Method createRuntimeAssert

compiler/asserts.go:233–260

createRuntimeAssert is a common function to create a new branch on an assert bool, calling an assert func if the assert value is true (1).

(assert llvm.Value, blockPrefix, assertFunc string)

// createRuntimeAssert is a common function to create a new branch on an assert
// bool, calling an assert func if the assert value is true (1).
func (b *builder) createRuntimeAssert(assert llvm.Value, blockPrefix, assertFunc string) {
	// Check whether we can resolve this check at compile time.
	if !assert.IsAConstantInt().IsNil() {
		val := assert.ZExtValue()
		if val == 0 {
			// Everything is constant so the check does not have to be emitted
			// in IR. This avoids emitting some redundant IR.
			return
		}
	}

	// Put the fault block at the end of the function and the next block at the
	// current insert position.
	faultBlock := b.ctx.AddBasicBlock(b.llvmFn, blockPrefix+".throw")
	nextBlock := b.insertBasicBlock(blockPrefix + ".next")
	b.currentBlockInfo.exit = nextBlock // adjust outgoing block for phi nodes

	// Now branch to the out-of-bounds or the regular block.
	b.CreateCondBr(assert, faultBlock, nextBlock)

	// Fail: the assert triggered so panic.
	b.SetInsertPointAtEnd(faultBlock)
	b.createRuntimeCall(assertFunc, nil, "")
	b.CreateUnreachable()

	// Ok: assert didn't trigger so continue normally.
	b.SetInsertPointAtEnd(nextBlock)
}

// extendInteger extends the value to at least targetType using a zero or sign
// extend. The resulting value is not truncated: it may still be bigger than