622d0ebde6
This commit implements nil checks for all platforms. These nil checks
can be optimized on systems with a MMU, but since a major target is
systems without MMU, keep it this way for now.
It implements three checks:
* Nil checks before dereferencing a pointer.
* Nil checks before calculating an address (*ssa.FieldAddr and
*ssa.IndexAddr)
* Nil checks before calling a function pointer.
The first check has by far the biggest impact, with around 5% increase
in code size. The other checks only trigger in only some test cases and
have a minimal impact on code size.
This first nil check is also the one that is easiest to avoid on systems
with MMU, if necessary.
31 строка
1,1 КиБ
Go
31 строка
1,1 КиБ
Go
package compiler
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// This file implements functions that do certain safety checks that are
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// required by the Go programming language.
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import (
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"tinygo.org/x/go-llvm"
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)
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// emitNilCheck checks whether the given pointer is nil, and panics if it is. It
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// has no effect in well-behaved programs, but makes sure no uncaught nil
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// pointer dereferences exist in valid Go code.
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func (c *Compiler) emitNilCheck(frame *Frame, ptr llvm.Value, blockPrefix string) {
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// Check whether this is a nil pointer.
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faultBlock := c.ctx.AddBasicBlock(frame.fn.LLVMFn, blockPrefix+".nil")
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nextBlock := c.ctx.AddBasicBlock(frame.fn.LLVMFn, blockPrefix+".next")
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frame.blockExits[frame.currentBlock] = nextBlock // adjust outgoing block for phi nodes
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// Compare against nil.
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nilptr := llvm.ConstPointerNull(ptr.Type())
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isnil := c.builder.CreateICmp(llvm.IntEQ, ptr, nilptr, "")
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c.builder.CreateCondBr(isnil, faultBlock, nextBlock)
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// Fail: this is a nil pointer, exit with a panic.
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c.builder.SetInsertPointAtEnd(faultBlock)
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c.createRuntimeCall("nilpanic", nil, "")
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c.builder.CreateUnreachable()
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// Ok: this is a valid pointer.
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c.builder.SetInsertPointAtEnd(nextBlock)
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}
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