Elide argument copies during instruction selection
Summary:
Avoids tons of prologue boilerplate when arguments are passed in memory
and left in memory. This can happen in a debug build or in a release
build when an argument alloca is escaped. This will dramatically affect
the code size of x86 debug builds, because X86 fast isel doesn't handle
arguments passed in memory at all. It only handles the x86_64 case of up
to 6 basic register parameters.
This is implemented by analyzing the entry block before ISel to identify
copy elision candidates. A copy elision candidate is an argument that is
used to fully initialize an alloca before any other possibly escaping
uses of that alloca. If an argument is a copy elision candidate, we set
a flag on the InputArg. If the the target generates loads from a fixed
stack object that matches the size and alignment requirements of the
alloca, the SelectionDAG builder will delete the stack object created
for the alloca and replace it with the fixed stack object. The load is
left behind to satisfy any remaining uses of the argument value. The
store is now dead and is therefore elided. The fixed stack object is
also marked as mutable, as it may now be modified by the user, and it
would be invalid to rematerialize the initial load from it.
Supersedes D28388
Fixes PR26328
Reviewers: chandlerc, MatzeB, qcolombet, inglorion, hans
Subscribers: igorb, llvm-commits
Differential Revision: https://reviews.llvm.org/D29668
llvm-svn: 296683
2017-03-02 05:42:00 +08:00
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; RUN: llc -mtriple=i686-windows < %s | FileCheck %s
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2017-03-04 09:40:40 +08:00
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declare void @addrof_i1(i1*)
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Elide argument copies during instruction selection
Summary:
Avoids tons of prologue boilerplate when arguments are passed in memory
and left in memory. This can happen in a debug build or in a release
build when an argument alloca is escaped. This will dramatically affect
the code size of x86 debug builds, because X86 fast isel doesn't handle
arguments passed in memory at all. It only handles the x86_64 case of up
to 6 basic register parameters.
This is implemented by analyzing the entry block before ISel to identify
copy elision candidates. A copy elision candidate is an argument that is
used to fully initialize an alloca before any other possibly escaping
uses of that alloca. If an argument is a copy elision candidate, we set
a flag on the InputArg. If the the target generates loads from a fixed
stack object that matches the size and alignment requirements of the
alloca, the SelectionDAG builder will delete the stack object created
for the alloca and replace it with the fixed stack object. The load is
left behind to satisfy any remaining uses of the argument value. The
store is now dead and is therefore elided. The fixed stack object is
also marked as mutable, as it may now be modified by the user, and it
would be invalid to rematerialize the initial load from it.
Supersedes D28388
Fixes PR26328
Reviewers: chandlerc, MatzeB, qcolombet, inglorion, hans
Subscribers: igorb, llvm-commits
Differential Revision: https://reviews.llvm.org/D29668
llvm-svn: 296683
2017-03-02 05:42:00 +08:00
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declare void @addrof_i32(i32*)
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declare void @addrof_i64(i64*)
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declare void @addrof_i128(i128*)
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declare void @addrof_i32_x3(i32*, i32*, i32*)
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define void @simple(i32 %x) {
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entry:
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%x.addr = alloca i32
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store i32 %x, i32* %x.addr
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call void @addrof_i32(i32* %x.addr)
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ret void
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}
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; CHECK-LABEL: _simple:
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; CHECK: leal 4(%esp), %[[reg:[^ ]*]]
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; CHECK: pushl %[[reg]]
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; CHECK: calll _addrof_i32
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; CHECK: retl
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; We need to load %x before calling addrof_i32 now because it could mutate %x in
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; place.
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define i32 @use_arg(i32 %x) {
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entry:
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%x.addr = alloca i32
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store i32 %x, i32* %x.addr
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call void @addrof_i32(i32* %x.addr)
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ret i32 %x
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}
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; CHECK-LABEL: _use_arg:
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; CHECK: pushl %[[csr:[^ ]*]]
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; CHECK-DAG: movl 8(%esp), %[[csr]]
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; CHECK-DAG: leal 8(%esp), %[[reg:[^ ]*]]
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; CHECK: pushl %[[reg]]
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; CHECK: calll _addrof_i32
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; CHECK: movl %[[csr]], %eax
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; CHECK: popl %[[csr]]
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; CHECK: retl
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2017-03-04 09:40:40 +08:00
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; We won't copy elide for types needing legalization such as i64 or i1.
|
Elide argument copies during instruction selection
Summary:
Avoids tons of prologue boilerplate when arguments are passed in memory
and left in memory. This can happen in a debug build or in a release
build when an argument alloca is escaped. This will dramatically affect
the code size of x86 debug builds, because X86 fast isel doesn't handle
arguments passed in memory at all. It only handles the x86_64 case of up
to 6 basic register parameters.
This is implemented by analyzing the entry block before ISel to identify
copy elision candidates. A copy elision candidate is an argument that is
used to fully initialize an alloca before any other possibly escaping
uses of that alloca. If an argument is a copy elision candidate, we set
a flag on the InputArg. If the the target generates loads from a fixed
stack object that matches the size and alignment requirements of the
alloca, the SelectionDAG builder will delete the stack object created
for the alloca and replace it with the fixed stack object. The load is
left behind to satisfy any remaining uses of the argument value. The
store is now dead and is therefore elided. The fixed stack object is
also marked as mutable, as it may now be modified by the user, and it
would be invalid to rematerialize the initial load from it.
Supersedes D28388
Fixes PR26328
Reviewers: chandlerc, MatzeB, qcolombet, inglorion, hans
Subscribers: igorb, llvm-commits
Differential Revision: https://reviews.llvm.org/D29668
llvm-svn: 296683
2017-03-02 05:42:00 +08:00
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define i64 @split_i64(i64 %x) {
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entry:
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%x.addr = alloca i64, align 4
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store i64 %x, i64* %x.addr, align 4
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call void @addrof_i64(i64* %x.addr)
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ret i64 %x
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}
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; CHECK-LABEL: _split_i64:
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; CHECK: pushl %ebp
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; CHECK: movl %esp, %ebp
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; CHECK: pushl %[[csr2:[^ ]*]]
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; CHECK: pushl %[[csr1:[^ ]*]]
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; CHECK: andl $-8, %esp
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; CHECK-DAG: movl 8(%ebp), %[[csr1]]
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; CHECK-DAG: movl 12(%ebp), %[[csr2]]
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2017-03-07 02:39:39 +08:00
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; CHECK-DAG: leal 8(%ebp), %[[reg:[^ ]*]]
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; CHECK: pushl %[[reg]]
|
Elide argument copies during instruction selection
Summary:
Avoids tons of prologue boilerplate when arguments are passed in memory
and left in memory. This can happen in a debug build or in a release
build when an argument alloca is escaped. This will dramatically affect
the code size of x86 debug builds, because X86 fast isel doesn't handle
arguments passed in memory at all. It only handles the x86_64 case of up
to 6 basic register parameters.
This is implemented by analyzing the entry block before ISel to identify
copy elision candidates. A copy elision candidate is an argument that is
used to fully initialize an alloca before any other possibly escaping
uses of that alloca. If an argument is a copy elision candidate, we set
a flag on the InputArg. If the the target generates loads from a fixed
stack object that matches the size and alignment requirements of the
alloca, the SelectionDAG builder will delete the stack object created
for the alloca and replace it with the fixed stack object. The load is
left behind to satisfy any remaining uses of the argument value. The
store is now dead and is therefore elided. The fixed stack object is
also marked as mutable, as it may now be modified by the user, and it
would be invalid to rematerialize the initial load from it.
Supersedes D28388
Fixes PR26328
Reviewers: chandlerc, MatzeB, qcolombet, inglorion, hans
Subscribers: igorb, llvm-commits
Differential Revision: https://reviews.llvm.org/D29668
llvm-svn: 296683
2017-03-02 05:42:00 +08:00
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; CHECK: calll _addrof_i64
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; CHECK-DAG: movl %[[csr1]], %eax
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; CHECK-DAG: movl %[[csr2]], %edx
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; CHECK: leal -8(%ebp), %esp
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; CHECK: popl %[[csr1]]
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; CHECK: popl %[[csr2]]
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; CHECK: popl %ebp
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; CHECK: retl
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2017-03-04 09:40:40 +08:00
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define i1 @i1_arg(i1 %x) {
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%x.addr = alloca i1
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store i1 %x, i1* %x.addr
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call void @addrof_i1(i1* %x.addr)
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ret i1 %x
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}
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; CHECK-LABEL: _i1_arg:
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; CHECK: pushl %ebx
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; CHECK: movb 8(%esp), %bl
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; CHECK: leal 8(%esp), %eax
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; CHECK: pushl %eax
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; CHECK: calll _addrof_i1
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; CHECK: addl $4, %esp
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; CHECK: movl %ebx, %eax
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; CHECK: popl %ebx
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|
; CHECK: retl
|
Elide argument copies during instruction selection
Summary:
Avoids tons of prologue boilerplate when arguments are passed in memory
and left in memory. This can happen in a debug build or in a release
build when an argument alloca is escaped. This will dramatically affect
the code size of x86 debug builds, because X86 fast isel doesn't handle
arguments passed in memory at all. It only handles the x86_64 case of up
to 6 basic register parameters.
This is implemented by analyzing the entry block before ISel to identify
copy elision candidates. A copy elision candidate is an argument that is
used to fully initialize an alloca before any other possibly escaping
uses of that alloca. If an argument is a copy elision candidate, we set
a flag on the InputArg. If the the target generates loads from a fixed
stack object that matches the size and alignment requirements of the
alloca, the SelectionDAG builder will delete the stack object created
for the alloca and replace it with the fixed stack object. The load is
left behind to satisfy any remaining uses of the argument value. The
store is now dead and is therefore elided. The fixed stack object is
also marked as mutable, as it may now be modified by the user, and it
would be invalid to rematerialize the initial load from it.
Supersedes D28388
Fixes PR26328
Reviewers: chandlerc, MatzeB, qcolombet, inglorion, hans
Subscribers: igorb, llvm-commits
Differential Revision: https://reviews.llvm.org/D29668
llvm-svn: 296683
2017-03-02 05:42:00 +08:00
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|
; We can't copy elide when an i64 is split between registers and memory in a
|
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|
; fastcc function.
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define fastcc i64 @fastcc_split_i64(i64* %p, i64 %x) {
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|
entry:
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%x.addr = alloca i64, align 4
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store i64 %x, i64* %x.addr, align 4
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call void @addrof_i64(i64* %x.addr)
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ret i64 %x
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}
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|
; CHECK-LABEL: _fastcc_split_i64:
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|
; CHECK: pushl %ebp
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; CHECK: movl %esp, %ebp
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; CHECK-DAG: movl %edx, %[[r1:[^ ]*]]
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; CHECK-DAG: movl 8(%ebp), %[[r2:[^ ]*]]
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|
; CHECK-DAG: movl %[[r2]], 4(%esp)
|
2018-02-28 00:59:10 +08:00
|
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|
; CHECK-DAG: movl %edx, (%esp)
|
Elide argument copies during instruction selection
Summary:
Avoids tons of prologue boilerplate when arguments are passed in memory
and left in memory. This can happen in a debug build or in a release
build when an argument alloca is escaped. This will dramatically affect
the code size of x86 debug builds, because X86 fast isel doesn't handle
arguments passed in memory at all. It only handles the x86_64 case of up
to 6 basic register parameters.
This is implemented by analyzing the entry block before ISel to identify
copy elision candidates. A copy elision candidate is an argument that is
used to fully initialize an alloca before any other possibly escaping
uses of that alloca. If an argument is a copy elision candidate, we set
a flag on the InputArg. If the the target generates loads from a fixed
stack object that matches the size and alignment requirements of the
alloca, the SelectionDAG builder will delete the stack object created
for the alloca and replace it with the fixed stack object. The load is
left behind to satisfy any remaining uses of the argument value. The
store is now dead and is therefore elided. The fixed stack object is
also marked as mutable, as it may now be modified by the user, and it
would be invalid to rematerialize the initial load from it.
Supersedes D28388
Fixes PR26328
Reviewers: chandlerc, MatzeB, qcolombet, inglorion, hans
Subscribers: igorb, llvm-commits
Differential Revision: https://reviews.llvm.org/D29668
llvm-svn: 296683
2017-03-02 05:42:00 +08:00
|
|
|
; CHECK: movl %esp, %[[reg:[^ ]*]]
|
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|
|
|
; CHECK: pushl %[[reg]]
|
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|
|
; CHECK: calll _addrof_i64
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|
; CHECK: popl %ebp
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|
; CHECK: retl
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; We can't copy elide when it would reduce the user requested alignment.
|
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|
define void @high_alignment(i32 %x) {
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entry:
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|
|
%x.p = alloca i32, align 128
|
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|
|
store i32 %x, i32* %x.p
|
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|
|
call void @addrof_i32(i32* %x.p)
|
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|
|
ret void
|
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|
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|
}
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|
|
|
; CHECK-LABEL: _high_alignment:
|
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|
|
; CHECK: andl $-128, %esp
|
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|
|
; CHECK: movl 8(%ebp), %[[reg:[^ ]*]]
|
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|
|
|
; CHECK: movl %[[reg]], (%esp)
|
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|
; CHECK: movl %esp, %[[reg:[^ ]*]]
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|
; CHECK: pushl %[[reg]]
|
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|
|
; CHECK: calll _addrof_i32
|
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|
; CHECK: retl
|
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|
|
|
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|
|
|
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|
|
|
; We can't copy elide when it would reduce the ABI required alignment.
|
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|
|
|
; FIXME: We should lower the ABI alignment of i64 on Windows, since MSVC
|
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|
|
|
; doesn't guarantee it.
|
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|
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|
|
|
|
|
define void @abi_alignment(i64 %x) {
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|
|
|
entry:
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|
|
|
%x.p = alloca i64
|
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|
|
|
store i64 %x, i64* %x.p
|
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|
|
|
call void @addrof_i64(i64* %x.p)
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|
ret void
|
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|
|
}
|
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|
|
|
|
|
|
|
|
; CHECK-LABEL: _abi_alignment:
|
|
|
|
|
; CHECK: andl $-8, %esp
|
|
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|
|
; CHECK: movl 8(%ebp), %[[reg:[^ ]*]]
|
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|
|
|
; CHECK: movl %[[reg]], (%esp)
|
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|
|
; CHECK: movl %esp, %[[reg:[^ ]*]]
|
|
|
|
|
; CHECK: pushl %[[reg]]
|
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|
|
|
; CHECK: calll _addrof_i64
|
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|
; CHECK: retl
|
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|
|
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|
|
|
|
|
|
|
|
|
; The code we generate for this is unimportant. This is mostly a crash test.
|
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|
|
|
|
|
|
|
define void @split_i128(i128* %sret, i128 %x) {
|
|
|
|
|
entry:
|
|
|
|
|
%x.addr = alloca i128
|
|
|
|
|
store i128 %x, i128* %x.addr
|
|
|
|
|
call void @addrof_i128(i128* %x.addr)
|
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|
|
|
store i128 %x, i128* %sret
|
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|
|
|
ret void
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; CHECK-LABEL: _split_i128:
|
|
|
|
|
; CHECK: pushl %ebp
|
|
|
|
|
; CHECK: calll _addrof_i128
|
|
|
|
|
; CHECK: retl
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
; Check that we load all of x, y, and z before the call.
|
|
|
|
|
|
|
|
|
|
define i32 @three_args(i32 %x, i32 %y, i32 %z) {
|
|
|
|
|
entry:
|
|
|
|
|
%z.addr = alloca i32, align 4
|
|
|
|
|
%y.addr = alloca i32, align 4
|
|
|
|
|
%x.addr = alloca i32, align 4
|
|
|
|
|
store i32 %z, i32* %z.addr, align 4
|
|
|
|
|
store i32 %y, i32* %y.addr, align 4
|
|
|
|
|
store i32 %x, i32* %x.addr, align 4
|
|
|
|
|
call void @addrof_i32_x3(i32* %x.addr, i32* %y.addr, i32* %z.addr)
|
|
|
|
|
%s1 = add i32 %x, %y
|
|
|
|
|
%sum = add i32 %s1, %z
|
|
|
|
|
ret i32 %sum
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; CHECK-LABEL: _three_args:
|
|
|
|
|
; CHECK: pushl %[[csr:[^ ]*]]
|
|
|
|
|
; CHECK-DAG: movl {{[0-9]+}}(%esp), %[[csr]]
|
|
|
|
|
; CHECK-DAG: addl {{[0-9]+}}(%esp), %[[csr]]
|
|
|
|
|
; CHECK-DAG: addl {{[0-9]+}}(%esp), %[[csr]]
|
|
|
|
|
; CHECK-DAG: leal 8(%esp), %[[x:[^ ]*]]
|
|
|
|
|
; CHECK-DAG: leal 12(%esp), %[[y:[^ ]*]]
|
|
|
|
|
; CHECK-DAG: leal 16(%esp), %[[z:[^ ]*]]
|
|
|
|
|
; CHECK: pushl %[[z]]
|
|
|
|
|
; CHECK: pushl %[[y]]
|
|
|
|
|
; CHECK: pushl %[[x]]
|
|
|
|
|
; CHECK: calll _addrof_i32_x3
|
|
|
|
|
; CHECK: movl %[[csr]], %eax
|
|
|
|
|
; CHECK: popl %[[csr]]
|
|
|
|
|
; CHECK: retl
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
define void @two_args_same_alloca(i32 %x, i32 %y) {
|
|
|
|
|
entry:
|
|
|
|
|
%x.addr = alloca i32
|
|
|
|
|
store i32 %x, i32* %x.addr
|
|
|
|
|
store i32 %y, i32* %x.addr
|
|
|
|
|
call void @addrof_i32(i32* %x.addr)
|
|
|
|
|
ret void
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; CHECK-LABEL: _two_args_same_alloca:
|
|
|
|
|
; CHECK: movl 8(%esp), {{.*}}
|
|
|
|
|
; CHECK: movl {{.*}}, 4(%esp)
|
|
|
|
|
; CHECK: leal 4(%esp), %[[reg:[^ ]*]]
|
|
|
|
|
; CHECK: pushl %[[reg]]
|
|
|
|
|
; CHECK: calll _addrof_i32
|
|
|
|
|
; CHECK: retl
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
define void @avoid_byval(i32* byval %x) {
|
|
|
|
|
entry:
|
|
|
|
|
%x.p.p = alloca i32*
|
|
|
|
|
store i32* %x, i32** %x.p.p
|
|
|
|
|
call void @addrof_i32(i32* %x)
|
|
|
|
|
ret void
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; CHECK-LABEL: _avoid_byval:
|
|
|
|
|
; CHECK: leal {{[0-9]+}}(%esp), %[[reg:[^ ]*]]
|
|
|
|
|
; CHECK: pushl %[[reg]]
|
|
|
|
|
; CHECK: calll _addrof_i32
|
|
|
|
|
; CHECK: retl
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
define void @avoid_inalloca(i32* inalloca %x) {
|
|
|
|
|
entry:
|
|
|
|
|
%x.p.p = alloca i32*
|
|
|
|
|
store i32* %x, i32** %x.p.p
|
|
|
|
|
call void @addrof_i32(i32* %x)
|
|
|
|
|
ret void
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; CHECK-LABEL: _avoid_inalloca:
|
|
|
|
|
; CHECK: leal {{[0-9]+}}(%esp), %[[reg:[^ ]*]]
|
|
|
|
|
; CHECK: pushl %[[reg]]
|
|
|
|
|
; CHECK: calll _addrof_i32
|
|
|
|
|
; CHECK: retl
|
|
|
|
|
|
|
|
|
|
; Don't elide the copy when the alloca is escaped with a store.
|
|
|
|
|
define void @escape_with_store(i32 %x) {
|
|
|
|
|
%x1 = alloca i32
|
|
|
|
|
%x2 = alloca i32*
|
|
|
|
|
store i32* %x1, i32** %x2
|
|
|
|
|
%x3 = load i32*, i32** %x2
|
|
|
|
|
store i32 0, i32* %x3
|
|
|
|
|
store i32 %x, i32* %x1
|
|
|
|
|
call void @addrof_i32(i32* %x1)
|
|
|
|
|
ret void
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; CHECK-LABEL: _escape_with_store:
|
Elide stores which are overwritten without being observed.
Summary:
In SelectionDAG, when a store is immediately chained to another store
to the same address, elide the first store as it has no observable
effects. This is causes small improvements dealing with intrinsics
lowered to stores.
Test notes:
* Many testcases overwrite store addresses multiple times and needed
minor changes, mainly making stores volatile to prevent the
optimization from optimizing the test away.
* Many X86 test cases optimized out instructions associated with
associated with va_start.
* Note that test_splat in CodeGen/AArch64/misched-stp.ll no longer has
dependencies to check and can probably be removed and potentially
replaced with another test.
Reviewers: rnk, john.brawn
Subscribers: aemerson, rengolin, qcolombet, jyknight, nemanjai, nhaehnle, javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D33206
llvm-svn: 303198
2017-05-17 03:43:56 +08:00
|
|
|
; CHECK: movl {{.*}}(%esp), %[[reg:[^ ]*]]
|
|
|
|
|
; CHECK: movl %[[reg]], [[offs:[0-9]*]](%esp)
|
Elide argument copies during instruction selection
Summary:
Avoids tons of prologue boilerplate when arguments are passed in memory
and left in memory. This can happen in a debug build or in a release
build when an argument alloca is escaped. This will dramatically affect
the code size of x86 debug builds, because X86 fast isel doesn't handle
arguments passed in memory at all. It only handles the x86_64 case of up
to 6 basic register parameters.
This is implemented by analyzing the entry block before ISel to identify
copy elision candidates. A copy elision candidate is an argument that is
used to fully initialize an alloca before any other possibly escaping
uses of that alloca. If an argument is a copy elision candidate, we set
a flag on the InputArg. If the the target generates loads from a fixed
stack object that matches the size and alignment requirements of the
alloca, the SelectionDAG builder will delete the stack object created
for the alloca and replace it with the fixed stack object. The load is
left behind to satisfy any remaining uses of the argument value. The
store is now dead and is therefore elided. The fixed stack object is
also marked as mutable, as it may now be modified by the user, and it
would be invalid to rematerialize the initial load from it.
Supersedes D28388
Fixes PR26328
Reviewers: chandlerc, MatzeB, qcolombet, inglorion, hans
Subscribers: igorb, llvm-commits
Differential Revision: https://reviews.llvm.org/D29668
llvm-svn: 296683
2017-03-02 05:42:00 +08:00
|
|
|
; CHECK: calll _addrof_i32
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
; This test case exposed issues with the use of TokenFactor.
|
|
|
|
|
|
|
|
|
|
define void @sret_and_elide(i32* sret %sret, i32 %v) {
|
|
|
|
|
%v.p = alloca i32
|
|
|
|
|
store i32 %v, i32* %v.p
|
|
|
|
|
call void @addrof_i32(i32* %v.p)
|
|
|
|
|
store i32 %v, i32* %sret
|
|
|
|
|
ret void
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; CHECK-LABEL: _sret_and_elide:
|
|
|
|
|
; CHECK: pushl
|
|
|
|
|
; CHECK: pushl
|
|
|
|
|
; CHECK: movl 12(%esp), %[[sret:[^ ]*]]
|
|
|
|
|
; CHECK: movl 16(%esp), %[[v:[^ ]*]]
|
|
|
|
|
; CHECK: leal 16(%esp), %[[reg:[^ ]*]]
|
|
|
|
|
; CHECK: pushl %[[reg]]
|
|
|
|
|
; CHECK: calll _addrof_i32
|
|
|
|
|
; CHECK: movl %[[v]], (%[[sret]])
|
|
|
|
|
; CHECK: movl %[[sret]], %eax
|
|
|
|
|
; CHECK: popl
|
|
|
|
|
; CHECK: popl
|
|
|
|
|
; CHECK: retl
|