0b7957d612
This commit optimizes string literals and globals by setting the
appropriate alignment and using a nil pointer in zero-length strings.
- Setting the alignment for string values has a surprisingly large
effect, up to around 2% in binary size. I suspect that LLVM will
pick some default alignment for larger byte arrays if no alignment
has been specified and forcing an alignment of 1 will pack all
strings closer together.
- Using nil for zero-length strings also has a positive effect, but
I'm not sure why. Perhaps it makes some optimizations more trivial.
- Always setting the alignment on globals improves code size slightly,
probably for the same reasons setting the alignment of string
literals improves code size. The effect is much smaller, however.
This commit might have an effect on performance, but if it does this
should be tested separately and such a large win in binary size should
definitely not be ignored for small embedded systems.
71 строка
2,5 КиБ
LLVM
71 строка
2,5 КиБ
LLVM
; ModuleID = 'string.go'
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source_filename = "string.go"
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target datalayout = "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128"
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target triple = "i686--linux"
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%runtime._string = type { i8*, i32 }
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@"main.someString$string" = internal unnamed_addr constant [3 x i8] c"foo", align 1
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declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)
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define hidden void @main.init(i8* %context, i8* %parentHandle) unnamed_addr {
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entry:
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ret void
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}
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define hidden %runtime._string @main.someString(i8* %context, i8* %parentHandle) unnamed_addr {
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entry:
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ret %runtime._string { i8* getelementptr inbounds ([3 x i8], [3 x i8]* @"main.someString$string", i32 0, i32 0), i32 3 }
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}
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define hidden %runtime._string @main.zeroLengthString(i8* %context, i8* %parentHandle) unnamed_addr {
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entry:
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ret %runtime._string zeroinitializer
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}
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define hidden i32 @main.stringLen(i8* %s.data, i32 %s.len, i8* %context, i8* %parentHandle) unnamed_addr {
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entry:
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ret i32 %s.len
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}
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define hidden i8 @main.stringIndex(i8* %s.data, i32 %s.len, i32 %index, i8* %context, i8* %parentHandle) unnamed_addr {
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entry:
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%.not = icmp ult i32 %index, %s.len
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br i1 %.not, label %lookup.next, label %lookup.throw
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lookup.throw: ; preds = %entry
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call void @runtime.lookupPanic(i8* undef, i8* null)
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unreachable
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lookup.next: ; preds = %entry
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%0 = getelementptr inbounds i8, i8* %s.data, i32 %index
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%1 = load i8, i8* %0, align 1
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ret i8 %1
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}
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declare void @runtime.lookupPanic(i8*, i8*)
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define hidden i1 @main.stringCompareEqual(i8* %s1.data, i32 %s1.len, i8* %s2.data, i32 %s2.len, i8* %context, i8* %parentHandle) unnamed_addr {
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entry:
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%0 = call i1 @runtime.stringEqual(i8* %s1.data, i32 %s1.len, i8* %s2.data, i32 %s2.len, i8* undef, i8* null)
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ret i1 %0
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}
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declare i1 @runtime.stringEqual(i8*, i32, i8*, i32, i8*, i8*)
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define hidden i1 @main.stringCompareUnequal(i8* %s1.data, i32 %s1.len, i8* %s2.data, i32 %s2.len, i8* %context, i8* %parentHandle) unnamed_addr {
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entry:
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%0 = call i1 @runtime.stringEqual(i8* %s1.data, i32 %s1.len, i8* %s2.data, i32 %s2.len, i8* undef, i8* null)
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%1 = xor i1 %0, true
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ret i1 %1
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}
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define hidden i1 @main.stringCompareLarger(i8* %s1.data, i32 %s1.len, i8* %s2.data, i32 %s2.len, i8* %context, i8* %parentHandle) unnamed_addr {
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entry:
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%0 = call i1 @runtime.stringLess(i8* %s1.data, i32 %s1.len, i8* %s2.data, i32 %s2.len, i8* undef, i8* null)
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%1 = xor i1 %0, true
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ret i1 %1
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}
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declare i1 @runtime.stringLess(i8*, i32, i8*, i32, i8*, i8*)
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