From f5184d34376f92bfa99ec5ca343fe425fd98be85 Mon Sep 17 00:00:00 2001 From: Russ Cox Date: Thu, 15 May 2014 15:34:53 -0400 Subject: [PATCH] cmd/gc: correct handling of globals, func args, results Globals, function arguments, and results are special cases in registerization. Globals must be flushed aggressively, because nearly any operation can cause a panic, and the recovery code must see the latest values. Globals also must be loaded aggressively, because nearly any store through a pointer might be updating a global: the compiler cannot see all the "address of" operations on globals, especially exported globals. To accomplish this, mark all globals as having their address taken, which effectively disables registerization. If a function contains a defer statement, the function results must be flushed aggressively, because nearly any operation can cause a panic, and the deferred code may call recover, causing the original function to return the current values of its function results. To accomplish this, mark all function results as having their address taken if the function contains any defer statements. This causes not just aggressive flushing but also aggressive loading. The aggressive loading is overkill but the best we can do in the current code. Function arguments must be considered live at all safe points in a function, because garbage collection always preserves them: they must be up-to-date in order to be preserved correctly. Accomplish this by marking them live at all call sites. An earlier attempt at this marked function arguments as having their address taken, which disabled registerization completely, making programs slower. This CL's solution allows registerization while preserving safety. The benchmark speedup is caused by being able to registerize again (the earlier CL lost the same amount). benchmark old ns/op new ns/op delta BenchmarkEqualPort32 61.4 56.0 -8.79% benchmark old MB/s new MB/s speedup BenchmarkEqualPort32 521.56 570.97 1.09x Fixes #1304. (again) Fixes #7944. (again) Fixes #7984. Fixes #7995. LGTM=khr R=golang-codereviews, khr CC=golang-codereviews, iant, r https://golang.org/cl/97500044 --- src/cmd/5g/reg.c | 64 ++++++----------- src/cmd/6g/reg.c | 67 +++++++----------- src/cmd/8g/reg.c | 66 +++++++----------- test/fixedbugs/issue1304.go | 23 +++++++ test/fixedbugs/issue7995.go | 25 +++++++ test/fixedbugs/issue7995b.dir/x1.go | 16 +++++ test/fixedbugs/issue7995b.dir/x2.go | 10 +++ test/fixedbugs/issue7995b.go | 9 +++ test/nilptr3.go | 102 ++++++++++++++-------------- 9 files changed, 202 insertions(+), 180 deletions(-) create mode 100644 test/fixedbugs/issue1304.go create mode 100644 test/fixedbugs/issue7995.go create mode 100644 test/fixedbugs/issue7995b.dir/x1.go create mode 100644 test/fixedbugs/issue7995b.dir/x2.go create mode 100644 test/fixedbugs/issue7995b.go diff --git a/src/cmd/5g/reg.c b/src/cmd/5g/reg.c index 3eadde4cf4..6129698f3a 100644 --- a/src/cmd/5g/reg.c +++ b/src/cmd/5g/reg.c @@ -56,28 +56,6 @@ rcmp(const void *a1, const void *a2) return p2->varno - p1->varno; } -static void -setvar(Bits *dst, Type **args) -{ - Type *t; - Node *n; - Addr a; - Iter save; - Bits bit; - int z; - - t = structfirst(&save, args); - while(t != T) { - n = nodarg(t, 1); - a = zprog.from; - naddr(n, &a, 0); - bit = mkvar(R, &a); - for(z=0; zb[z] |= bit.b[z]; - t = structnext(&save); - } -} - void excise(Flow *r) { @@ -192,11 +170,6 @@ regopt(Prog *firstp) ovar.b[z] = 0; } - // build lists of parameters and results - setvar(&ivar, getthis(curfn->type)); - setvar(&ivar, getinarg(curfn->type)); - setvar(&ovar, getoutarg(curfn->type)); - /* * pass 1 * build aux data structure @@ -837,9 +810,6 @@ mkvar(Reg *r, Adr *a) v->nextinnode = node->opt; node->opt = v; - if(debug['R']) - print("bit=%2d et=%2E w=%d+%d %#N %D flag=%d\n", i, et, o, w, node, a, v->addr); - bit = blsh(i); if(n == D_EXTERN || n == D_STATIC) for(z=0; zclass == PPARAM) + for(z=0; zclass == PPARAMOUT) + for(z=0; zaddrtaken) - setaddrs(bit); + v->addr = 1; + + // Disable registerization for globals, because: + // (1) we might panic at any time and we want the recovery code + // to see the latest values (issue 1304). + // (2) we don't know what pointers might point at them and we want + // loads via those pointers to see updated values and vice versa (issue 7995). + // + // Disable registerization for results if using defer, because the deferred func + // might recover and return, causing the current values to be used. + if(node->class == PEXTERN || (hasdefer && node->class == PPARAMOUT)) + v->addr = 1; + + if(debug['R']) + print("bit=%2d et=%2E w=%d+%d %#N %D flag=%d\n", i, et, o, w, node, a, v->addr); return bit; @@ -961,17 +952,6 @@ prop(Reg *r, Bits ref, Bits cal) ref.b[z] = 0; } break; - - default: - // Work around for issue 1304: - // flush modified globals before each instruction. - for(z=0; zset.b[z]) | diff --git a/src/cmd/6g/reg.c b/src/cmd/6g/reg.c index a1f0c756aa..919a07d7bc 100644 --- a/src/cmd/6g/reg.c +++ b/src/cmd/6g/reg.c @@ -54,28 +54,6 @@ rcmp(const void *a1, const void *a2) return p2->varno - p1->varno; } -static void -setvar(Bits *dst, Type **args) -{ - Type *t; - Node *n; - Addr a; - Iter save; - Bits bit; - int z; - - t = structfirst(&save, args); - while(t != T) { - n = nodarg(t, 1); - a = zprog.from; - naddr(n, &a, 0); - bit = mkvar(R, &a); - for(z=0; zb[z] |= bit.b[z]; - t = structnext(&save); - } -} - static void setaddrs(Bits bit) { @@ -178,11 +156,6 @@ regopt(Prog *firstp) ovar.b[z] = 0; } - // build lists of parameters and results - setvar(&ivar, getthis(curfn->type)); - setvar(&ivar, getinarg(curfn->type)); - setvar(&ovar, getoutarg(curfn->type)); - /* * pass 1 * build aux data structure @@ -690,11 +663,6 @@ mkvar(Reg *r, Adr *a) v->nextinnode = node->opt; node->opt = v; - if(debug['R']) - print("bit=%2d et=%2E w=%lld+%lld %#N %D flag=%d\n", i, et, o, w, node, a, v->addr); - - ostats.nvar++; - bit = blsh(i); if(n == D_EXTERN || n == D_STATIC) for(z=0; zclass == PPARAM) + for(z=0; zclass == PPARAMOUT) + for(z=0; zaddrtaken) - setaddrs(bit); + v->addr = 1; + + // Disable registerization for globals, because: + // (1) we might panic at any time and we want the recovery code + // to see the latest values (issue 1304). + // (2) we don't know what pointers might point at them and we want + // loads via those pointers to see updated values and vice versa (issue 7995). + // + // Disable registerization for results if using defer, because the deferred func + // might recover and return, causing the current values to be used. + if(node->class == PEXTERN || (hasdefer && node->class == PPARAMOUT)) + v->addr = 1; + + if(debug['R']) + print("bit=%2d et=%2E w=%lld+%lld %#N %D flag=%d\n", i, et, o, w, node, a, v->addr); + ostats.nvar++; return bit; @@ -816,17 +806,6 @@ prop(Reg *r, Bits ref, Bits cal) ref.b[z] = 0; } break; - - default: - // Work around for issue 1304: - // flush modified globals before each instruction. - for(z=0; zset.b[z]) | diff --git a/src/cmd/8g/reg.c b/src/cmd/8g/reg.c index 046011c905..ed019f9373 100644 --- a/src/cmd/8g/reg.c +++ b/src/cmd/8g/reg.c @@ -54,28 +54,6 @@ rcmp(const void *a1, const void *a2) return p2->varno - p1->varno; } -static void -setvar(Bits *dst, Type **args) -{ - Type *t; - Node *n; - Addr a; - Iter save; - Bits bit; - int z; - - t = structfirst(&save, args); - while(t != T) { - n = nodarg(t, 1); - a = zprog.from; - naddr(n, &a, 0); - bit = mkvar(R, &a); - for(z=0; zb[z] |= bit.b[z]; - t = structnext(&save); - } -} - static void setaddrs(Bits bit) { @@ -148,11 +126,6 @@ regopt(Prog *firstp) ovar.b[z] = 0; } - // build lists of parameters and results - setvar(&ivar, getthis(curfn->type)); - setvar(&ivar, getinarg(curfn->type)); - setvar(&ovar, getoutarg(curfn->type)); - /* * pass 1 * build aux data structure @@ -656,10 +629,6 @@ mkvar(Reg *r, Adr *a) v->nextinnode = node->opt; node->opt = v; - if(debug['R']) - print("bit=%2d et=%2E w=%d+%d %#N %D flag=%d\n", i, et, o, w, node, a, v->addr); - ostats.nvar++; - bit = blsh(i); if(n == D_EXTERN || n == D_STATIC) for(z=0; zclass == PPARAM) + for(z=0; zclass == PPARAMOUT) + for(z=0; zaddrtaken) - setaddrs(bit); + v->addr = 1; + + // Disable registerization for globals, because: + // (1) we might panic at any time and we want the recovery code + // to see the latest values (issue 1304). + // (2) we don't know what pointers might point at them and we want + // loads via those pointers to see updated values and vice versa (issue 7995). + // + // Disable registerization for results if using defer, because the deferred func + // might recover and return, causing the current values to be used. + if(node->class == PEXTERN || (hasdefer && node->class == PPARAMOUT)) + v->addr = 1; + + if(debug['R']) + print("bit=%2d et=%2E w=%d+%d %#N %D flag=%d\n", i, et, o, w, node, a, v->addr); + ostats.nvar++; return bit; @@ -781,17 +772,6 @@ prop(Reg *r, Bits ref, Bits cal) ref.b[z] = 0; } break; - - default: - // Work around for issue 1304: - // flush modified globals before each instruction. - for(z=0; zset.b[z]) | diff --git a/test/fixedbugs/issue1304.go b/test/fixedbugs/issue1304.go new file mode 100644 index 0000000000..1206e1840f --- /dev/null +++ b/test/fixedbugs/issue1304.go @@ -0,0 +1,23 @@ +// run + +// Copyright 2014 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package main + +var a = 1 + +func main() { + defer func() { + recover() + if a != 2 { + println("BUG a =", a) + } + }() + a = 2 + b := a - a + c := 4 + a = c / b + a = 3 +} diff --git a/test/fixedbugs/issue7995.go b/test/fixedbugs/issue7995.go new file mode 100644 index 0000000000..05f116823f --- /dev/null +++ b/test/fixedbugs/issue7995.go @@ -0,0 +1,25 @@ +// run + +// Copyright 2014 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Issue 7995: globals not flushed quickly enough. + +package main + +import "fmt" + +var ( + p = 1 + q = &p +) + +func main() { + p = 50 + *q = 100 + s := fmt.Sprintln(p, *q) + if s != "100 100\n" { + println("BUG:", s) + } +} diff --git a/test/fixedbugs/issue7995b.dir/x1.go b/test/fixedbugs/issue7995b.dir/x1.go new file mode 100644 index 0000000000..075911b921 --- /dev/null +++ b/test/fixedbugs/issue7995b.dir/x1.go @@ -0,0 +1,16 @@ +package x1 + +import "fmt" + +var P int + +var b bool + +func F(x *int) string { + if b { // avoid inlining + F(x) + } + P = 50 + *x = 100 + return fmt.Sprintln(P, *x) +} diff --git a/test/fixedbugs/issue7995b.dir/x2.go b/test/fixedbugs/issue7995b.dir/x2.go new file mode 100644 index 0000000000..eea23eabba --- /dev/null +++ b/test/fixedbugs/issue7995b.dir/x2.go @@ -0,0 +1,10 @@ +package main + +import "./x1" + +func main() { + s := x1.F(&x1.P) + if s != "100 100\n" { + println("BUG:", s) + } +} diff --git a/test/fixedbugs/issue7995b.go b/test/fixedbugs/issue7995b.go new file mode 100644 index 0000000000..2f57371e37 --- /dev/null +++ b/test/fixedbugs/issue7995b.go @@ -0,0 +1,9 @@ +// rundir + +// Copyright 2014 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Issue 7995: globals not flushed quickly enough. + +package ignored diff --git a/test/nilptr3.go b/test/nilptr3.go index 08597a02d9..2757daef0b 100644 --- a/test/nilptr3.go +++ b/test/nilptr3.go @@ -17,7 +17,7 @@ type Struct struct { type BigStruct struct { X int Y float64 - A [1<<20]int + A [1 << 20]int Z string } @@ -29,93 +29,94 @@ type Empty1 struct { } var ( - intp *int - arrayp *[10]int - array0p *[0]int - bigarrayp *[1<<26]int - structp *Struct + intp *int + arrayp *[10]int + array0p *[0]int + bigarrayp *[1 << 26]int + structp *Struct bigstructp *BigStruct - emptyp *Empty - empty1p *Empty1 + emptyp *Empty + empty1p *Empty1 ) func f1() { _ = *intp // ERROR "generated nil check" - + // This one should be removed but the block copy needs // to be turned into its own pseudo-op in order to see // the indirect. _ = *arrayp // ERROR "generated nil check" - - // 0-byte indirect doesn't suffice + + // 0-byte indirect doesn't suffice. + // we don't registerize globals, so there are no removed repeated nil checks. + _ = *array0p // ERROR "generated nil check" _ = *array0p // ERROR "generated nil check" - _ = *array0p // ERROR "removed repeated nil check" 386 - _ = *intp // ERROR "removed repeated nil check" - _ = *arrayp // ERROR "removed repeated nil check" + _ = *intp // ERROR "generated nil check" + _ = *arrayp // ERROR "generated nil check" _ = *structp // ERROR "generated nil check" - _ = *emptyp // ERROR "generated nil check" - _ = *arrayp // ERROR "removed repeated nil check" + _ = *emptyp // ERROR "generated nil check" + _ = *arrayp // ERROR "generated nil check" } func f2() { var ( - intp *int - arrayp *[10]int - array0p *[0]int - bigarrayp *[1<<20]int - structp *Struct + intp *int + arrayp *[10]int + array0p *[0]int + bigarrayp *[1 << 20]int + structp *Struct bigstructp *BigStruct - emptyp *Empty - empty1p *Empty1 + emptyp *Empty + empty1p *Empty1 ) - _ = *intp // ERROR "generated nil check" - _ = *arrayp // ERROR "generated nil check" - _ = *array0p // ERROR "generated nil check" - _ = *array0p // ERROR "removed repeated nil check" - _ = *intp // ERROR "removed repeated nil check" - _ = *arrayp // ERROR "removed repeated nil check" - _ = *structp // ERROR "generated nil check" - _ = *emptyp // ERROR "generated nil check" - _ = *arrayp // ERROR "removed repeated nil check" - _ = *bigarrayp // ERROR "generated nil check" ARM removed nil check before indirect!! + _ = *intp // ERROR "generated nil check" + _ = *arrayp // ERROR "generated nil check" + _ = *array0p // ERROR "generated nil check" + _ = *array0p // ERROR "removed repeated nil check" + _ = *intp // ERROR "removed repeated nil check" + _ = *arrayp // ERROR "removed repeated nil check" + _ = *structp // ERROR "generated nil check" + _ = *emptyp // ERROR "generated nil check" + _ = *arrayp // ERROR "removed repeated nil check" + _ = *bigarrayp // ERROR "generated nil check" ARM removed nil check before indirect!! _ = *bigstructp // ERROR "generated nil check" - _ = *empty1p // ERROR "generated nil check" + _ = *empty1p // ERROR "generated nil check" } func fx10k() *[10000]int -var b bool +var b bool func f3(x *[10000]int) { // Using a huge type and huge offsets so the compiler // does not expect the memory hardware to fault. _ = x[9999] // ERROR "generated nil check" - + for { if x[9999] != 0 { // ERROR "generated nil check" break } } - - x = fx10k() + + x = fx10k() _ = x[9999] // ERROR "generated nil check" if b { _ = x[9999] // ERROR "removed repeated nil check" } else { _ = x[9999] // ERROR "removed repeated nil check" - } + } _ = x[9999] // ERROR "generated nil check" - x = fx10k() + x = fx10k() if b { _ = x[9999] // ERROR "generated nil check" } else { _ = x[9999] // ERROR "generated nil check" - } + } _ = x[9999] // ERROR "generated nil check" - + fx10k() // This one is a bit redundant, if we figured out that // x wasn't going to change across the function call. @@ -145,7 +146,7 @@ func f3b() { _ = &x[9] // ERROR "removed repeated nil check" } -func fx10() *[10]int +func fx10() *[10]int func f4(x *[10]int) { // Most of these have no checks because a real memory reference follows, @@ -153,14 +154,14 @@ func f4(x *[10]int) { // in the first unmapped page of memory. _ = x[9] // ERROR "removed nil check before indirect" - + for { if x[9] != 0 { // ERROR "removed nil check before indirect" break } } - - x = fx10() + + x = fx10() _ = x[9] // ERROR "removed nil check before indirect" if b { _ = x[9] // ERROR "removed nil check before indirect" @@ -169,17 +170,17 @@ func f4(x *[10]int) { } _ = x[9] // ERROR "removed nil check before indirect" - x = fx10() + x = fx10() if b { _ = x[9] // ERROR "removed nil check before indirect" } else { _ = &x[9] // ERROR "generated nil check" - } + } _ = x[9] // ERROR "removed nil check before indirect" - + fx10() _ = x[9] // ERROR "removed nil check before indirect" - + x = fx10() y := fx10() _ = &x[9] // ERROR "generated nil check" @@ -188,4 +189,3 @@ func f4(x *[10]int) { x = y _ = &x[9] // ERROR "removed repeated nil check" } - -- 2.48.1