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cmd/gc: evaluate concrete == interface without allocating
Consider an interface value i of type I and concrete value c of type C. Prior to this CL, i==c was evaluated as I(c) == i Evaluating I(c) can allocate. This CL changes the evaluation of i==c to x, ok := i.(C); ok && x == c The new generated code is shorter and does not allocate directly. If C is small, as it is in every instance in the stdlib, the new code also uses less stack space and makes one runtime call instead of two. If C is very large, the original implementation is used. The cutoff for "very large" is 1<<16, following the stack vs heap cutoff used elsewhere. This kind of comparison occurs in 38 places in the stdlib, mostly in the net and os packages. benchmark old ns/op new ns/op delta BenchmarkEqEfaceConcrete 29.5 7.92 -73.15% BenchmarkEqIfaceConcrete 32.1 7.90 -75.39% BenchmarkNeEfaceConcrete 29.9 7.90 -73.58% BenchmarkNeIfaceConcrete 35.9 7.90 -77.99% Fixes #9370. Change-Id: I7c4555950bcd6406ee5c613be1f2128da2c9a2b7 Reviewed-on: https://go-review.googlesource.com/2096 Reviewed-by: Russ Cox <rsc@golang.org> Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
This commit is contained in:
Josh Bleecher Snyder
parent
747c849833
commit
77a2113925
@ -570,6 +570,7 @@ reswitch:
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et = t->etype;
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if(et == TIDEAL)
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et = TINT;
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aop = 0;
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if(iscmp[n->op] && t->etype != TIDEAL && !eqtype(l->type, r->type)) {
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// comparison is okay as long as one side is
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// assignable to the other. convert so they have
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@ -577,16 +578,20 @@ reswitch:
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//
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// the only conversion that isn't a no-op is concrete == interface.
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// in that case, check comparability of the concrete type.
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// The conversion allocates, so only do it if the concrete type is huge.
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if(r->type->etype != TBLANK && (aop = assignop(l->type, r->type, nil)) != 0) {
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if(isinter(r->type) && !isinter(l->type) && algtype1(l->type, nil) == ANOEQ) {
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yyerror("invalid operation: %N (operator %O not defined on %s)", n, op, typekind(l->type));
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goto error;
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}
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l = nod(aop, l, N);
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l->type = r->type;
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l->typecheck = 1;
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n->left = l;
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t = l->type;
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dowidth(l->type);
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if(isinter(r->type) == isinter(l->type) || l->type->width >= 1<<16) {
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l = nod(aop, l, N);
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l->type = r->type;
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l->typecheck = 1;
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n->left = l;
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}
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t = r->type;
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goto converted;
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}
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if(l->type->etype != TBLANK && (aop = assignop(r->type, l->type, nil)) != 0) {
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@ -594,11 +599,14 @@ reswitch:
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yyerror("invalid operation: %N (operator %O not defined on %s)", n, op, typekind(r->type));
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goto error;
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}
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r = nod(aop, r, N);
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r->type = l->type;
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r->typecheck = 1;
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n->right = r;
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t = r->type;
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dowidth(r->type);
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if(isinter(r->type) == isinter(l->type) || r->type->width >= 1<<16) {
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r = nod(aop, r, N);
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r->type = l->type;
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r->typecheck = 1;
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n->right = r;
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}
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t = l->type;
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}
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converted:
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et = t->etype;
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@ -609,8 +617,10 @@ reswitch:
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yyerror("invalid operation: %N (non-numeric type %T)", n, l->type);
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goto error;
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}
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yyerror("invalid operation: %N (mismatched types %T and %T)", n, l->type, r->type);
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goto error;
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if(isinter(r->type) == isinter(l->type) || aop == 0) {
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yyerror("invalid operation: %N (mismatched types %T and %T)", n, l->type, r->type);
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goto error;
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}
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}
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if(!okfor[op][et]) {
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yyerror("invalid operation: %N (operator %O not defined on %s)", n, op, typekind(t));
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@ -685,7 +695,7 @@ reswitch:
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n->right = l;
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} else if(r->op == OLITERAL && r->val.ctype == CTNIL) {
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// leave alone for back end
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} else {
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} else if(isinter(r->type) == isinter(l->type)) {
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n->etype = n->op;
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n->op = OCMPIFACE;
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}
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@ -3339,10 +3339,51 @@ static void
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walkcompare(Node **np, NodeList **init)
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{
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Node *n, *l, *r, *call, *a, *li, *ri, *expr, *cmpl, *cmpr;
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Node *x, *ok;
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int andor, i, needsize;
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Type *t, *t1;
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n = *np;
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// Given interface value l and concrete value r, rewrite
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// l == r
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// to
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// x, ok := l.(type(r)); ok && x == r
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// Handle != similarly.
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// This avoids the allocation that would be required
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// to convert r to l for comparison.
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l = N;
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r = N;
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if(isinter(n->left->type) && !isinter(n->right->type)) {
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l = n->left;
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r = n->right;
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} else if(!isinter(n->left->type) && isinter(n->right->type)) {
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l = n->right;
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r = n->left;
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}
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if(l != N) {
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x = temp(r->type);
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ok = temp(types[TBOOL]);
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// l.(type(r))
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a = nod(ODOTTYPE, l, N);
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a->type = r->type;
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// x, ok := l.(type(r))
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expr = nod(OAS2, N, N);
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expr->list = list1(x);
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expr->list = list(expr->list, ok);
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expr->rlist = list1(a);
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typecheck(&expr, Etop);
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walkexpr(&expr, init);
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if(n->op == OEQ)
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r = nod(OANDAND, ok, nod(OEQ, x, r));
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else
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r = nod(OOROR, nod(ONOT, ok, N), nod(ONE, x, r));
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*init = list(*init, expr);
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goto ret;
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}
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// Must be comparison of array or struct.
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// Otherwise back end handles it.
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@ -5,6 +5,7 @@
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package runtime_test
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import (
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"runtime"
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"testing"
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)
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@ -38,6 +39,47 @@ var (
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tl TL
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)
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// Issue 9370
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func TestCmpIfaceConcreteAlloc(t *testing.T) {
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if runtime.Compiler != "gc" {
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t.Skip("skipping on non-gc compiler")
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}
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n := testing.AllocsPerRun(1, func() {
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_ = e == ts
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_ = i1 == ts
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_ = e == 1
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})
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if n > 0 {
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t.Fatalf("iface cmp allocs=%v; want 0", n)
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}
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}
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func BenchmarkEqEfaceConcrete(b *testing.B) {
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for i := 0; i < b.N; i++ {
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_ = e == ts
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}
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}
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func BenchmarkEqIfaceConcrete(b *testing.B) {
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for i := 0; i < b.N; i++ {
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_ = i1 == ts
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}
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}
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func BenchmarkNeEfaceConcrete(b *testing.B) {
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for i := 0; i < b.N; i++ {
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_ = e != ts
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}
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}
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func BenchmarkNeIfaceConcrete(b *testing.B) {
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for i := 0; i < b.N; i++ {
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_ = i1 != ts
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}
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}
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func BenchmarkConvT2ESmall(b *testing.B) {
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for i := 0; i < b.N; i++ {
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e = ts
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127
test/fixedbugs/issue9370.go
Normal file
127
test/fixedbugs/issue9370.go
Normal file
@ -0,0 +1,127 @@
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// errorcheck
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// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Verify that concrete/interface comparisons are
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// typechecked correctly by the compiler.
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package main
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type I interface {
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Method()
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}
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type C int
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func (C) Method() {}
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type G func()
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func (G) Method() {}
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var (
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e interface{}
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i I
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c C
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n int
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f func()
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g G
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)
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var (
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_ = e == c
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_ = e != c
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_ = e >= c // ERROR "invalid operation.*not defined"
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_ = c == e
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_ = c != e
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_ = c >= e // ERROR "invalid operation.*not defined"
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_ = i == c
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_ = i != c
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_ = i >= c // ERROR "invalid operation.*not defined"
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_ = c == i
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_ = c != i
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_ = c >= i // ERROR "invalid operation.*not defined"
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_ = e == n
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_ = e != n
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_ = e >= n // ERROR "invalid operation.*not defined"
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_ = n == e
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_ = n != e
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_ = n >= e // ERROR "invalid operation.*not defined"
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// i and n are not assignable to each other
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_ = i == n // ERROR "invalid operation.*mismatched types"
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_ = i != n // ERROR "invalid operation.*mismatched types"
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_ = i >= n // ERROR "invalid operation.*mismatched types"
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_ = n == i // ERROR "invalid operation.*mismatched types"
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_ = n != i // ERROR "invalid operation.*mismatched types"
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_ = n >= i // ERROR "invalid operation.*mismatched types"
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_ = e == 1
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_ = e != 1
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_ = e >= 1 // ERROR "invalid operation.*not defined"
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_ = 1 == e
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_ = 1 != e
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_ = 1 >= e // ERROR "invalid operation.*not defined"
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_ = i == 1 // ERROR "invalid operation.*mismatched types"
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_ = i != 1 // ERROR "invalid operation.*mismatched types"
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_ = i >= 1 // ERROR "invalid operation.*mismatched types"
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_ = 1 == i // ERROR "invalid operation.*mismatched types"
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_ = 1 != i // ERROR "invalid operation.*mismatched types"
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_ = 1 >= i // ERROR "invalid operation.*mismatched types"
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_ = e == f // ERROR "invalid operation.*not defined"
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_ = e != f // ERROR "invalid operation.*not defined"
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_ = e >= f // ERROR "invalid operation.*not defined"
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_ = f == e // ERROR "invalid operation.*not defined"
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_ = f != e // ERROR "invalid operation.*not defined"
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_ = f >= e // ERROR "invalid operation.*not defined"
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_ = i == f // ERROR "invalid operation.*mismatched types"
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_ = i != f // ERROR "invalid operation.*mismatched types"
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_ = i >= f // ERROR "invalid operation.*mismatched types"
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_ = f == i // ERROR "invalid operation.*mismatched types"
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_ = f != i // ERROR "invalid operation.*mismatched types"
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_ = f >= i // ERROR "invalid operation.*mismatched types"
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_ = e == g // ERROR "invalid operation.*not defined"
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_ = e != g // ERROR "invalid operation.*not defined"
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_ = e >= g // ERROR "invalid operation.*not defined"
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_ = g == e // ERROR "invalid operation.*not defined"
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_ = g != e // ERROR "invalid operation.*not defined"
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_ = g >= e // ERROR "invalid operation.*not defined"
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_ = i == g // ERROR "invalid operation.*not defined"
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_ = i != g // ERROR "invalid operation.*not defined"
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_ = i >= g // ERROR "invalid operation.*not defined"
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_ = g == i // ERROR "invalid operation.*not defined"
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_ = g != i // ERROR "invalid operation.*not defined"
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_ = g >= i // ERROR "invalid operation.*not defined"
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_ = _ == e // ERROR "cannot use _ as value"
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_ = _ == i // ERROR "cannot use _ as value"
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_ = _ == c // ERROR "cannot use _ as value"
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_ = _ == n // ERROR "cannot use _ as value"
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_ = _ == f // ERROR "cannot use _ as value"
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_ = _ == g // ERROR "cannot use _ as value"
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_ = e == _ // ERROR "cannot use _ as value"
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_ = i == _ // ERROR "cannot use _ as value"
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_ = c == _ // ERROR "cannot use _ as value"
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_ = n == _ // ERROR "cannot use _ as value"
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_ = f == _ // ERROR "cannot use _ as value"
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_ = g == _ // ERROR "cannot use _ as value"
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_ = _ == _ // ERROR "cannot use _ as value"
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_ = e ^ c // ERROR "invalid operation.*mismatched types"
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_ = c ^ e // ERROR "invalid operation.*mismatched types"
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_ = 1 ^ e // ERROR "invalid operation.*mismatched types"
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_ = e ^ 1 // ERROR "invalid operation.*mismatched types"
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_ = 1 ^ c
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_ = c ^ 1
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)
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@ -137,10 +137,7 @@ var i9 interface{}
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func f9() bool {
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g8()
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x := i9
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// using complex number in comparison so that
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// there is always a convT2E, no matter what the
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// interface rules are.
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return x != 99.0i // ERROR "live at call to convT2E: x"
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return x != interface{}(99.0i) // ERROR "live at call to convT2E: x"
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}
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// liveness formerly confused by UNDEF followed by RET,
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