Optimize RoboCaller::AddReceiver() for code size
Essentially, instead of having the inlined UntypedFunction::Create(f)
return an UntypedFunction which is then passed as an argument to
non-inlined RoboCallerReceivers::AddReceiverImpl(), we let
UntypedFunction::PrepareArgs(f) return a few different kinds of
trivial structs (depending on what sort of type f has) which are
passed as arguments to non-inlined RoboCallerReceivers::AddReceiver()
(which then converts them to UntypedFunction by calling
UntypedFunction::Create()). These structs are smaller than
UntypedFunction and optimized for argument passing, so many fewer
instructions are needed.
Example code:
struct Foo {
void Receive(int, float, int, float);
void TestAddLambdaReceiver();
webrtc::RoboCaller<int, float, int, float> rc;
};
void Foo::TestAddLambdaReceiver() {
rc.AddReceiver([this](int a, float b, int c, float d){
Receive(a, b, c, d);});
}
On arm32, we get before this CL:
Foo::TestAddLambdaReceiver():
push {r11, lr}
mov r11, sp
sub sp, sp, #24
ldr r1, .LCPI0_0
mov r2, #0
stm sp, {r0, r2}
add r1, pc, r1
str r2, [sp, #20]
str r1, [sp, #16]
mov r1, sp
bl RoboCallerReceivers::AddReceiverImpl
mov sp, r11
pop {r11, pc}
.LCPI0_0:
.long CallInlineStorage<Foo::TestAddLambdaReceiver()::$_0>
CallInlineStorage<Foo::TestAddLambdaReceiver()::$_0>:
ldr r0, [r0]
b Foo::Receive(int, float, int, float)
After this CL:
Foo::TestAddLambdaReceiver():
ldr r3, .LCPI0_0
mov r2, r0
add r3, pc, r3
b RoboCallerReceivers::AddReceiver<1u>
.LCPI0_0:
.long CallInlineStorage<Foo::TestAddLambdaReceiver()::$_0>
CallInlineStorage<Foo::TestAddLambdaReceiver()::$_0>:
ldr r0, [r0]
b Foo::Receive(int, float, int, float)
(Symbol names abbreviated so that they'll fit on one line.)
So a reduction from 64 to 28 bytes. The improvements on arm64 and
x86_64 are similar.
Bug: webrtc:11943
Change-Id: I93fbba083be0235051c3279d3e3f6852a4a9fdad
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/185960
Commit-Queue: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32244}
diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index a09c06e..489a5c6 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -57,6 +57,7 @@
":untyped_function",
"../api:function_view",
"system:assume",
+ "system:inline",
]
}
