reg,pass: refactor allocation of aliased registers (#121)

Issue #100 demonstrated that register allocation for aliased registers is
fundamentally broken. The root of the issue is that currently accesses to the
same virtual register with different masks are treated as different registers.
This PR takes a different approach:

* Liveness analysis is masked: we now properly consider which parts of a register are live
* Register allocation produces a mapping from virtual to physical ID, and aliasing is applied later

In addition, a new pass ZeroExtend32BitOutputs accounts for the fact that 32-bit writes in 64-bit mode should actually be treated as 64-bit writes (the result is zero-extended).

Closes #100
This commit is contained in:
Michael McLoughlin
2020-01-22 22:50:40 -08:00
committed by GitHub
parent 126469f13d
commit f40d602170
33 changed files with 1241 additions and 362 deletions

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// +build ignore
package main
import (
. "github.com/mmcloughlin/avo/build"
. "github.com/mmcloughlin/avo/operand"
)
func main() {
TEXT("Issue100", NOSPLIT, "func() uint64")
x := GP64()
XORQ(x, x)
for i := 1; i <= 100; i++ {
t := GP64()
MOVQ(U32(i), t)
ADDQ(t.As64(), x)
}
Store(x, ReturnIndex(0))
RET()
Generate()
}

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// Package issue100 contains a reproducer for a bug in aliased register allocation.
package issue100

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// Code generated by command: go run asm.go -out issue100.s -stubs stub.go. DO NOT EDIT.
#include "textflag.h"
// func Issue100() uint64
TEXT ·Issue100(SB), NOSPLIT, $0-8
XORQ AX, AX
MOVQ $0x00000001, CX
ADDQ CX, AX
MOVQ $0x00000002, CX
ADDQ CX, AX
MOVQ $0x00000003, CX
ADDQ CX, AX
MOVQ $0x00000004, CX
ADDQ CX, AX
MOVQ $0x00000005, CX
ADDQ CX, AX
MOVQ $0x00000006, CX
ADDQ CX, AX
MOVQ $0x00000007, CX
ADDQ CX, AX
MOVQ $0x00000008, CX
ADDQ CX, AX
MOVQ $0x00000009, CX
ADDQ CX, AX
MOVQ $0x0000000a, CX
ADDQ CX, AX
MOVQ $0x0000000b, CX
ADDQ CX, AX
MOVQ $0x0000000c, CX
ADDQ CX, AX
MOVQ $0x0000000d, CX
ADDQ CX, AX
MOVQ $0x0000000e, CX
ADDQ CX, AX
MOVQ $0x0000000f, CX
ADDQ CX, AX
MOVQ $0x00000010, CX
ADDQ CX, AX
MOVQ $0x00000011, CX
ADDQ CX, AX
MOVQ $0x00000012, CX
ADDQ CX, AX
MOVQ $0x00000013, CX
ADDQ CX, AX
MOVQ $0x00000014, CX
ADDQ CX, AX
MOVQ $0x00000015, CX
ADDQ CX, AX
MOVQ $0x00000016, CX
ADDQ CX, AX
MOVQ $0x00000017, CX
ADDQ CX, AX
MOVQ $0x00000018, CX
ADDQ CX, AX
MOVQ $0x00000019, CX
ADDQ CX, AX
MOVQ $0x0000001a, CX
ADDQ CX, AX
MOVQ $0x0000001b, CX
ADDQ CX, AX
MOVQ $0x0000001c, CX
ADDQ CX, AX
MOVQ $0x0000001d, CX
ADDQ CX, AX
MOVQ $0x0000001e, CX
ADDQ CX, AX
MOVQ $0x0000001f, CX
ADDQ CX, AX
MOVQ $0x00000020, CX
ADDQ CX, AX
MOVQ $0x00000021, CX
ADDQ CX, AX
MOVQ $0x00000022, CX
ADDQ CX, AX
MOVQ $0x00000023, CX
ADDQ CX, AX
MOVQ $0x00000024, CX
ADDQ CX, AX
MOVQ $0x00000025, CX
ADDQ CX, AX
MOVQ $0x00000026, CX
ADDQ CX, AX
MOVQ $0x00000027, CX
ADDQ CX, AX
MOVQ $0x00000028, CX
ADDQ CX, AX
MOVQ $0x00000029, CX
ADDQ CX, AX
MOVQ $0x0000002a, CX
ADDQ CX, AX
MOVQ $0x0000002b, CX
ADDQ CX, AX
MOVQ $0x0000002c, CX
ADDQ CX, AX
MOVQ $0x0000002d, CX
ADDQ CX, AX
MOVQ $0x0000002e, CX
ADDQ CX, AX
MOVQ $0x0000002f, CX
ADDQ CX, AX
MOVQ $0x00000030, CX
ADDQ CX, AX
MOVQ $0x00000031, CX
ADDQ CX, AX
MOVQ $0x00000032, CX
ADDQ CX, AX
MOVQ $0x00000033, CX
ADDQ CX, AX
MOVQ $0x00000034, CX
ADDQ CX, AX
MOVQ $0x00000035, CX
ADDQ CX, AX
MOVQ $0x00000036, CX
ADDQ CX, AX
MOVQ $0x00000037, CX
ADDQ CX, AX
MOVQ $0x00000038, CX
ADDQ CX, AX
MOVQ $0x00000039, CX
ADDQ CX, AX
MOVQ $0x0000003a, CX
ADDQ CX, AX
MOVQ $0x0000003b, CX
ADDQ CX, AX
MOVQ $0x0000003c, CX
ADDQ CX, AX
MOVQ $0x0000003d, CX
ADDQ CX, AX
MOVQ $0x0000003e, CX
ADDQ CX, AX
MOVQ $0x0000003f, CX
ADDQ CX, AX
MOVQ $0x00000040, CX
ADDQ CX, AX
MOVQ $0x00000041, CX
ADDQ CX, AX
MOVQ $0x00000042, CX
ADDQ CX, AX
MOVQ $0x00000043, CX
ADDQ CX, AX
MOVQ $0x00000044, CX
ADDQ CX, AX
MOVQ $0x00000045, CX
ADDQ CX, AX
MOVQ $0x00000046, CX
ADDQ CX, AX
MOVQ $0x00000047, CX
ADDQ CX, AX
MOVQ $0x00000048, CX
ADDQ CX, AX
MOVQ $0x00000049, CX
ADDQ CX, AX
MOVQ $0x0000004a, CX
ADDQ CX, AX
MOVQ $0x0000004b, CX
ADDQ CX, AX
MOVQ $0x0000004c, CX
ADDQ CX, AX
MOVQ $0x0000004d, CX
ADDQ CX, AX
MOVQ $0x0000004e, CX
ADDQ CX, AX
MOVQ $0x0000004f, CX
ADDQ CX, AX
MOVQ $0x00000050, CX
ADDQ CX, AX
MOVQ $0x00000051, CX
ADDQ CX, AX
MOVQ $0x00000052, CX
ADDQ CX, AX
MOVQ $0x00000053, CX
ADDQ CX, AX
MOVQ $0x00000054, CX
ADDQ CX, AX
MOVQ $0x00000055, CX
ADDQ CX, AX
MOVQ $0x00000056, CX
ADDQ CX, AX
MOVQ $0x00000057, CX
ADDQ CX, AX
MOVQ $0x00000058, CX
ADDQ CX, AX
MOVQ $0x00000059, CX
ADDQ CX, AX
MOVQ $0x0000005a, CX
ADDQ CX, AX
MOVQ $0x0000005b, CX
ADDQ CX, AX
MOVQ $0x0000005c, CX
ADDQ CX, AX
MOVQ $0x0000005d, CX
ADDQ CX, AX
MOVQ $0x0000005e, CX
ADDQ CX, AX
MOVQ $0x0000005f, CX
ADDQ CX, AX
MOVQ $0x00000060, CX
ADDQ CX, AX
MOVQ $0x00000061, CX
ADDQ CX, AX
MOVQ $0x00000062, CX
ADDQ CX, AX
MOVQ $0x00000063, CX
ADDQ CX, AX
MOVQ $0x00000064, CX
ADDQ CX, AX
MOVQ AX, ret+0(FP)
RET

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package issue100
import (
"testing"
)
//go:generate go run asm.go -out issue100.s -stubs stub.go
func TestIssue100(t *testing.T) {
n := uint64(100)
expect := n * (n + 1) / 2
if got := Issue100(); got != expect {
t.Fatalf("Issue100() = %v; expect %v", got, expect)
}
}

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// Code generated by command: go run asm.go -out issue100.s -stubs stub.go. DO NOT EDIT.
package issue100
func Issue100() uint64

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// +build generate
//go:generate go run $GOFILE
// Regression test for a bug where casting a physical register would give the
// error "non physical register found".
//
// See: https://github.com/mmcloughlin/avo/issues/65#issuecomment-576850145
package main
import (
. "github.com/mmcloughlin/avo/build"
. "github.com/mmcloughlin/avo/operand"
. "github.com/mmcloughlin/avo/reg"
)
func main() {
TEXT("Issue65", NOSPLIT, "func()")
VINSERTI128(Imm(1), Y0.AsX(), Y1, Y2)
RET()
Generate()
}