2015-11-24 05:33:58 +08:00
|
|
|
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
|
2015-10-15 05:47:03 +08:00
|
|
|
; RUN: llc < %s -mtriple=x86_64-unknown-unknown | FileCheck %s
|
|
|
|
|
|
|
|
|
|
; The fundamental problem: an add separated from other arithmetic by a sext can't
|
[x86] promote 'add nsw' to a wider type to allow more combines
The motivation for this patch starts with PR20134:
https://llvm.org/bugs/show_bug.cgi?id=20134
void foo(int *a, int i) {
a[i] = a[i+1] + a[i+2];
}
It seems better to produce this (14 bytes):
movslq %esi, %rsi
movl 0x4(%rdi,%rsi,4), %eax
addl 0x8(%rdi,%rsi,4), %eax
movl %eax, (%rdi,%rsi,4)
Rather than this (22 bytes):
leal 0x1(%rsi), %eax
cltq
leal 0x2(%rsi), %ecx
movslq %ecx, %rcx
movl (%rdi,%rcx,4), %ecx
addl (%rdi,%rax,4), %ecx
movslq %esi, %rax
movl %ecx, (%rdi,%rax,4)
The most basic problem (the first test case in the patch combines constants) should also be fixed in InstCombine,
but it gets more complicated after that because we need to consider architecture and micro-architecture. For
example, AArch64 may not see any benefit from the more general transform because the ISA solves the sexting in
hardware. Some x86 chips may not want to replace 2 ADD insts with 1 LEA, and there's an attribute for that:
FeatureSlowLEA. But I suspect that doesn't go far enough or maybe it's not getting used when it should; I'm
also not sure if FeatureSlowLEA should also mean "slow complex addressing mode".
I see no perf differences on test-suite with this change running on AMD Jaguar, but I see small code size
improvements when building clang and the LLVM tools with the patched compiler.
A more general solution to the sext(add nsw(x, C)) problem that works for multiple targets is available
in CodeGenPrepare, but it may take quite a bit more work to get that to fire on all of the test cases that
this patch takes care of.
Differential Revision: http://reviews.llvm.org/D13757
llvm-svn: 250560
2015-10-17 06:14:12 +08:00
|
|
|
; be combined with the later instructions. However, if the first add is 'nsw',
|
2015-10-15 05:47:03 +08:00
|
|
|
; then we can promote the sext ahead of that add to allow optimizations.
|
|
|
|
|
|
|
|
|
|
define i64 @add_nsw_consts(i32 %i) {
|
|
|
|
|
; CHECK-LABEL: add_nsw_consts:
|
|
|
|
|
; CHECK: # BB#0:
|
|
|
|
|
; CHECK-NEXT: movslq %edi, %rax
|
[x86] promote 'add nsw' to a wider type to allow more combines
The motivation for this patch starts with PR20134:
https://llvm.org/bugs/show_bug.cgi?id=20134
void foo(int *a, int i) {
a[i] = a[i+1] + a[i+2];
}
It seems better to produce this (14 bytes):
movslq %esi, %rsi
movl 0x4(%rdi,%rsi,4), %eax
addl 0x8(%rdi,%rsi,4), %eax
movl %eax, (%rdi,%rsi,4)
Rather than this (22 bytes):
leal 0x1(%rsi), %eax
cltq
leal 0x2(%rsi), %ecx
movslq %ecx, %rcx
movl (%rdi,%rcx,4), %ecx
addl (%rdi,%rax,4), %ecx
movslq %esi, %rax
movl %ecx, (%rdi,%rax,4)
The most basic problem (the first test case in the patch combines constants) should also be fixed in InstCombine,
but it gets more complicated after that because we need to consider architecture and micro-architecture. For
example, AArch64 may not see any benefit from the more general transform because the ISA solves the sexting in
hardware. Some x86 chips may not want to replace 2 ADD insts with 1 LEA, and there's an attribute for that:
FeatureSlowLEA. But I suspect that doesn't go far enough or maybe it's not getting used when it should; I'm
also not sure if FeatureSlowLEA should also mean "slow complex addressing mode".
I see no perf differences on test-suite with this change running on AMD Jaguar, but I see small code size
improvements when building clang and the LLVM tools with the patched compiler.
A more general solution to the sext(add nsw(x, C)) problem that works for multiple targets is available
in CodeGenPrepare, but it may take quite a bit more work to get that to fire on all of the test cases that
this patch takes care of.
Differential Revision: http://reviews.llvm.org/D13757
llvm-svn: 250560
2015-10-17 06:14:12 +08:00
|
|
|
; CHECK-NEXT: addq $12, %rax
|
2015-10-15 05:47:03 +08:00
|
|
|
; CHECK-NEXT: retq
|
|
|
|
|
|
|
|
|
|
%add = add nsw i32 %i, 5
|
|
|
|
|
%ext = sext i32 %add to i64
|
|
|
|
|
%idx = add i64 %ext, 7
|
|
|
|
|
ret i64 %idx
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; An x86 bonus: If we promote the sext ahead of the 'add nsw',
|
|
|
|
|
; we allow LEA formation and eliminate an add instruction.
|
|
|
|
|
|
|
|
|
|
define i64 @add_nsw_sext_add(i32 %i, i64 %x) {
|
|
|
|
|
; CHECK-LABEL: add_nsw_sext_add:
|
|
|
|
|
; CHECK: # BB#0:
|
|
|
|
|
; CHECK-NEXT: movslq %edi, %rax
|
2016-02-28 03:57:45 +08:00
|
|
|
; CHECK-NEXT: leaq 5(%rsi,%rax), %rax
|
2015-10-15 05:47:03 +08:00
|
|
|
; CHECK-NEXT: retq
|
|
|
|
|
|
|
|
|
|
%add = add nsw i32 %i, 5
|
|
|
|
|
%ext = sext i32 %add to i64
|
|
|
|
|
%idx = add i64 %x, %ext
|
|
|
|
|
ret i64 %idx
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; Throw in a scale (left shift) because an LEA can do that too.
|
|
|
|
|
; Use a negative constant (LEA displacement) to verify that's handled correctly.
|
|
|
|
|
|
|
|
|
|
define i64 @add_nsw_sext_lsh_add(i32 %i, i64 %x) {
|
|
|
|
|
; CHECK-LABEL: add_nsw_sext_lsh_add:
|
|
|
|
|
; CHECK: # BB#0:
|
|
|
|
|
; CHECK-NEXT: movslq %edi, %rax
|
[x86] promote 'add nsw' to a wider type to allow more combines
The motivation for this patch starts with PR20134:
https://llvm.org/bugs/show_bug.cgi?id=20134
void foo(int *a, int i) {
a[i] = a[i+1] + a[i+2];
}
It seems better to produce this (14 bytes):
movslq %esi, %rsi
movl 0x4(%rdi,%rsi,4), %eax
addl 0x8(%rdi,%rsi,4), %eax
movl %eax, (%rdi,%rsi,4)
Rather than this (22 bytes):
leal 0x1(%rsi), %eax
cltq
leal 0x2(%rsi), %ecx
movslq %ecx, %rcx
movl (%rdi,%rcx,4), %ecx
addl (%rdi,%rax,4), %ecx
movslq %esi, %rax
movl %ecx, (%rdi,%rax,4)
The most basic problem (the first test case in the patch combines constants) should also be fixed in InstCombine,
but it gets more complicated after that because we need to consider architecture and micro-architecture. For
example, AArch64 may not see any benefit from the more general transform because the ISA solves the sexting in
hardware. Some x86 chips may not want to replace 2 ADD insts with 1 LEA, and there's an attribute for that:
FeatureSlowLEA. But I suspect that doesn't go far enough or maybe it's not getting used when it should; I'm
also not sure if FeatureSlowLEA should also mean "slow complex addressing mode".
I see no perf differences on test-suite with this change running on AMD Jaguar, but I see small code size
improvements when building clang and the LLVM tools with the patched compiler.
A more general solution to the sext(add nsw(x, C)) problem that works for multiple targets is available
in CodeGenPrepare, but it may take quite a bit more work to get that to fire on all of the test cases that
this patch takes care of.
Differential Revision: http://reviews.llvm.org/D13757
llvm-svn: 250560
2015-10-17 06:14:12 +08:00
|
|
|
; CHECK-NEXT: leaq -40(%rsi,%rax,8), %rax
|
2015-10-15 05:47:03 +08:00
|
|
|
; CHECK-NEXT: retq
|
|
|
|
|
|
|
|
|
|
%add = add nsw i32 %i, -5
|
|
|
|
|
%ext = sext i32 %add to i64
|
|
|
|
|
%shl = shl i64 %ext, 3
|
|
|
|
|
%idx = add i64 %x, %shl
|
|
|
|
|
ret i64 %idx
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; Don't promote the sext if it has no users. The wider add instruction needs an
|
|
|
|
|
; extra byte to encode.
|
|
|
|
|
|
|
|
|
|
define i64 @add_nsw_sext(i32 %i, i64 %x) {
|
|
|
|
|
; CHECK-LABEL: add_nsw_sext:
|
|
|
|
|
; CHECK: # BB#0:
|
|
|
|
|
; CHECK-NEXT: addl $5, %edi
|
|
|
|
|
; CHECK-NEXT: movslq %edi, %rax
|
|
|
|
|
; CHECK-NEXT: retq
|
|
|
|
|
|
|
|
|
|
%add = add nsw i32 %i, 5
|
|
|
|
|
%ext = sext i32 %add to i64
|
|
|
|
|
ret i64 %ext
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; The typical use case: a 64-bit system where an 'int' is used as an index into an array.
|
|
|
|
|
|
|
|
|
|
define i8* @gep8(i32 %i, i8* %x) {
|
|
|
|
|
; CHECK-LABEL: gep8:
|
|
|
|
|
; CHECK: # BB#0:
|
|
|
|
|
; CHECK-NEXT: movslq %edi, %rax
|
2016-02-28 03:57:45 +08:00
|
|
|
; CHECK-NEXT: leaq 5(%rsi,%rax), %rax
|
2015-10-15 05:47:03 +08:00
|
|
|
; CHECK-NEXT: retq
|
|
|
|
|
|
|
|
|
|
%add = add nsw i32 %i, 5
|
|
|
|
|
%ext = sext i32 %add to i64
|
|
|
|
|
%idx = getelementptr i8, i8* %x, i64 %ext
|
|
|
|
|
ret i8* %idx
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
define i16* @gep16(i32 %i, i16* %x) {
|
|
|
|
|
; CHECK-LABEL: gep16:
|
|
|
|
|
; CHECK: # BB#0:
|
|
|
|
|
; CHECK-NEXT: movslq %edi, %rax
|
[x86] promote 'add nsw' to a wider type to allow more combines
The motivation for this patch starts with PR20134:
https://llvm.org/bugs/show_bug.cgi?id=20134
void foo(int *a, int i) {
a[i] = a[i+1] + a[i+2];
}
It seems better to produce this (14 bytes):
movslq %esi, %rsi
movl 0x4(%rdi,%rsi,4), %eax
addl 0x8(%rdi,%rsi,4), %eax
movl %eax, (%rdi,%rsi,4)
Rather than this (22 bytes):
leal 0x1(%rsi), %eax
cltq
leal 0x2(%rsi), %ecx
movslq %ecx, %rcx
movl (%rdi,%rcx,4), %ecx
addl (%rdi,%rax,4), %ecx
movslq %esi, %rax
movl %ecx, (%rdi,%rax,4)
The most basic problem (the first test case in the patch combines constants) should also be fixed in InstCombine,
but it gets more complicated after that because we need to consider architecture and micro-architecture. For
example, AArch64 may not see any benefit from the more general transform because the ISA solves the sexting in
hardware. Some x86 chips may not want to replace 2 ADD insts with 1 LEA, and there's an attribute for that:
FeatureSlowLEA. But I suspect that doesn't go far enough or maybe it's not getting used when it should; I'm
also not sure if FeatureSlowLEA should also mean "slow complex addressing mode".
I see no perf differences on test-suite with this change running on AMD Jaguar, but I see small code size
improvements when building clang and the LLVM tools with the patched compiler.
A more general solution to the sext(add nsw(x, C)) problem that works for multiple targets is available
in CodeGenPrepare, but it may take quite a bit more work to get that to fire on all of the test cases that
this patch takes care of.
Differential Revision: http://reviews.llvm.org/D13757
llvm-svn: 250560
2015-10-17 06:14:12 +08:00
|
|
|
; CHECK-NEXT: leaq -10(%rsi,%rax,2), %rax
|
2015-10-15 05:47:03 +08:00
|
|
|
; CHECK-NEXT: retq
|
|
|
|
|
|
|
|
|
|
%add = add nsw i32 %i, -5
|
|
|
|
|
%ext = sext i32 %add to i64
|
|
|
|
|
%idx = getelementptr i16, i16* %x, i64 %ext
|
|
|
|
|
ret i16* %idx
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
define i32* @gep32(i32 %i, i32* %x) {
|
|
|
|
|
; CHECK-LABEL: gep32:
|
|
|
|
|
; CHECK: # BB#0:
|
|
|
|
|
; CHECK-NEXT: movslq %edi, %rax
|
[x86] promote 'add nsw' to a wider type to allow more combines
The motivation for this patch starts with PR20134:
https://llvm.org/bugs/show_bug.cgi?id=20134
void foo(int *a, int i) {
a[i] = a[i+1] + a[i+2];
}
It seems better to produce this (14 bytes):
movslq %esi, %rsi
movl 0x4(%rdi,%rsi,4), %eax
addl 0x8(%rdi,%rsi,4), %eax
movl %eax, (%rdi,%rsi,4)
Rather than this (22 bytes):
leal 0x1(%rsi), %eax
cltq
leal 0x2(%rsi), %ecx
movslq %ecx, %rcx
movl (%rdi,%rcx,4), %ecx
addl (%rdi,%rax,4), %ecx
movslq %esi, %rax
movl %ecx, (%rdi,%rax,4)
The most basic problem (the first test case in the patch combines constants) should also be fixed in InstCombine,
but it gets more complicated after that because we need to consider architecture and micro-architecture. For
example, AArch64 may not see any benefit from the more general transform because the ISA solves the sexting in
hardware. Some x86 chips may not want to replace 2 ADD insts with 1 LEA, and there's an attribute for that:
FeatureSlowLEA. But I suspect that doesn't go far enough or maybe it's not getting used when it should; I'm
also not sure if FeatureSlowLEA should also mean "slow complex addressing mode".
I see no perf differences on test-suite with this change running on AMD Jaguar, but I see small code size
improvements when building clang and the LLVM tools with the patched compiler.
A more general solution to the sext(add nsw(x, C)) problem that works for multiple targets is available
in CodeGenPrepare, but it may take quite a bit more work to get that to fire on all of the test cases that
this patch takes care of.
Differential Revision: http://reviews.llvm.org/D13757
llvm-svn: 250560
2015-10-17 06:14:12 +08:00
|
|
|
; CHECK-NEXT: leaq 20(%rsi,%rax,4), %rax
|
2015-10-15 05:47:03 +08:00
|
|
|
; CHECK-NEXT: retq
|
|
|
|
|
|
|
|
|
|
%add = add nsw i32 %i, 5
|
|
|
|
|
%ext = sext i32 %add to i64
|
|
|
|
|
%idx = getelementptr i32, i32* %x, i64 %ext
|
|
|
|
|
ret i32* %idx
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
define i64* @gep64(i32 %i, i64* %x) {
|
|
|
|
|
; CHECK-LABEL: gep64:
|
|
|
|
|
; CHECK: # BB#0:
|
|
|
|
|
; CHECK-NEXT: movslq %edi, %rax
|
[x86] promote 'add nsw' to a wider type to allow more combines
The motivation for this patch starts with PR20134:
https://llvm.org/bugs/show_bug.cgi?id=20134
void foo(int *a, int i) {
a[i] = a[i+1] + a[i+2];
}
It seems better to produce this (14 bytes):
movslq %esi, %rsi
movl 0x4(%rdi,%rsi,4), %eax
addl 0x8(%rdi,%rsi,4), %eax
movl %eax, (%rdi,%rsi,4)
Rather than this (22 bytes):
leal 0x1(%rsi), %eax
cltq
leal 0x2(%rsi), %ecx
movslq %ecx, %rcx
movl (%rdi,%rcx,4), %ecx
addl (%rdi,%rax,4), %ecx
movslq %esi, %rax
movl %ecx, (%rdi,%rax,4)
The most basic problem (the first test case in the patch combines constants) should also be fixed in InstCombine,
but it gets more complicated after that because we need to consider architecture and micro-architecture. For
example, AArch64 may not see any benefit from the more general transform because the ISA solves the sexting in
hardware. Some x86 chips may not want to replace 2 ADD insts with 1 LEA, and there's an attribute for that:
FeatureSlowLEA. But I suspect that doesn't go far enough or maybe it's not getting used when it should; I'm
also not sure if FeatureSlowLEA should also mean "slow complex addressing mode".
I see no perf differences on test-suite with this change running on AMD Jaguar, but I see small code size
improvements when building clang and the LLVM tools with the patched compiler.
A more general solution to the sext(add nsw(x, C)) problem that works for multiple targets is available
in CodeGenPrepare, but it may take quite a bit more work to get that to fire on all of the test cases that
this patch takes care of.
Differential Revision: http://reviews.llvm.org/D13757
llvm-svn: 250560
2015-10-17 06:14:12 +08:00
|
|
|
; CHECK-NEXT: leaq -40(%rsi,%rax,8), %rax
|
2015-10-15 05:47:03 +08:00
|
|
|
; CHECK-NEXT: retq
|
|
|
|
|
|
|
|
|
|
%add = add nsw i32 %i, -5
|
|
|
|
|
%ext = sext i32 %add to i64
|
|
|
|
|
%idx = getelementptr i64, i64* %x, i64 %ext
|
|
|
|
|
ret i64* %idx
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; LEA can't scale by 16, but the adds can still be combined into an LEA.
|
|
|
|
|
|
|
|
|
|
define i128* @gep128(i32 %i, i128* %x) {
|
|
|
|
|
; CHECK-LABEL: gep128:
|
|
|
|
|
; CHECK: # BB#0:
|
|
|
|
|
; CHECK-NEXT: movslq %edi, %rax
|
|
|
|
|
; CHECK-NEXT: shlq $4, %rax
|
2016-02-28 03:57:45 +08:00
|
|
|
; CHECK-NEXT: leaq 80(%rsi,%rax), %rax
|
2015-10-15 05:47:03 +08:00
|
|
|
; CHECK-NEXT: retq
|
|
|
|
|
|
|
|
|
|
%add = add nsw i32 %i, 5
|
|
|
|
|
%ext = sext i32 %add to i64
|
|
|
|
|
%idx = getelementptr i128, i128* %x, i64 %ext
|
|
|
|
|
ret i128* %idx
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
; A bigger win can be achieved when there is more than one use of the
|
|
|
|
|
; sign extended value. In this case, we can eliminate sign extension
|
|
|
|
|
; instructions plus use more efficient addressing modes for memory ops.
|
|
|
|
|
|
|
|
|
|
define void @PR20134(i32* %a, i32 %i) {
|
|
|
|
|
; CHECK-LABEL: PR20134:
|
|
|
|
|
; CHECK: # BB#0:
|
[x86] promote 'add nsw' to a wider type to allow more combines
The motivation for this patch starts with PR20134:
https://llvm.org/bugs/show_bug.cgi?id=20134
void foo(int *a, int i) {
a[i] = a[i+1] + a[i+2];
}
It seems better to produce this (14 bytes):
movslq %esi, %rsi
movl 0x4(%rdi,%rsi,4), %eax
addl 0x8(%rdi,%rsi,4), %eax
movl %eax, (%rdi,%rsi,4)
Rather than this (22 bytes):
leal 0x1(%rsi), %eax
cltq
leal 0x2(%rsi), %ecx
movslq %ecx, %rcx
movl (%rdi,%rcx,4), %ecx
addl (%rdi,%rax,4), %ecx
movslq %esi, %rax
movl %ecx, (%rdi,%rax,4)
The most basic problem (the first test case in the patch combines constants) should also be fixed in InstCombine,
but it gets more complicated after that because we need to consider architecture and micro-architecture. For
example, AArch64 may not see any benefit from the more general transform because the ISA solves the sexting in
hardware. Some x86 chips may not want to replace 2 ADD insts with 1 LEA, and there's an attribute for that:
FeatureSlowLEA. But I suspect that doesn't go far enough or maybe it's not getting used when it should; I'm
also not sure if FeatureSlowLEA should also mean "slow complex addressing mode".
I see no perf differences on test-suite with this change running on AMD Jaguar, but I see small code size
improvements when building clang and the LLVM tools with the patched compiler.
A more general solution to the sext(add nsw(x, C)) problem that works for multiple targets is available
in CodeGenPrepare, but it may take quite a bit more work to get that to fire on all of the test cases that
this patch takes care of.
Differential Revision: http://reviews.llvm.org/D13757
llvm-svn: 250560
2015-10-17 06:14:12 +08:00
|
|
|
; CHECK-NEXT: movslq %esi, %rax
|
|
|
|
|
; CHECK-NEXT: movl 4(%rdi,%rax,4), %ecx
|
|
|
|
|
; CHECK-NEXT: addl 8(%rdi,%rax,4), %ecx
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; CHECK-NEXT: movl %ecx, (%rdi,%rax,4)
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2015-10-15 05:47:03 +08:00
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; CHECK-NEXT: retq
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%add1 = add nsw i32 %i, 1
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%idx1 = sext i32 %add1 to i64
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%gep1 = getelementptr i32, i32* %a, i64 %idx1
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%load1 = load i32, i32* %gep1, align 4
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%add2 = add nsw i32 %i, 2
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%idx2 = sext i32 %add2 to i64
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%gep2 = getelementptr i32, i32* %a, i64 %idx2
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%load2 = load i32, i32* %gep2, align 4
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%add3 = add i32 %load1, %load2
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%idx3 = sext i32 %i to i64
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%gep3 = getelementptr i32, i32* %a, i64 %idx3
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store i32 %add3, i32* %gep3, align 4
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ret void
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|
}
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