[PATCH 0/2] RISC-V: New pass to optimize calculation of offsets for memory operations.

[Manolis Tsamis <manolis.tsamis@vrull.eu>]

This pass tries to optimize memory offset calculations by moving them
from add immediate instructions to the memory loads/stores.
For example it can transform this:

  addi t4,sp,16
  add  t2,a6,t4
  shl  t3,t2,1
  ld   a2,0(t3)
  addi a2,1
  sd   a2,8(t2)

into the following (one instruction less):

  add  t2,a6,sp
  shl  t3,t2,1
  ld   a2,32(t3)
  addi a2,1
  sd   a2,24(t2)

Although there are places where this is done already, this pass is more
powerful and can handle the more difficult cases that are currently not
optimized. Also, it runs late enough and can optimize away unnecessary
stack pointer calculations.

The first patch in the series contains the implementation of this pass
while the second is a minor change that enables cprop_hardreg's
propgation of the stack pointer, because this pass depends on cprop
to do the propagation of optimized operations. If preferred I can split
this into two different patches (in which cases some of the testcases
included will fail temporarily).



Manolis Tsamis (2):
  Implementation of new RISCV optimizations pass: fold-mem-offsets.
  cprop_hardreg: Enable propagation of the stack pointer if possible.

 gcc/config.gcc                                |   2 +-
 gcc/config/riscv/riscv-fold-mem-offsets.cc    | 637 ++++++++++++++++++
 gcc/config/riscv/riscv-passes.def             |   1 +
 gcc/config/riscv/riscv-protos.h               |   1 +
 gcc/config/riscv/riscv.opt                    |   4 +
 gcc/config/riscv/t-riscv                      |   4 +
 gcc/doc/invoke.texi                           |   8 +
 gcc/regcprop.cc                               |   7 +-
 .../gcc.target/riscv/fold-mem-offsets-1.c     |  16 +
 .../gcc.target/riscv/fold-mem-offsets-2.c     |  24 +
 .../gcc.target/riscv/fold-mem-offsets-3.c     |  17 +
 11 files changed, 719 insertions(+), 2 deletions(-)
 create mode 100644 gcc/config/riscv/riscv-fold-mem-offsets.cc
 create mode 100644 gcc/testsuite/gcc.target/riscv/fold-mem-offsets-1.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/fold-mem-offsets-2.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/fold-mem-offsets-3.c

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2.34.1