replacement of multiple values. This is slightly more efficient
than doing multiple ReplaceAllUsesOfValueWith calls, and theoretically
could be optimized even further. However, an important property of this
new function is that it handles the case where the source value set and
destination value set overlap. This makes it feasible for isel to use
SelectNodeTo in many very common cases, which is advantageous because
SelectNodeTo avoids a temporary node and it doesn't require CSEMap
updates for users of values that don't change position.
Revamp MorphNodeTo, which is what does all the work of SelectNodeTo, to
handle operand lists more efficiently, and to correctly handle a number
of corner cases to which its new wider use exposes it.
This commit also includes a change to the encoding of post-isel opcodes
in SDNodes; now instead of being sandwiched between the target-independent
pre-isel opcodes and the target-dependent pre-isel opcodes, post-isel
opcodes are now represented as negative values. This makes it possible
to test if an opcode is pre-isel or post-isel without having to know
the size of the current target's post-isel instruction set.
These changes speed up llc overall by 3% and reduce memory usage by 10%
on the InstructionCombining.cpp testcase with -fast and -regalloc=local.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53728 91177308-0d34-0410-b5e6-96231b3b80d8
A brief description about PIC16:
===============================
PIC16 is an 8-bit microcontroller with only one 8-bit register which is the
accumulator. All arithmetic/load/store operations are 8-bit only.
The architecture has two address spaces: program and data. The program memory
is divided into 2K pages and the data memory is divided into banks of 128 byte, with only 80 usable bytes, resulting in an non-contiguous data memory.
It supports direct data memory access (by specifying the address as part of the instruction) and indirect data and program memory access (in an unorthodox fashion which utilize a 16 bit pointer register).
Two classes of registers exist: (8-bit class which is only one
accumulator) (16-bit class, which contains one or more 16 bit
pointer(s))
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51027 91177308-0d34-0410-b5e6-96231b3b80d8
