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go/test/fixedbugs/bug385_64.go
Than McIntosh 875332b8a2 cmd/compile/internal: merge stack slots for selected local auto vars
[This is a partial roll-forward of CL 553055, the main change here
is that the stack slot overlap operation is flagged off by default
(can be enabled by hand with -gcflags=-d=mergelocals=1) ]

Preliminary compiler support for merging/overlapping stack slots of
local variables whose access patterns are disjoint.

This patch includes changes in AllocFrame to do the actual
merging/overlapping based on information returned from a new
liveness.MergeLocals helper. The MergeLocals helper identifies
candidates by looking for sets of AUTO variables that either A) have
the same size and GC shape (if types contain pointers), or B) have the
same size (but potentially different types as long as those types have
no pointers). Variables must be greater than (3*types.PtrSize) in size
to be considered for merging.

After forming candidates, MergeLocals collects variables into "can be
overlapped" equivalence classes or partitions; this process is driven
by an additional liveness analysis pass. Ideally it would be nice to
move the existing stackmap liveness pass up before AllocFrame
and "widen" it to include merge candidates so that we can do just a
single liveness as opposed to two passes, however this may be difficult
given that the merge-locals liveness has to take into account
writes corresponding to dead stores.

This patch also required a change to the way ssa.OpVarDef pseudo-ops
are generated; prior to this point they would only be created for
variables whose type included pointers; if stack slot merging is
enabled then the ssagen code creates OpVarDef ops for all auto vars
that are merge candidates.

Note that some temporaries created late in the compilation process
(e.g. during ssa backend) are difficult to reason about, especially in
cases where we take the address of a temp and pass it to the runtime.
For the time being we mark most of the vars created post-ssagen as
"not a merge candidate".

Stack slot merging for locals/autos is enabled by default if "-N" is
not in effect, and can be disabled via "-gcflags=-d=mergelocals=0".

Fixmes/todos/restrictions:
- try lowering size restrictions
- re-evaluate the various skips that happen in SSA-created autotmps

Updates #62737.
Updates #65532.
Updates #65495.

Change-Id: Ifda26bc48cde5667de245c8a9671b3f0a30bb45d
Reviewed-on: https://go-review.googlesource.com/c/go/+/575415
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
2024-04-09 16:41:23 +00:00

434 lines
6.9 KiB
Go

// errorcheck
//go:build amd64
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Issue 2444
// Issue 4666: issue with arrays of exactly 4GB.
package main
var z [10 << 20]byte
func main() { // GC_ERROR "stack frame too large"
// seq 1 206 | sed 's/.*/ var x& [10<<20]byte/'
// seq 1 206 | sed 's/.*/ z = x&/'
var x1 [10<<20]byte
var x2 [10<<20]byte
var x3 [10<<20]byte
var x4 [10<<20]byte
var x5 [10<<20]byte
var x6 [10<<20]byte
var x7 [10<<20]byte
var x8 [10<<20]byte
var x9 [10<<20]byte
var x10 [10<<20]byte
var x11 [10<<20]byte
var x12 [10<<20]byte
var x13 [10<<20]byte
var x14 [10<<20]byte
var x15 [10<<20]byte
var x16 [10<<20]byte
var x17 [10<<20]byte
var x18 [10<<20]byte
var x19 [10<<20]byte
var x20 [10<<20]byte
var x21 [10<<20]byte
var x22 [10<<20]byte
var x23 [10<<20]byte
var x24 [10<<20]byte
var x25 [10<<20]byte
var x26 [10<<20]byte
var x27 [10<<20]byte
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var x31 [10<<20]byte
var x32 [10<<20]byte
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var x35 [10<<20]byte
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var x38 [10<<20]byte
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var x50 [10<<20]byte
var x51 [10<<20]byte
var x52 [10<<20]byte
var x53 [10<<20]byte
var x54 [10<<20]byte
var x55 [10<<20]byte
var x56 [10<<20]byte
var x57 [10<<20]byte
var x58 [10<<20]byte
var x59 [10<<20]byte
var x60 [10<<20]byte
var x61 [10<<20]byte
var x62 [10<<20]byte
var x63 [10<<20]byte
var x64 [10<<20]byte
var x65 [10<<20]byte
var x66 [10<<20]byte
var x67 [10<<20]byte
var x68 [10<<20]byte
var x69 [10<<20]byte
var x70 [10<<20]byte
var x71 [10<<20]byte
var x72 [10<<20]byte
var x73 [10<<20]byte
var x74 [10<<20]byte
var x75 [10<<20]byte
var x76 [10<<20]byte
var x77 [10<<20]byte
var x78 [10<<20]byte
var x79 [10<<20]byte
var x80 [10<<20]byte
var x81 [10<<20]byte
var x82 [10<<20]byte
var x83 [10<<20]byte
var x84 [10<<20]byte
var x85 [10<<20]byte
var x86 [10<<20]byte
var x87 [10<<20]byte
var x88 [10<<20]byte
var x89 [10<<20]byte
var x90 [10<<20]byte
var x91 [10<<20]byte
var x92 [10<<20]byte
var x93 [10<<20]byte
var x94 [10<<20]byte
var x95 [10<<20]byte
var x96 [10<<20]byte
var x97 [10<<20]byte
var x98 [10<<20]byte
var x99 [10<<20]byte
var x100 [10<<20]byte
var x101 [10<<20]byte
var x102 [10<<20]byte
var x103 [10<<20]byte
var x104 [10<<20]byte
var x105 [10<<20]byte
var x106 [10<<20]byte
var x107 [10<<20]byte
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var x109 [10<<20]byte
var x110 [10<<20]byte
var x111 [10<<20]byte
var x112 [10<<20]byte
var x113 [10<<20]byte
var x114 [10<<20]byte
var x115 [10<<20]byte
var x116 [10<<20]byte
var x117 [10<<20]byte
var x118 [10<<20]byte
var x119 [10<<20]byte
var x120 [10<<20]byte
var x121 [10<<20]byte
var x122 [10<<20]byte
var x123 [10<<20]byte
var x124 [10<<20]byte
var x125 [10<<20]byte
var x126 [10<<20]byte
var x127 [10<<20]byte
var x128 [10<<20]byte
var x129 [10<<20]byte
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var x131 [10<<20]byte
var x132 [10<<20]byte
var x133 [10<<20]byte
var x134 [10<<20]byte
var x135 [10<<20]byte
var x136 [10<<20]byte
var x137 [10<<20]byte
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var x139 [10<<20]byte
var x140 [10<<20]byte
var x141 [10<<20]byte
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var x144 [10<<20]byte
var x145 [10<<20]byte
var x146 [10<<20]byte
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var x150 [10<<20]byte
var x151 [10<<20]byte
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var x154 [10<<20]byte
var x155 [10<<20]byte
var x156 [10<<20]byte
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var x160 [10<<20]byte
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var x165 [10<<20]byte
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var x168 [10<<20]byte
var x169 [10<<20]byte
var x170 [10<<20]byte
var x171 [10<<20]byte
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var x203 [10<<20]byte
var x204 [10<<20]byte
var x205 [10<<20]byte
var x206 [10<<20]byte
var x207 [10<<20]byte
z = x1
z = x2
z = x3
z = x4
z = x5
z = x6
z = x7
z = x8
z = x9
z = x10
z = x11
z = x12
z = x13
z = x14
z = x15
z = x16
z = x17
z = x18
z = x19
z = x20
z = x21
z = x22
z = x23
z = x24
z = x25
z = x26
z = x27
z = x28
z = x29
z = x30
z = x31
z = x32
z = x33
z = x34
z = x35
z = x36
z = x37
z = x38
z = x39
z = x40
z = x41
z = x42
z = x43
z = x44
z = x45
z = x46
z = x47
z = x48
z = x49
z = x50
z = x51
z = x52
z = x53
z = x54
z = x55
z = x56
z = x57
z = x58
z = x59
z = x60
z = x61
z = x62
z = x63
z = x64
z = x65
z = x66
z = x67
z = x68
z = x69
z = x70
z = x71
z = x72
z = x73
z = x74
z = x75
z = x76
z = x77
z = x78
z = x79
z = x80
z = x81
z = x82
z = x83
z = x84
z = x85
z = x86
z = x87
z = x88
z = x89
z = x90
z = x91
z = x92
z = x93
z = x94
z = x95
z = x96
z = x97
z = x98
z = x99
z = x100
z = x101
z = x102
z = x103
z = x104
z = x105
z = x106
z = x107
z = x108
z = x109
z = x110
z = x111
z = x112
z = x113
z = x114
z = x115
z = x116
z = x117
z = x118
z = x119
z = x120
z = x121
z = x122
z = x123
z = x124
z = x125
z = x126
z = x127
z = x128
z = x129
z = x130
z = x131
z = x132
z = x133
z = x134
z = x135
z = x136
z = x137
z = x138
z = x139
z = x140
z = x141
z = x142
z = x143
z = x144
z = x145
z = x146
z = x147
z = x148
z = x149
z = x150
z = x151
z = x152
z = x153
z = x154
z = x155
z = x156
z = x157
z = x158
z = x159
z = x160
z = x161
z = x162
z = x163
z = x164
z = x165
z = x166
z = x167
z = x168
z = x169
z = x170
z = x171
z = x172
z = x173
z = x174
z = x175
z = x176
z = x177
z = x178
z = x179
z = x180
z = x181
z = x182
z = x183
z = x184
z = x185
z = x186
z = x187
z = x188
z = x189
z = x190
z = x191
z = x192
z = x193
z = x194
z = x195
z = x196
z = x197
z = x198
z = x199
z = x200
z = x201
z = x202
z = x203
z = x204
z = x205
z = x206
z = x207
}