2016-12-15 15:13:50 +08:00
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# RUN: llc -mtriple=x86_64-apple-macosx10.12.0 -O3 -run-pass=block-placement -o - %s | FileCheck %s
|
[MachineBlockPlacement] Don't make blocks "uneditable"
Summary:
This fixes an issue with MachineBlockPlacement due to a badly timed call
to `analyzeBranch` with `AllowModify` set to true. The timeline is as
follows:
1. `MachineBlockPlacement::maybeTailDuplicateBlock` calls
`TailDup.shouldTailDuplicate` on its argument, which in turn calls
`analyzeBranch` with `AllowModify` set to true.
2. This `analyzeBranch` call edits the terminator sequence of the block
based on the physical layout of the machine function, turning an
unanalyzable non-fallthrough block to a unanalyzable fallthrough
block. Normally MBP bails out of rearranging such blocks, but this
block was unanalyzable non-fallthrough (and thus rearrangeable) the
first time MBP looked at it, and so it goes ahead and decides where
it should be placed in the function.
3. When placing this block MBP fails to analyze and thus update the
block in keeping with the new physical layout.
Concretely, before (1) we have something like:
```
LBL0:
< unknown terminator op that may branch to LBL1 >
jmp LBL1
LBL1:
... A
LBL2:
... B
```
In (2), analyze branch simplifies this to
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump removed
LBL1:
... A
LBL2:
... B
```
In (3), MachineBlockPlacement goes ahead with its plan of putting LBL2
after the first block since that is profitable.
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump
LBL2:
... B
LBL1:
... A
```
and the program now has incorrect behavior (we no longer fall-through
from `LBL0` to `LBL1`) because MBP can no longer edit LBL0.
There are several possible solutions, but I went with removing the teeth
off of the `analyzeBranch` calls in TailDuplicator. That makes thinking
about the result of these calls easier, and breaks nothing in the lit
test suite.
I've also added some bookkeeping to the MachineBlockPlacement pass and
used that to write an assert that would have caught this.
Reviewers: chandlerc, gberry, MatzeB, iteratee
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D27783
llvm-svn: 289764
2016-12-15 13:08:57 +08:00
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--- |
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; ModuleID = 'test.ll'
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source_filename = "test.ll"
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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declare void @stub(i32*)
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define i32 @f(i32* %ptr, i1 %cond) {
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entry:
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br i1 %cond, label %left, label %right
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left: ; preds = %entry
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%is_null = icmp eq i32* %ptr, null
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br i1 %is_null, label %null, label %not_null, !prof !0, !make.implicit !1
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not_null: ; preds = %left
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%val = load i32, i32* %ptr
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ret i32 %val
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null: ; preds = %left
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call void @stub(i32* %ptr)
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unreachable
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right: ; preds = %entry
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call void @stub(i32* null)
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unreachable
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}
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; Function Attrs: nounwind
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declare void @llvm.stackprotector(i8*, i8**) #0
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attributes #0 = { nounwind }
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!0 = !{!"branch_weights", i32 1048575, i32 1}
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!1 = !{}
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...
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---
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# CHECK: name: f
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name: f
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alignment: 4
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tracksRegLiveness: true
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liveins:
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2018-02-01 06:04:26 +08:00
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- { reg: '$rdi' }
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- { reg: '$esi' }
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[MachineBlockPlacement] Don't make blocks "uneditable"
Summary:
This fixes an issue with MachineBlockPlacement due to a badly timed call
to `analyzeBranch` with `AllowModify` set to true. The timeline is as
follows:
1. `MachineBlockPlacement::maybeTailDuplicateBlock` calls
`TailDup.shouldTailDuplicate` on its argument, which in turn calls
`analyzeBranch` with `AllowModify` set to true.
2. This `analyzeBranch` call edits the terminator sequence of the block
based on the physical layout of the machine function, turning an
unanalyzable non-fallthrough block to a unanalyzable fallthrough
block. Normally MBP bails out of rearranging such blocks, but this
block was unanalyzable non-fallthrough (and thus rearrangeable) the
first time MBP looked at it, and so it goes ahead and decides where
it should be placed in the function.
3. When placing this block MBP fails to analyze and thus update the
block in keeping with the new physical layout.
Concretely, before (1) we have something like:
```
LBL0:
< unknown terminator op that may branch to LBL1 >
jmp LBL1
LBL1:
... A
LBL2:
... B
```
In (2), analyze branch simplifies this to
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump removed
LBL1:
... A
LBL2:
... B
```
In (3), MachineBlockPlacement goes ahead with its plan of putting LBL2
after the first block since that is profitable.
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump
LBL2:
... B
LBL1:
... A
```
and the program now has incorrect behavior (we no longer fall-through
from `LBL0` to `LBL1`) because MBP can no longer edit LBL0.
There are several possible solutions, but I went with removing the teeth
off of the `analyzeBranch` calls in TailDuplicator. That makes thinking
about the result of these calls easier, and breaks nothing in the lit
test suite.
I've also added some bookkeeping to the MachineBlockPlacement pass and
used that to write an assert that would have caught this.
Reviewers: chandlerc, gberry, MatzeB, iteratee
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D27783
llvm-svn: 289764
2016-12-15 13:08:57 +08:00
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2018-02-01 06:04:26 +08:00
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# CHECK: $eax = FAULTING_OP 1, %bb.3, 1684, killed $rdi, 1, $noreg, 0, $noreg :: (load 4 from %ir.ptr)
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2017-12-05 01:18:51 +08:00
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# CHECK-NEXT: JMP_1 %bb.2
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[MachineBlockPlacement] Don't make blocks "uneditable"
Summary:
This fixes an issue with MachineBlockPlacement due to a badly timed call
to `analyzeBranch` with `AllowModify` set to true. The timeline is as
follows:
1. `MachineBlockPlacement::maybeTailDuplicateBlock` calls
`TailDup.shouldTailDuplicate` on its argument, which in turn calls
`analyzeBranch` with `AllowModify` set to true.
2. This `analyzeBranch` call edits the terminator sequence of the block
based on the physical layout of the machine function, turning an
unanalyzable non-fallthrough block to a unanalyzable fallthrough
block. Normally MBP bails out of rearranging such blocks, but this
block was unanalyzable non-fallthrough (and thus rearrangeable) the
first time MBP looked at it, and so it goes ahead and decides where
it should be placed in the function.
3. When placing this block MBP fails to analyze and thus update the
block in keeping with the new physical layout.
Concretely, before (1) we have something like:
```
LBL0:
< unknown terminator op that may branch to LBL1 >
jmp LBL1
LBL1:
... A
LBL2:
... B
```
In (2), analyze branch simplifies this to
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump removed
LBL1:
... A
LBL2:
... B
```
In (3), MachineBlockPlacement goes ahead with its plan of putting LBL2
after the first block since that is profitable.
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump
LBL2:
... B
LBL1:
... A
```
and the program now has incorrect behavior (we no longer fall-through
from `LBL0` to `LBL1`) because MBP can no longer edit LBL0.
There are several possible solutions, but I went with removing the teeth
off of the `analyzeBranch` calls in TailDuplicator. That makes thinking
about the result of these calls easier, and breaks nothing in the lit
test suite.
I've also added some bookkeeping to the MachineBlockPlacement pass and
used that to write an assert that would have caught this.
Reviewers: chandlerc, gberry, MatzeB, iteratee
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D27783
llvm-svn: 289764
2016-12-15 13:08:57 +08:00
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# CHECK: bb.3.null:
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# CHECK: bb.4.right:
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# CHECK: bb.2.not_null:
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body: |
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bb.0.entry:
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2017-12-05 01:18:51 +08:00
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successors: %bb.1(0x7ffff800), %bb.3(0x00000800)
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2018-02-01 06:04:26 +08:00
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liveins: $esi, $rdi
|
[MachineBlockPlacement] Don't make blocks "uneditable"
Summary:
This fixes an issue with MachineBlockPlacement due to a badly timed call
to `analyzeBranch` with `AllowModify` set to true. The timeline is as
follows:
1. `MachineBlockPlacement::maybeTailDuplicateBlock` calls
`TailDup.shouldTailDuplicate` on its argument, which in turn calls
`analyzeBranch` with `AllowModify` set to true.
2. This `analyzeBranch` call edits the terminator sequence of the block
based on the physical layout of the machine function, turning an
unanalyzable non-fallthrough block to a unanalyzable fallthrough
block. Normally MBP bails out of rearranging such blocks, but this
block was unanalyzable non-fallthrough (and thus rearrangeable) the
first time MBP looked at it, and so it goes ahead and decides where
it should be placed in the function.
3. When placing this block MBP fails to analyze and thus update the
block in keeping with the new physical layout.
Concretely, before (1) we have something like:
```
LBL0:
< unknown terminator op that may branch to LBL1 >
jmp LBL1
LBL1:
... A
LBL2:
... B
```
In (2), analyze branch simplifies this to
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump removed
LBL1:
... A
LBL2:
... B
```
In (3), MachineBlockPlacement goes ahead with its plan of putting LBL2
after the first block since that is profitable.
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump
LBL2:
... B
LBL1:
... A
```
and the program now has incorrect behavior (we no longer fall-through
from `LBL0` to `LBL1`) because MBP can no longer edit LBL0.
There are several possible solutions, but I went with removing the teeth
off of the `analyzeBranch` calls in TailDuplicator. That makes thinking
about the result of these calls easier, and breaks nothing in the lit
test suite.
I've also added some bookkeeping to the MachineBlockPlacement pass and
used that to write an assert that would have caught this.
Reviewers: chandlerc, gberry, MatzeB, iteratee
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D27783
llvm-svn: 289764
2016-12-15 13:08:57 +08:00
|
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2018-02-01 06:04:26 +08:00
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frame-setup PUSH64r undef $rax, implicit-def $rsp, implicit $rsp
|
[MachineBlockPlacement] Don't make blocks "uneditable"
Summary:
This fixes an issue with MachineBlockPlacement due to a badly timed call
to `analyzeBranch` with `AllowModify` set to true. The timeline is as
follows:
1. `MachineBlockPlacement::maybeTailDuplicateBlock` calls
`TailDup.shouldTailDuplicate` on its argument, which in turn calls
`analyzeBranch` with `AllowModify` set to true.
2. This `analyzeBranch` call edits the terminator sequence of the block
based on the physical layout of the machine function, turning an
unanalyzable non-fallthrough block to a unanalyzable fallthrough
block. Normally MBP bails out of rearranging such blocks, but this
block was unanalyzable non-fallthrough (and thus rearrangeable) the
first time MBP looked at it, and so it goes ahead and decides where
it should be placed in the function.
3. When placing this block MBP fails to analyze and thus update the
block in keeping with the new physical layout.
Concretely, before (1) we have something like:
```
LBL0:
< unknown terminator op that may branch to LBL1 >
jmp LBL1
LBL1:
... A
LBL2:
... B
```
In (2), analyze branch simplifies this to
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump removed
LBL1:
... A
LBL2:
... B
```
In (3), MachineBlockPlacement goes ahead with its plan of putting LBL2
after the first block since that is profitable.
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump
LBL2:
... B
LBL1:
... A
```
and the program now has incorrect behavior (we no longer fall-through
from `LBL0` to `LBL1`) because MBP can no longer edit LBL0.
There are several possible solutions, but I went with removing the teeth
off of the `analyzeBranch` calls in TailDuplicator. That makes thinking
about the result of these calls easier, and breaks nothing in the lit
test suite.
I've also added some bookkeeping to the MachineBlockPlacement pass and
used that to write an assert that would have caught this.
Reviewers: chandlerc, gberry, MatzeB, iteratee
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D27783
llvm-svn: 289764
2016-12-15 13:08:57 +08:00
|
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CFI_INSTRUCTION def_cfa_offset 16
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2018-02-01 06:04:26 +08:00
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TEST8ri $sil, 1, implicit-def $eflags, implicit killed $esi
|
[X86] Merge the different Jcc instructions for each condition code into single instructions that store the condition code as an operand.
Summary:
This avoids needing an isel pattern for each condition code. And it removes translation switches for converting between Jcc instructions and condition codes.
Now the printer, encoder and disassembler take care of converting the immediate. We use InstAliases to handle the assembly matching. But we print using the asm string in the instruction definition. The instruction itself is marked IsCodeGenOnly=1 to hide it from the assembly parser.
Reviewers: spatel, lebedev.ri, courbet, gchatelet, RKSimon
Reviewed By: RKSimon
Subscribers: MatzeB, qcolombet, eraman, hiraditya, arphaman, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60228
llvm-svn: 357802
2019-04-06 03:28:09 +08:00
|
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|
JCC_1 %bb.3, 4, implicit killed $eflags
|
[MachineBlockPlacement] Don't make blocks "uneditable"
Summary:
This fixes an issue with MachineBlockPlacement due to a badly timed call
to `analyzeBranch` with `AllowModify` set to true. The timeline is as
follows:
1. `MachineBlockPlacement::maybeTailDuplicateBlock` calls
`TailDup.shouldTailDuplicate` on its argument, which in turn calls
`analyzeBranch` with `AllowModify` set to true.
2. This `analyzeBranch` call edits the terminator sequence of the block
based on the physical layout of the machine function, turning an
unanalyzable non-fallthrough block to a unanalyzable fallthrough
block. Normally MBP bails out of rearranging such blocks, but this
block was unanalyzable non-fallthrough (and thus rearrangeable) the
first time MBP looked at it, and so it goes ahead and decides where
it should be placed in the function.
3. When placing this block MBP fails to analyze and thus update the
block in keeping with the new physical layout.
Concretely, before (1) we have something like:
```
LBL0:
< unknown terminator op that may branch to LBL1 >
jmp LBL1
LBL1:
... A
LBL2:
... B
```
In (2), analyze branch simplifies this to
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump removed
LBL1:
... A
LBL2:
... B
```
In (3), MachineBlockPlacement goes ahead with its plan of putting LBL2
after the first block since that is profitable.
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump
LBL2:
... B
LBL1:
... A
```
and the program now has incorrect behavior (we no longer fall-through
from `LBL0` to `LBL1`) because MBP can no longer edit LBL0.
There are several possible solutions, but I went with removing the teeth
off of the `analyzeBranch` calls in TailDuplicator. That makes thinking
about the result of these calls easier, and breaks nothing in the lit
test suite.
I've also added some bookkeeping to the MachineBlockPlacement pass and
used that to write an assert that would have caught this.
Reviewers: chandlerc, gberry, MatzeB, iteratee
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D27783
llvm-svn: 289764
2016-12-15 13:08:57 +08:00
|
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|
|
|
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|
bb.1.left:
|
2017-12-05 01:18:51 +08:00
|
|
|
successors: %bb.2(0x7ffff800), %bb.4(0x00000800)
|
2018-02-01 06:04:26 +08:00
|
|
|
liveins: $rdi
|
[MachineBlockPlacement] Don't make blocks "uneditable"
Summary:
This fixes an issue with MachineBlockPlacement due to a badly timed call
to `analyzeBranch` with `AllowModify` set to true. The timeline is as
follows:
1. `MachineBlockPlacement::maybeTailDuplicateBlock` calls
`TailDup.shouldTailDuplicate` on its argument, which in turn calls
`analyzeBranch` with `AllowModify` set to true.
2. This `analyzeBranch` call edits the terminator sequence of the block
based on the physical layout of the machine function, turning an
unanalyzable non-fallthrough block to a unanalyzable fallthrough
block. Normally MBP bails out of rearranging such blocks, but this
block was unanalyzable non-fallthrough (and thus rearrangeable) the
first time MBP looked at it, and so it goes ahead and decides where
it should be placed in the function.
3. When placing this block MBP fails to analyze and thus update the
block in keeping with the new physical layout.
Concretely, before (1) we have something like:
```
LBL0:
< unknown terminator op that may branch to LBL1 >
jmp LBL1
LBL1:
... A
LBL2:
... B
```
In (2), analyze branch simplifies this to
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump removed
LBL1:
... A
LBL2:
... B
```
In (3), MachineBlockPlacement goes ahead with its plan of putting LBL2
after the first block since that is profitable.
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump
LBL2:
... B
LBL1:
... A
```
and the program now has incorrect behavior (we no longer fall-through
from `LBL0` to `LBL1`) because MBP can no longer edit LBL0.
There are several possible solutions, but I went with removing the teeth
off of the `analyzeBranch` calls in TailDuplicator. That makes thinking
about the result of these calls easier, and breaks nothing in the lit
test suite.
I've also added some bookkeeping to the MachineBlockPlacement pass and
used that to write an assert that would have caught this.
Reviewers: chandlerc, gberry, MatzeB, iteratee
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D27783
llvm-svn: 289764
2016-12-15 13:08:57 +08:00
|
|
|
|
2018-02-01 06:04:26 +08:00
|
|
|
$eax = FAULTING_OP 1, %bb.2, 1684, killed $rdi, 1, $noreg, 0, $noreg :: (load 4 from %ir.ptr)
|
2017-12-05 01:18:51 +08:00
|
|
|
JMP_1 %bb.4
|
[MachineBlockPlacement] Don't make blocks "uneditable"
Summary:
This fixes an issue with MachineBlockPlacement due to a badly timed call
to `analyzeBranch` with `AllowModify` set to true. The timeline is as
follows:
1. `MachineBlockPlacement::maybeTailDuplicateBlock` calls
`TailDup.shouldTailDuplicate` on its argument, which in turn calls
`analyzeBranch` with `AllowModify` set to true.
2. This `analyzeBranch` call edits the terminator sequence of the block
based on the physical layout of the machine function, turning an
unanalyzable non-fallthrough block to a unanalyzable fallthrough
block. Normally MBP bails out of rearranging such blocks, but this
block was unanalyzable non-fallthrough (and thus rearrangeable) the
first time MBP looked at it, and so it goes ahead and decides where
it should be placed in the function.
3. When placing this block MBP fails to analyze and thus update the
block in keeping with the new physical layout.
Concretely, before (1) we have something like:
```
LBL0:
< unknown terminator op that may branch to LBL1 >
jmp LBL1
LBL1:
... A
LBL2:
... B
```
In (2), analyze branch simplifies this to
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump removed
LBL1:
... A
LBL2:
... B
```
In (3), MachineBlockPlacement goes ahead with its plan of putting LBL2
after the first block since that is profitable.
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump
LBL2:
... B
LBL1:
... A
```
and the program now has incorrect behavior (we no longer fall-through
from `LBL0` to `LBL1`) because MBP can no longer edit LBL0.
There are several possible solutions, but I went with removing the teeth
off of the `analyzeBranch` calls in TailDuplicator. That makes thinking
about the result of these calls easier, and breaks nothing in the lit
test suite.
I've also added some bookkeeping to the MachineBlockPlacement pass and
used that to write an assert that would have caught this.
Reviewers: chandlerc, gberry, MatzeB, iteratee
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D27783
llvm-svn: 289764
2016-12-15 13:08:57 +08:00
|
|
|
|
|
|
|
|
bb.4.not_null:
|
2018-02-01 06:04:26 +08:00
|
|
|
liveins: $rdi, $eax
|
[MachineBlockPlacement] Don't make blocks "uneditable"
Summary:
This fixes an issue with MachineBlockPlacement due to a badly timed call
to `analyzeBranch` with `AllowModify` set to true. The timeline is as
follows:
1. `MachineBlockPlacement::maybeTailDuplicateBlock` calls
`TailDup.shouldTailDuplicate` on its argument, which in turn calls
`analyzeBranch` with `AllowModify` set to true.
2. This `analyzeBranch` call edits the terminator sequence of the block
based on the physical layout of the machine function, turning an
unanalyzable non-fallthrough block to a unanalyzable fallthrough
block. Normally MBP bails out of rearranging such blocks, but this
block was unanalyzable non-fallthrough (and thus rearrangeable) the
first time MBP looked at it, and so it goes ahead and decides where
it should be placed in the function.
3. When placing this block MBP fails to analyze and thus update the
block in keeping with the new physical layout.
Concretely, before (1) we have something like:
```
LBL0:
< unknown terminator op that may branch to LBL1 >
jmp LBL1
LBL1:
... A
LBL2:
... B
```
In (2), analyze branch simplifies this to
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump removed
LBL1:
... A
LBL2:
... B
```
In (3), MachineBlockPlacement goes ahead with its plan of putting LBL2
after the first block since that is profitable.
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump
LBL2:
... B
LBL1:
... A
```
and the program now has incorrect behavior (we no longer fall-through
from `LBL0` to `LBL1`) because MBP can no longer edit LBL0.
There are several possible solutions, but I went with removing the teeth
off of the `analyzeBranch` calls in TailDuplicator. That makes thinking
about the result of these calls easier, and breaks nothing in the lit
test suite.
I've also added some bookkeeping to the MachineBlockPlacement pass and
used that to write an assert that would have caught this.
Reviewers: chandlerc, gberry, MatzeB, iteratee
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D27783
llvm-svn: 289764
2016-12-15 13:08:57 +08:00
|
|
|
|
2018-02-01 06:04:26 +08:00
|
|
|
$rcx = POP64r implicit-def $rsp, implicit $rsp
|
|
|
|
|
RETQ $eax
|
[MachineBlockPlacement] Don't make blocks "uneditable"
Summary:
This fixes an issue with MachineBlockPlacement due to a badly timed call
to `analyzeBranch` with `AllowModify` set to true. The timeline is as
follows:
1. `MachineBlockPlacement::maybeTailDuplicateBlock` calls
`TailDup.shouldTailDuplicate` on its argument, which in turn calls
`analyzeBranch` with `AllowModify` set to true.
2. This `analyzeBranch` call edits the terminator sequence of the block
based on the physical layout of the machine function, turning an
unanalyzable non-fallthrough block to a unanalyzable fallthrough
block. Normally MBP bails out of rearranging such blocks, but this
block was unanalyzable non-fallthrough (and thus rearrangeable) the
first time MBP looked at it, and so it goes ahead and decides where
it should be placed in the function.
3. When placing this block MBP fails to analyze and thus update the
block in keeping with the new physical layout.
Concretely, before (1) we have something like:
```
LBL0:
< unknown terminator op that may branch to LBL1 >
jmp LBL1
LBL1:
... A
LBL2:
... B
```
In (2), analyze branch simplifies this to
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump removed
LBL1:
... A
LBL2:
... B
```
In (3), MachineBlockPlacement goes ahead with its plan of putting LBL2
after the first block since that is profitable.
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump
LBL2:
... B
LBL1:
... A
```
and the program now has incorrect behavior (we no longer fall-through
from `LBL0` to `LBL1`) because MBP can no longer edit LBL0.
There are several possible solutions, but I went with removing the teeth
off of the `analyzeBranch` calls in TailDuplicator. That makes thinking
about the result of these calls easier, and breaks nothing in the lit
test suite.
I've also added some bookkeeping to the MachineBlockPlacement pass and
used that to write an assert that would have caught this.
Reviewers: chandlerc, gberry, MatzeB, iteratee
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D27783
llvm-svn: 289764
2016-12-15 13:08:57 +08:00
|
|
|
|
|
|
|
|
bb.2.null:
|
2018-02-01 06:04:26 +08:00
|
|
|
liveins: $rdi
|
[MachineBlockPlacement] Don't make blocks "uneditable"
Summary:
This fixes an issue with MachineBlockPlacement due to a badly timed call
to `analyzeBranch` with `AllowModify` set to true. The timeline is as
follows:
1. `MachineBlockPlacement::maybeTailDuplicateBlock` calls
`TailDup.shouldTailDuplicate` on its argument, which in turn calls
`analyzeBranch` with `AllowModify` set to true.
2. This `analyzeBranch` call edits the terminator sequence of the block
based on the physical layout of the machine function, turning an
unanalyzable non-fallthrough block to a unanalyzable fallthrough
block. Normally MBP bails out of rearranging such blocks, but this
block was unanalyzable non-fallthrough (and thus rearrangeable) the
first time MBP looked at it, and so it goes ahead and decides where
it should be placed in the function.
3. When placing this block MBP fails to analyze and thus update the
block in keeping with the new physical layout.
Concretely, before (1) we have something like:
```
LBL0:
< unknown terminator op that may branch to LBL1 >
jmp LBL1
LBL1:
... A
LBL2:
... B
```
In (2), analyze branch simplifies this to
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump removed
LBL1:
... A
LBL2:
... B
```
In (3), MachineBlockPlacement goes ahead with its plan of putting LBL2
after the first block since that is profitable.
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump
LBL2:
... B
LBL1:
... A
```
and the program now has incorrect behavior (we no longer fall-through
from `LBL0` to `LBL1`) because MBP can no longer edit LBL0.
There are several possible solutions, but I went with removing the teeth
off of the `analyzeBranch` calls in TailDuplicator. That makes thinking
about the result of these calls easier, and breaks nothing in the lit
test suite.
I've also added some bookkeeping to the MachineBlockPlacement pass and
used that to write an assert that would have caught this.
Reviewers: chandlerc, gberry, MatzeB, iteratee
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D27783
llvm-svn: 289764
2016-12-15 13:08:57 +08:00
|
|
|
|
2018-02-01 06:04:26 +08:00
|
|
|
CALL64pcrel32 @stub, csr_64, implicit $rsp, implicit $rdi, implicit-def $rsp
|
[MachineBlockPlacement] Don't make blocks "uneditable"
Summary:
This fixes an issue with MachineBlockPlacement due to a badly timed call
to `analyzeBranch` with `AllowModify` set to true. The timeline is as
follows:
1. `MachineBlockPlacement::maybeTailDuplicateBlock` calls
`TailDup.shouldTailDuplicate` on its argument, which in turn calls
`analyzeBranch` with `AllowModify` set to true.
2. This `analyzeBranch` call edits the terminator sequence of the block
based on the physical layout of the machine function, turning an
unanalyzable non-fallthrough block to a unanalyzable fallthrough
block. Normally MBP bails out of rearranging such blocks, but this
block was unanalyzable non-fallthrough (and thus rearrangeable) the
first time MBP looked at it, and so it goes ahead and decides where
it should be placed in the function.
3. When placing this block MBP fails to analyze and thus update the
block in keeping with the new physical layout.
Concretely, before (1) we have something like:
```
LBL0:
< unknown terminator op that may branch to LBL1 >
jmp LBL1
LBL1:
... A
LBL2:
... B
```
In (2), analyze branch simplifies this to
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump removed
LBL1:
... A
LBL2:
... B
```
In (3), MachineBlockPlacement goes ahead with its plan of putting LBL2
after the first block since that is profitable.
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump
LBL2:
... B
LBL1:
... A
```
and the program now has incorrect behavior (we no longer fall-through
from `LBL0` to `LBL1`) because MBP can no longer edit LBL0.
There are several possible solutions, but I went with removing the teeth
off of the `analyzeBranch` calls in TailDuplicator. That makes thinking
about the result of these calls easier, and breaks nothing in the lit
test suite.
I've also added some bookkeeping to the MachineBlockPlacement pass and
used that to write an assert that would have caught this.
Reviewers: chandlerc, gberry, MatzeB, iteratee
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D27783
llvm-svn: 289764
2016-12-15 13:08:57 +08:00
|
|
|
|
|
|
|
|
bb.3.right:
|
2018-02-01 06:04:26 +08:00
|
|
|
dead $edi = XOR32rr undef $edi, undef $edi, implicit-def dead $eflags, implicit-def $rdi
|
|
|
|
|
CALL64pcrel32 @stub, csr_64, implicit $rsp, implicit $rdi, implicit-def $rsp
|
[MachineBlockPlacement] Don't make blocks "uneditable"
Summary:
This fixes an issue with MachineBlockPlacement due to a badly timed call
to `analyzeBranch` with `AllowModify` set to true. The timeline is as
follows:
1. `MachineBlockPlacement::maybeTailDuplicateBlock` calls
`TailDup.shouldTailDuplicate` on its argument, which in turn calls
`analyzeBranch` with `AllowModify` set to true.
2. This `analyzeBranch` call edits the terminator sequence of the block
based on the physical layout of the machine function, turning an
unanalyzable non-fallthrough block to a unanalyzable fallthrough
block. Normally MBP bails out of rearranging such blocks, but this
block was unanalyzable non-fallthrough (and thus rearrangeable) the
first time MBP looked at it, and so it goes ahead and decides where
it should be placed in the function.
3. When placing this block MBP fails to analyze and thus update the
block in keeping with the new physical layout.
Concretely, before (1) we have something like:
```
LBL0:
< unknown terminator op that may branch to LBL1 >
jmp LBL1
LBL1:
... A
LBL2:
... B
```
In (2), analyze branch simplifies this to
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump removed
LBL1:
... A
LBL2:
... B
```
In (3), MachineBlockPlacement goes ahead with its plan of putting LBL2
after the first block since that is profitable.
```
LBL0:
< unknown terminator op that may branch to LBL2 >
;; jmp LBL1 <- redundant jump
LBL2:
... B
LBL1:
... A
```
and the program now has incorrect behavior (we no longer fall-through
from `LBL0` to `LBL1`) because MBP can no longer edit LBL0.
There are several possible solutions, but I went with removing the teeth
off of the `analyzeBranch` calls in TailDuplicator. That makes thinking
about the result of these calls easier, and breaks nothing in the lit
test suite.
I've also added some bookkeeping to the MachineBlockPlacement pass and
used that to write an assert that would have caught this.
Reviewers: chandlerc, gberry, MatzeB, iteratee
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D27783
llvm-svn: 289764
2016-12-15 13:08:57 +08:00
|
|
|
|
|
|
|
|
...
|