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transform (func-lowering): remove specializations from function value lowering and fix lowering of a function value of an unimplemented type #1043

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merged 1 commit into from
Apr 12, 2020
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transform (func-lowering): remove specializations from function value lowering and fix lowering of a function value of an unimplemented type #1043

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176 changes: 82 additions & 94 deletions transform/func-lowering.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ package transform
import (
"sort"
"strconv"
"strings"

"github.com/tinygo-org/tinygo/compiler/llvmutil"
"tinygo.org/x/go-llvm"
Expand Down Expand Up @@ -55,17 +56,30 @@ func LowerFuncValues(mod llvm.Module) {
funcValueWithSignaturePtr := llvm.PointerType(mod.GetTypeByName("runtime.funcValueWithSignature"), 0)
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@aykevl aykevl Apr 12, 2020

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Sidenote: this will eventually need to be changed. I discovered that types may be renamed when LLVM modules are merged (when there are duplicates). This is a big problem in the interface lowering pass and I'm not yet sure how to fix that.

signatures := map[string]*funcSignatureInfo{}
for global := mod.FirstGlobal(); !global.IsNil(); global = llvm.NextGlobal(global) {
if global.Type() != funcValueWithSignaturePtr {
var sig, funcVal llvm.Value
switch {
case global.Type() == funcValueWithSignaturePtr:
sig = llvm.ConstExtractValue(global.Initializer(), []uint32{1})
funcVal = global
case strings.HasPrefix(global.Name(), "reflect/types.type:func:{"):
sig = global
default:
continue
}
sig := llvm.ConstExtractValue(global.Initializer(), []uint32{1})

name := sig.Name()
var funcValueWithSignatures []llvm.Value
if funcVal.IsNil() {
funcValueWithSignatures = []llvm.Value{}
} else {
funcValueWithSignatures = []llvm.Value{funcVal}
}
if info, ok := signatures[name]; ok {
info.funcValueWithSignatures = append(info.funcValueWithSignatures, global)
info.funcValueWithSignatures = append(info.funcValueWithSignatures, funcValueWithSignatures...)
} else {
signatures[name] = &funcSignatureInfo{
sig: sig,
funcValueWithSignatures: []llvm.Value{global},
funcValueWithSignatures: funcValueWithSignatures,
}
}
}
Expand Down Expand Up @@ -123,95 +137,64 @@ func LowerFuncValues(mod llvm.Module) {
panic("expected all call uses to be runtime.getFuncPtr")
}
funcID := getFuncPtrCall.Operand(1)
switch len(functions) {
case 0:
// There are no functions used in a func value that implement
// this signature. The only possible value is a nil value.
for _, inttoptr := range getUses(getFuncPtrCall) {
if inttoptr.IsAIntToPtrInst().IsNil() {
panic("expected inttoptr")
}
nilptr := llvm.ConstPointerNull(inttoptr.Type())
inttoptr.ReplaceAllUsesWith(nilptr)
inttoptr.EraseFromParentAsInstruction()

// There are functions used in a func value that
// implement this signature.
// What we'll do is transform the following:
// rawPtr := runtime.getFuncPtr(func.ptr)
// if rawPtr == nil {
// runtime.nilPanic()
// }
// result := rawPtr(...args, func.context)
// into this:
// if false {
// runtime.nilPanic()
// }
// var result // Phi
// switch fn.id {
// case 0:
// runtime.nilPanic()
// case 1:
// result = call first implementation...
// case 2:
// result = call second implementation...
// default:
// unreachable
// }

// Remove some casts, checks, and the old call which we're going
// to replace.
for _, callIntPtr := range getUses(getFuncPtrCall) {
if !callIntPtr.IsACallInst().IsNil() && callIntPtr.CalledValue().Name() == "internal/task.start" {
// Special case for goroutine starts.
addFuncLoweringSwitch(mod, builder, funcID, callIntPtr, func(funcPtr llvm.Value, params []llvm.Value) llvm.Value {
i8ptrType := llvm.PointerType(ctx.Int8Type(), 0)
calleeValue := builder.CreatePtrToInt(funcPtr, uintptrType, "")
start := mod.NamedFunction("internal/task.start")
builder.CreateCall(start, []llvm.Value{calleeValue, callIntPtr.Operand(1), llvm.Undef(i8ptrType), llvm.ConstNull(i8ptrType)}, "")
return llvm.Value{} // void so no return value
}, functions)
callIntPtr.EraseFromParentAsInstruction()
continue
}
getFuncPtrCall.EraseFromParentAsInstruction()
case 1:
// There is exactly one function with this signature that is
// used in a func value. The func value itself can be either nil
// or this one function.
builder.SetInsertPointBefore(getFuncPtrCall)
zero := llvm.ConstInt(uintptrType, 0, false)
isnil := builder.CreateICmp(llvm.IntEQ, funcID, zero, "")
funcPtrNil := llvm.ConstPointerNull(functions[0].funcPtr.Type())
funcPtr := builder.CreateSelect(isnil, funcPtrNil, functions[0].funcPtr, "")
for _, inttoptr := range getUses(getFuncPtrCall) {
if inttoptr.IsAIntToPtrInst().IsNil() {
panic("expected inttoptr")
}
inttoptr.ReplaceAllUsesWith(funcPtr)
inttoptr.EraseFromParentAsInstruction()
if callIntPtr.IsAIntToPtrInst().IsNil() {
panic("expected inttoptr")
}
getFuncPtrCall.EraseFromParentAsInstruction()
default:
// There are multiple functions used in a func value that
// implement this signature.
// What we'll do is transform the following:
// rawPtr := runtime.getFuncPtr(func.ptr)
// if rawPtr == nil {
// runtime.nilPanic()
// }
// result := rawPtr(...args, func.context)
// into this:
// if false {
// runtime.nilPanic()
// }
// var result // Phi
// switch fn.id {
// case 0:
// runtime.nilPanic()
// case 1:
// result = call first implementation...
// case 2:
// result = call second implementation...
// default:
// unreachable
// }

// Remove some casts, checks, and the old call which we're going
// to replace.
for _, callIntPtr := range getUses(getFuncPtrCall) {
if !callIntPtr.IsACallInst().IsNil() && callIntPtr.CalledValue().Name() == "internal/task.start" {
// Special case for goroutine starts.
addFuncLoweringSwitch(mod, builder, funcID, callIntPtr, func(funcPtr llvm.Value, params []llvm.Value) llvm.Value {
i8ptrType := llvm.PointerType(ctx.Int8Type(), 0)
calleeValue := builder.CreatePtrToInt(funcPtr, uintptrType, "")
start := mod.NamedFunction("internal/task.start")
builder.CreateCall(start, []llvm.Value{calleeValue, callIntPtr.Operand(1), llvm.Undef(i8ptrType), llvm.ConstNull(i8ptrType)}, "")
return llvm.Value{} // void so no return value
for _, ptrUse := range getUses(callIntPtr) {
if !ptrUse.IsAICmpInst().IsNil() {
ptrUse.ReplaceAllUsesWith(llvm.ConstInt(ctx.Int1Type(), 0, false))
} else if !ptrUse.IsACallInst().IsNil() && ptrUse.CalledValue() == callIntPtr {
addFuncLoweringSwitch(mod, builder, funcID, ptrUse, func(funcPtr llvm.Value, params []llvm.Value) llvm.Value {
return builder.CreateCall(funcPtr, params, "")
}, functions)
callIntPtr.EraseFromParentAsInstruction()
continue
}
if callIntPtr.IsAIntToPtrInst().IsNil() {
panic("expected inttoptr")
}
for _, ptrUse := range getUses(callIntPtr) {
if !ptrUse.IsAICmpInst().IsNil() {
ptrUse.ReplaceAllUsesWith(llvm.ConstInt(ctx.Int1Type(), 0, false))
} else if !ptrUse.IsACallInst().IsNil() && ptrUse.CalledValue() == callIntPtr {
addFuncLoweringSwitch(mod, builder, funcID, ptrUse, func(funcPtr llvm.Value, params []llvm.Value) llvm.Value {
return builder.CreateCall(funcPtr, params, "")
}, functions)
} else {
panic("unexpected getFuncPtrCall")
}
ptrUse.EraseFromParentAsInstruction()
} else {
panic("unexpected getFuncPtrCall")
}
callIntPtr.EraseFromParentAsInstruction()
ptrUse.EraseFromParentAsInstruction()
}
getFuncPtrCall.EraseFromParentAsInstruction()
callIntPtr.EraseFromParentAsInstruction()
}
getFuncPtrCall.EraseFromParentAsInstruction()
}
}
}
Expand Down Expand Up @@ -270,13 +253,18 @@ func addFuncLoweringSwitch(mod llvm.Module, builder llvm.Builder, funcID, call l
phiBlocks[i] = bb
phiValues[i] = result
}
// Create the PHI node so that the call result flows into the
// next block (after the split). This is only necessary when the
// call produced a value.
if call.Type().TypeKind() != llvm.VoidTypeKind {
builder.SetInsertPointBefore(nextBlock.FirstInstruction())
phi := builder.CreatePHI(call.Type(), "")
phi.AddIncoming(phiValues, phiBlocks)
call.ReplaceAllUsesWith(phi)
if len(functions) > 0 {
// Create the PHI node so that the call result flows into the
// next block (after the split). This is only necessary when the
// call produced a value.
builder.SetInsertPointBefore(nextBlock.FirstInstruction())
phi := builder.CreatePHI(call.Type(), "")
phi.AddIncoming(phiValues, phiBlocks)
call.ReplaceAllUsesWith(phi)
} else {
// This is always a nil panic, so replace the call result with undef.
call.ReplaceAllUsesWith(llvm.Undef(call.Type()))
}
}
}
24 changes: 10 additions & 14 deletions transform/testdata/func-lowering.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -4,10 +4,9 @@ target triple = "wasm32-unknown-unknown-wasm"
%runtime.typecodeID = type { %runtime.typecodeID*, i32 }
%runtime.funcValueWithSignature = type { i32, %runtime.typecodeID* }

@"reflect/types.type:func:{basic:int8}{}" = external constant %runtime.typecodeID
@"reflect/types.type:func:{basic:uint8}{}" = external constant %runtime.typecodeID
@"reflect/types.type:func:{basic:int}{}" = external constant %runtime.typecodeID
@"funcInt8$withSignature" = constant %runtime.funcValueWithSignature { i32 ptrtoint (void (i8, i8*, i8*)* @funcInt8 to i32), %runtime.typecodeID* @"reflect/types.type:func:{basic:int8}{}" }
@"reflect/types.type:func:{}{basic:uint32}" = external constant %runtime.typecodeID
@"func1Uint8$withSignature" = constant %runtime.funcValueWithSignature { i32 ptrtoint (void (i8, i8*, i8*)* @func1Uint8 to i32), %runtime.typecodeID* @"reflect/types.type:func:{basic:uint8}{}" }
@"func2Uint8$withSignature" = constant %runtime.funcValueWithSignature { i32 ptrtoint (void (i8, i8*, i8*)* @func2Uint8 to i32), %runtime.typecodeID* @"reflect/types.type:func:{basic:uint8}{}" }
@"main$withSignature" = constant %runtime.funcValueWithSignature { i32 ptrtoint (void (i32, i8*, i8*)* @"main$1" to i32), %runtime.typecodeID* @"reflect/types.type:func:{basic:int}{}" }
Expand All @@ -23,29 +22,26 @@ declare void @"main$1"(i32, i8*, i8*)

declare void @"main$2"(i32, i8*, i8*)

declare void @funcInt8(i8, i8*, i8*)

declare void @func1Uint8(i8, i8*, i8*)

declare void @func2Uint8(i8, i8*, i8*)

; Call a function of which only one function with this signature is used as a
; function value. This means that lowering it to IR is trivial: simply check
; whether the func value is nil, and if not, call that one function directly.
define void @runFunc1(i8*, i32, i8, i8* %context, i8* %parentHandle) {
; There are no functions with this signature used in a func value.
; This means that this should unconditionally nil panic.
define i32 @runFuncNone(i8*, i32, i8* %context, i8* %parentHandle) {
entry:
%3 = call i32 @runtime.getFuncPtr(i8* %0, i32 %1, %runtime.typecodeID* @"reflect/types.type:func:{basic:int8}{}", i8* undef, i8* null)
%4 = inttoptr i32 %3 to void (i8, i8*, i8*)*
%5 = icmp eq void (i8, i8*, i8*)* %4, null
br i1 %5, label %fpcall.nil, label %fpcall.next
%2 = call i32 @runtime.getFuncPtr(i8* %0, i32 %1, %runtime.typecodeID* @"reflect/types.type:func:{}{basic:uint32}", i8* undef, i8* null)
%3 = inttoptr i32 %2 to i32 (i8*, i8*)*
%4 = icmp eq i32 (i8*, i8*)* %3, null
br i1 %4, label %fpcall.nil, label %fpcall.next

fpcall.nil:
call void @runtime.nilPanic(i8* undef, i8* null)
unreachable

fpcall.next:
call void %4(i8 %2, i8* %0, i8* undef)
ret void
%5 = call i32 %3(i8* %0, i8* undef)
ret i32 %5
}

; There are two functions with this signature used in a func value. That means
Expand Down
27 changes: 16 additions & 11 deletions transform/testdata/func-lowering.out.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -4,10 +4,9 @@ target triple = "wasm32-unknown-unknown-wasm"
%runtime.typecodeID = type { %runtime.typecodeID*, i32 }
%runtime.funcValueWithSignature = type { i32, %runtime.typecodeID* }

@"reflect/types.type:func:{basic:int8}{}" = external constant %runtime.typecodeID
@"reflect/types.type:func:{basic:uint8}{}" = external constant %runtime.typecodeID
@"reflect/types.type:func:{basic:int}{}" = external constant %runtime.typecodeID
@"funcInt8$withSignature" = constant %runtime.funcValueWithSignature { i32 ptrtoint (void (i8, i8*, i8*)* @funcInt8 to i32), %runtime.typecodeID* @"reflect/types.type:func:{basic:int8}{}" }
@"reflect/types.type:func:{}{basic:uint32}" = external constant %runtime.typecodeID
@"func1Uint8$withSignature" = constant %runtime.funcValueWithSignature { i32 ptrtoint (void (i8, i8*, i8*)* @func1Uint8 to i32), %runtime.typecodeID* @"reflect/types.type:func:{basic:uint8}{}" }
@"func2Uint8$withSignature" = constant %runtime.funcValueWithSignature { i32 ptrtoint (void (i8, i8*, i8*)* @func2Uint8 to i32), %runtime.typecodeID* @"reflect/types.type:func:{basic:uint8}{}" }
@"main$withSignature" = constant %runtime.funcValueWithSignature { i32 ptrtoint (void (i32, i8*, i8*)* @"main$1" to i32), %runtime.typecodeID* @"reflect/types.type:func:{basic:int}{}" }
Expand All @@ -23,26 +22,32 @@ declare void @"main$1"(i32, i8*, i8*)

declare void @"main$2"(i32, i8*, i8*)

declare void @funcInt8(i8, i8*, i8*)

declare void @func1Uint8(i8, i8*, i8*)

declare void @func2Uint8(i8, i8*, i8*)

define void @runFunc1(i8* %0, i32 %1, i8 %2, i8* %context, i8* %parentHandle) {
define i32 @runFuncNone(i8* %0, i32 %1, i8* %context, i8* %parentHandle) {
entry:
%3 = icmp eq i32 %1, 0
%4 = select i1 %3, void (i8, i8*, i8*)* null, void (i8, i8*, i8*)* @funcInt8
%5 = icmp eq void (i8, i8*, i8*)* %4, null
br i1 %5, label %fpcall.nil, label %fpcall.next
br i1 false, label %fpcall.nil, label %fpcall.next

fpcall.nil: ; preds = %entry
call void @runtime.nilPanic(i8* undef, i8* null)
unreachable

fpcall.next: ; preds = %entry
call void %4(i8 %2, i8* %0, i8* undef)
ret void
switch i32 %1, label %func.default [
i32 0, label %func.nil
]

func.nil: ; preds = %fpcall.next
call void @runtime.nilPanic(i8* undef, i8* null)
unreachable

func.next: ; No predecessors!
ret i32 undef

func.default: ; preds = %fpcall.next
unreachable
}

define void @runFunc2(i8* %0, i32 %1, i8 %2, i8* %context, i8* %parentHandle) {
Expand Down