[PATCH] D116735: [RISCV] Adjust RISCV data layout by using n32:64 in layout string

[Alex Bradbury via Phabricator via llvm-commits]

asb added a comment.

Thanks - I don't think much thought has gone into whether n32:n64 would be reasonable for RV64, so I really appreciate you digging in to it.

I've only run this against the GCC torture suite, and on average this seems to be about neutral (or mildly positive). There are a few cases where code is worse though - it's possible this is simply unmasking an issue with poor codegen for 32-bit types (that would otherwise be promoted earlier), though I haven't investigated. e.g.

  --- a/output_rv64imafdc_lp64_O1/930921-1.s
  +++ b/output_rv64imafdc_lp64_O1/930921-1.s
  @@ -24,18 +24,29 @@ main:                                   # @main
   # %bb.0:                                # %entry
          addi    sp, sp, -16
          sd      ra, 8(sp)                       # 8-byte Folded Spill
  +       li      a0, 0
          li      a1, 0
  -       li      a0, 1
  -       lui     a2, 2
  -       addiw   a2, a2, 1806
  +       lui     a2, 699051
  +       addiw   a2, a2, -1365
  +       slli    a6, a2, 32
  +       lui     a3, 171
  +       addiw   a3, a3, -1365
  +       slli    a3, a3, 12
  +       addi    a3, a3, -1365
  +       lui     a4, 2
  +       addiw   a4, a4, 1808
   .LBB1_1:                                # %for.body
                                           # =>This Inner Loop Header: Depth=1
  -       beqz    a0, .LBB1_4
  +       srli    a5, a0, 33
  +       slli    a2, a1, 32
  +       mulhu   a2, a2, a6
  +       srli    a2, a2, 33
  +       bne     a2, a5, .LBB1_4
   # %bb.2:                                # %for.cond
                                           #   in Loop: Header=BB1_1 Depth=1
  -       sext.w  a3, a1
          addiw   a1, a1, 1
  -       bgeu    a2, a3, .LBB1_1
  +       add     a0, a0, a3
  +       bne     a1, a4, .LBB1_1
   # %bb.3:                                # %for.end
          li      a0, 0
          call    exit


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D116735/new/

https://reviews.llvm.org/D116735