases. This uses a bunch of code to prevent a register requiring a REX prefix +// from being allocated in the same instruction as the h register, as there's +// currently no way to describe this requirement to the register allocator. // h-register extract and zero-extend. def : Pat<(and (srl_su GR64:$src, (i8 8)), (i64 255)), |
