Split edges to have a block to add regmove & copy instructions.

When using basic block instructions cannot be added in-between jump instructions which are ending basic blocks. These changes create extra basic blocks such that extra space is available for the spilling and moving registers where they are expected.
This commit is contained in:
Nicolas B. Pierron
2019-08-30 18:44:35 +02:00
committed by GitHub
parent bb87f1a54a
commit 381578311c
10 changed files with 529 additions and 3 deletions

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test regalloc
target riscv32
feature "basic-blocks"
; Test the coalescer.
; regex: V=v\d+
; regex: WS=\s+
; regex: LOC=%\w+
; regex: EBB=ebb\d+
; This function is already CSSA, so no copies should be inserted.
function %cssa(i32) -> i32 {
ebb0(v0: i32):
; not: copy
; v0 is used by the branch and passed as an arg - that's no conflict.
brnz v0, ebb1(v0)
jump ebb2
ebb2:
; v0 is live across the branch above. That's no conflict.
v1 = iadd_imm v0, 7
jump ebb1(v1)
ebb1(v10: i32):
v11 = iadd_imm v10, 7
return v11
}
function %trivial(i32) -> i32 {
ebb0(v0: i32):
; check: brnz v0, $(splitEdge=$EBB)
brnz v0, ebb1(v0)
jump ebb2
ebb2:
; not: copy
v1 = iadd_imm v0, 7
jump ebb1(v1)
; check: $splitEdge:
; nextln: $(cp1=$V) = copy.i32 v0
; nextln: jump ebb1($cp1)
ebb1(v10: i32):
; Use v0 in the destination EBB causes a conflict.
v11 = iadd v10, v0
return v11
}
; A value is used as an SSA argument twice in the same branch.
function %dualuse(i32) -> i32 {
ebb0(v0: i32):
; check: brnz v0, $(splitEdge=$EBB)
brnz v0, ebb1(v0, v0)
jump ebb2
ebb2:
v1 = iadd_imm v0, 7
v2 = iadd_imm v1, 56
jump ebb1(v1, v2)
; check: $splitEdge:
; check: $(cp1=$V) = copy.i32 v0
; nextln: jump ebb1($cp1, v0)
ebb1(v10: i32, v11: i32):
v12 = iadd v10, v11
return v12
}
; Interference away from the branch
; The interference can be broken with a copy at either branch.
function %interference(i32) -> i32 {
ebb0(v0: i32):
; not: copy
; check: brnz v0, $(splitEdge=$EBB)
; not: copy
brnz v0, ebb1(v0)
jump ebb2
ebb2:
v1 = iadd_imm v0, 7
; v1 and v0 interfere here:
v2 = iadd_imm v0, 8
; check: $(cp0=$V) = copy v1
; check: jump ebb1($cp0)
jump ebb1(v1)
; check: $splitEdge:
; not: copy
; nextln: jump ebb1(v0)
ebb1(v10: i32):
; not: copy
v11 = iadd_imm v10, 7
return v11
}
; A loop where one induction variable is used as a backedge argument.
function %fibonacci(i32) -> i32 {
ebb0(v0: i32):
v1 = iconst.i32 1
v2 = iconst.i32 2
jump ebb1(v1, v2)
ebb1(v10: i32, v11: i32):
; v11 needs to be isolated because it interferes with v10.
; check: ebb1(v10: i32 [$LOC], $(nv11a=$V): i32 [$LOC])
; check: v11 = copy $nv11a
v12 = iadd v10, v11
v13 = icmp ult v12, v0
; check: brnz v13, $(splitEdge=$EBB)
brnz v13, ebb1(v11, v12)
jump ebb2
; check: $splitEdge:
; check: $(nv11b=$V) = copy.i32 v11
; not: copy
; check: jump ebb1($nv11b, v12)
ebb2:
return v12
}
; Function arguments passed on the stack aren't allowed to be part of a virtual
; register, at least for now. This is because the other values in the virtual
; register would need to be spilled to the incoming_arg stack slot which we treat
; as belonging to the caller.
function %stackarg(i32, i32, i32, i32, i32, i32, i32, i32, i32) -> i32 {
; check: ss0 = incoming_arg 4
; not: incoming_arg
ebb0(v0: i32, v1: i32, v2: i32, v3: i32, v4: i32, v5: i32, v6: i32, v7: i32, v8: i32):
; check: fill v8
; not: v8
jump ebb1(v8)
ebb1(v10: i32):
v11 = iadd_imm v10, 1
return v11
}
function %gvn_unremovable_phi(i32) system_v {
ebb0(v0: i32):
v2 = iconst.i32 0
jump ebb2(v2, v0)
ebb2(v3: i32, v4: i32):
brnz v3, ebb2(v3, v4)
jump ebb3
ebb3:
v5 = iconst.i32 1
brnz v3, ebb2(v2, v5)
jump ebb4
ebb4:
return
}

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test regalloc
target riscv32
feature !"basic-blocks"
; Test the coalescer.
; regex: V=v\d+

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test regalloc
target x86_64 haswell
feature "basic-blocks"
; regex: V=v\d+
; regex: EBB=ebb\d+
; Filed as https://github.com/CraneStation/cranelift/issues/208
;
; The verifier complains about a branch argument that is not in the same virtual register as the
; corresponding EBB argument.
;
; The problem was the reload pass rewriting EBB arguments on "brnz v9, ebb3(v9)"
function %pr208(i64 vmctx [%rdi]) system_v {
gv1 = vmctx
gv0 = iadd_imm.i64 gv1, -8
heap0 = static gv0, min 0, bound 0x5000, offset_guard 0x0040_0000
sig0 = (i64 vmctx [%rdi]) -> i32 [%rax] system_v
sig1 = (i64 vmctx [%rdi], i32 [%rsi]) system_v
fn0 = u0:1 sig0
fn1 = u0:3 sig1
ebb0(v0: i64):
v1 = iconst.i32 0
v2 = call fn0(v0)
v20 = iconst.i32 0x4ffe
v16 = icmp uge v2, v20
brz v16, ebb5
jump ebb9
ebb9:
trap heap_oob
ebb5:
v17 = uextend.i64 v2
v18 = iadd_imm.i64 v0, -8
v19 = load.i64 v18
v3 = iadd v19, v17
v4 = load.i32 v3
v21 = iconst.i32 0
v5 = icmp eq v4, v21
v6 = bint.i32 v5
brnz v6, ebb2
jump ebb3(v4)
ebb3(v7: i32):
call fn1(v0, v7)
v26 = iconst.i32 0x4ffe
v22 = icmp uge v7, v26
brz v22, ebb6
jump ebb10
ebb10:
trap heap_oob
ebb6:
v23 = uextend.i64 v7
v24 = iadd_imm.i64 v0, -8
v25 = load.i64 v24
v8 = iadd v25, v23
v9 = load.i32 v8+56
; check: v9 = spill
; check: brnz $V, $(splitEdge=$EBB)
brnz v9, ebb3(v9)
jump ebb4
; check: $splitEdge:
; nextln: jump ebb3(v9)
ebb4:
jump ebb2
ebb2:
v10 = iconst.i32 0
v31 = iconst.i32 0x4ffe
v27 = icmp uge v10, v31
brz v27, ebb7
jump ebb11
ebb11:
trap heap_oob
ebb7:
v28 = uextend.i64 v10
v29 = iadd_imm.i64 v0, -8
v30 = load.i64 v29
v11 = iadd v30, v28
v12 = load.i32 v11+12
call fn1(v0, v12)
v13 = iconst.i32 0
v36 = iconst.i32 0x4ffe
v32 = icmp uge v13, v36
brz v32, ebb8
jump ebb12
ebb12:
trap heap_oob
ebb8:
v33 = uextend.i64 v13
v34 = iadd_imm.i64 v0, -8
v35 = load.i64 v34
v14 = iadd v35, v33
v15 = load.i32 v14+12
call fn1(v0, v15)
jump ebb1
ebb1:
return
}

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test regalloc
target x86_64 haswell
feature !"basic-blocks"
; regex: V=v\d+

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test regalloc
target i686
feature "basic-blocks"
; regex: V=v\d+
; regex: EBB=ebb\d+
; The value v9 appears both as the branch control and one of the EBB arguments
; in the brnz instruction in ebb2. It also happens that v7 and v9 are assigned
; to the same register, so v9 doesn't need to be moved before the brnz.
;
; This ended up confusong the constraint solver which had not made a record of
; the fixed register assignment for v9 since it was already in the correct
; register.
function %pr147(i32) -> i32 system_v {
ebb0(v0: i32):
v1 = iconst.i32 0
v2 = iconst.i32 1
v3 = iconst.i32 0
jump ebb2(v3, v2, v0)
ebb2(v4: i32, v5: i32, v7: i32):
; check: ebb2
v6 = iadd v4, v5
v8 = iconst.i32 -1
; v7 is killed here and v9 gets the same register.
v9 = iadd v7, v8
; check: v9 = iadd v7, v8
; Here v9 the brnz control appears to interfere with v9 the EBB argument,
; so divert_fixed_input_conflicts() calls add_var(v9), which is ok. The
; add_var sanity checks got confused when no fixed assignment could be
; found for v9.
;
; We should be able to handle this situation without making copies of v9.
brnz v9, ebb2(v5, v6, v9)
; check: brnz v9, $(splitEdge=$EBB)
jump ebb3
; check: $splitEdge:
; check: jump ebb2($V, $V, v9)
ebb3:
return v5
}
function %select_i64(i64, i64, i32) -> i64 {
ebb0(v0: i64, v1: i64, v2: i32):
v3 = select v2, v0, v1
return v3
}

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@@ -1,6 +1,6 @@
test regalloc
target i686
feature !"basic-blocks"
; regex: V=v\d+