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compiler: add alloc attributes to runtime.alloc

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This gives a small improvement now, and is needed to be able to use the
Heap2Stack transform that's available in the Attributor pass. This
Heap2Stack transform could replace our custom OptimizeAllocs pass.

Most of the changes are just IR that changed, the actual change is
relatively small.

To give an example of why this is useful, here is the code size before
this change:

    $ tinygo build -o test -size=short ./testdata/stdlib.go
       code    data     bss |   flash     ram
      95620    1812     968 |   97432    2780

    $ tinygo build -o test -size=short ./testdata/stdlib.go
       code    data     bss |   flash     ram
      95380    1812     968 |   97192    2780

That's a 0.25% reduction. Not a whole lot, but nice for such a small
patch.
This commit is contained in:
Ayke van Laethem
2023-03-11 20:57:40 +01:00
committed by Ron Evans
parent 5ed0cecf0d
commit f180339d6b
17 changed files with 504 additions and 447 deletions
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compiler/symbol.go
+25
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@@ -52,6 +52,17 @@ const (
inlineNone
)
// Values for the allockind attribute. Source:
// https://github.com/llvm/llvm-project/blob/release/16.x/llvm/include/llvm/IR/Attributes.h#L49
const (
allocKindAlloc = 1 << iota
allocKindRealloc
allocKindFree
allocKindUninitialized
allocKindZeroed
allocKindAligned
)
// getFunction returns the LLVM function for the given *ssa.Function, creating
// it if needed. It can later be filled with compilerContext.createFunction().
func (c *compilerContext) getFunction(fn *ssa.Function) (llvm.Type, llvm.Value) {
@@ -133,6 +144,20 @@ func (c *compilerContext) getFunction(fn *ssa.Function) (llvm.Type, llvm.Value)
for _, attrName := range []string{"noalias", "nonnull"} {
llvmFn.AddAttributeAtIndex(0, c.ctx.CreateEnumAttribute(llvm.AttributeKindID(attrName), 0))
}
if llvmutil.Major() >= 15 { // allockind etc are not available in LLVM 14
// Add attributes to signal to LLVM that this is an allocator
// function. This enables a number of optimizations.
llvmFn.AddFunctionAttr(c.ctx.CreateEnumAttribute(llvm.AttributeKindID("allockind"), allocKindAlloc|allocKindZeroed))
llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("alloc-family", "runtime.alloc"))
// Use a special value to indicate the first parameter:
// > allocsize has two integer arguments, but because they're both 32 bits, we can
// > pack them into one 64-bit value, at the cost of making said value
// > nonsensical.
// >
// > In order to do this, we need to reserve one value of the second (optional)
// > allocsize argument to signify "not present."
llvmFn.AddFunctionAttr(c.ctx.CreateEnumAttribute(llvm.AttributeKindID("allocsize"), 0x0000_0000_ffff_ffff))
}
case "runtime.sliceAppend":
// Appending a slice will only read the to-be-appended slice, it won't
// be modified.