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Ayke van Laethem
2bb70812a8
This patch adds a new pragma for functions and globals to set the
section name. This can be useful to place a function or global in a
special device specific section, for example:
* Functions may be placed in RAM to make them run faster, or in flash
(if RAM is the default) to not let them take up RAM.
* DMA memory may only be placed in a special memory area.
* Some RAM may be faster than other RAM, and some globals may be
performance critical thus placing them in this special RAM area can
help.
* Some (large) global variables may need to be placed in external RAM,
which can be done by placing them in a special section.
To use it, you have to place a function or global in a special section,
for example:
//go:section .externalram
var externalRAMBuffer [1024]byte
This can then be placed in a special section of the linker script, for
example something like this:
.bss.extram (NOLOAD) : {
*(.externalram)
} > ERAM
35 lines
1.1 KiB
Go
35 lines
1.1 KiB
Go
package transform
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import "tinygo.org/x/go-llvm"
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// This file implements small transformations on globals (functions and global
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// variables) for specific ABIs/architectures.
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// ApplyFunctionSections puts every function in a separate section. This makes
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// it possible for the linker to remove dead code. It is the equivalent of
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// passing -ffunction-sections to a C compiler.
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func ApplyFunctionSections(mod llvm.Module) {
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llvmFn := mod.FirstFunction()
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for !llvmFn.IsNil() {
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if !llvmFn.IsDeclaration() && llvmFn.Section() == "" {
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name := llvmFn.Name()
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llvmFn.SetSection(".text." + name)
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}
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llvmFn = llvm.NextFunction(llvmFn)
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}
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}
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// DisableTailCalls adds the "disable-tail-calls"="true" function attribute to
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// all functions. This may be necessary, in particular to avoid an error with
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// WebAssembly in LLVM 11.
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func DisableTailCalls(mod llvm.Module) {
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attribute := mod.Context().CreateStringAttribute("disable-tail-calls", "true")
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llvmFn := mod.FirstFunction()
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for !llvmFn.IsNil() {
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if !llvmFn.IsDeclaration() {
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llvmFn.AddFunctionAttr(attribute)
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}
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llvmFn = llvm.NextFunction(llvmFn)
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}
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}
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