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cmd/compile: simplify shifts using bounds from prove pass

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The prove pass sometimes has bounds information
that later rewrite passes do not.

Use this information to mark shifts as bounded,
and then use that information to generate better code on amd64.
It may prove to be helpful on other architectures, too.

While here, coalesce the existing shift lowering rules.

This triggers 35 times building std+cmd. The full list is below.

Here's an example from runtime.heapBitsSetType:

			if nb < 8 {
				b |= uintptr(*p) << nb
				p = add1(p)
			} else {
				nb -= 8
			}

We now generate better code on amd64 for that left shift.

Updates #25087

vendor/golang_org/x/crypto/curve25519/mont25519_amd64.go:48:20: Proved Rsh8Ux64 bounded
runtime/mbitmap.go:1252:22: Proved Lsh64x64 bounded
runtime/mbitmap.go:1265:16: Proved Lsh64x64 bounded
runtime/mbitmap.go:1275:28: Proved Lsh64x64 bounded
runtime/mbitmap.go:1645:25: Proved Lsh64x64 bounded
runtime/mbitmap.go:1663:25: Proved Lsh64x64 bounded
runtime/mbitmap.go:1808:41: Proved Lsh64x64 bounded
runtime/mbitmap.go:1831:49: Proved Lsh64x64 bounded
syscall/route_bsd.go:227:23: Proved Lsh32x64 bounded
syscall/route_bsd.go:295:23: Proved Lsh32x64 bounded
syscall/route_darwin.go:40:23: Proved Lsh32x64 bounded
compress/bzip2/bzip2.go:384:26: Proved Lsh64x16 bounded
vendor/golang_org/x/net/route/address.go:370:14: Proved Lsh64x64 bounded
compress/flate/inflate.go:201:54: Proved Lsh64x64 bounded
math/big/prime.go:50:25: Proved Lsh64x64 bounded
vendor/golang_org/x/crypto/cryptobyte/asn1.go:464:43: Proved Lsh8x8 bounded
net/ip.go:87:21: Proved Rsh8Ux64 bounded
cmd/internal/goobj/read.go:267:23: Proved Lsh64x64 bounded
cmd/vendor/golang.org/x/arch/arm64/arm64asm/decode.go:534:27: Proved Lsh32x32 bounded
cmd/vendor/golang.org/x/arch/arm64/arm64asm/decode.go:544:27: Proved Lsh32x32 bounded
cmd/internal/obj/arm/asm5.go:1044:16: Proved Lsh32x64 bounded
cmd/internal/obj/arm/asm5.go:1065:10: Proved Lsh32x32 bounded
cmd/internal/obj/mips/obj0.go:1311:21: Proved Lsh32x64 bounded
cmd/compile/internal/syntax/scanner.go:352:23: Proved Lsh64x64 bounded
go/types/expr.go:222:36: Proved Lsh64x64 bounded
crypto/x509/x509.go:1626:9: Proved Rsh8Ux64 bounded
cmd/link/internal/loadelf/ldelf.go:823:22: Proved Lsh8x64 bounded
net/http/h2_bundle.go:1470:17: Proved Lsh8x8 bounded
net/http/h2_bundle.go:1477:46: Proved Lsh8x8 bounded
net/http/h2_bundle.go:1481:31: Proved Lsh64x8 bounded
cmd/compile/internal/ssa/rewriteARM64.go:18759:17: Proved Lsh64x64 bounded
cmd/compile/internal/ssa/sparsemap.go:70:23: Proved Lsh32x64 bounded
cmd/compile/internal/ssa/sparsemap.go:73:45: Proved Lsh32x64 bounded

Change-Id: I58bb72f3e6f12f6ac69be633ea7222c245438142
Reviewed-on: https://go-review.googlesource.com/109776
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Giovanni Bajo <rasky@develer.com>
This commit is contained in:
Josh Bleecher Snyder 2018-04-26 20:56:03 -07:00
parent 22ff9521da
commit 9eb4590ad2
6 changed files with 1116 additions and 150 deletions
Download patch file Download diff file Expand all files Collapse all files

27
src/cmd/compile/internal/ssa/prove.go
View file

@ -972,6 +972,33 @@ func simplifyBlock(sdom SparseTree, ft *factsTable, b *Block) {
}
v.Op = ctzNonZeroOp[v.Op]
}
case OpLsh8x8, OpLsh8x16, OpLsh8x32, OpLsh8x64,
OpLsh16x8, OpLsh16x16, OpLsh16x32, OpLsh16x64,
OpLsh32x8, OpLsh32x16, OpLsh32x32, OpLsh32x64,
OpLsh64x8, OpLsh64x16, OpLsh64x32, OpLsh64x64,
OpRsh8x8, OpRsh8x16, OpRsh8x32, OpRsh8x64,
OpRsh16x8, OpRsh16x16, OpRsh16x32, OpRsh16x64,
OpRsh32x8, OpRsh32x16, OpRsh32x32, OpRsh32x64,
OpRsh64x8, OpRsh64x16, OpRsh64x32, OpRsh64x64,
OpRsh8Ux8, OpRsh8Ux16, OpRsh8Ux32, OpRsh8Ux64,
OpRsh16Ux8, OpRsh16Ux16, OpRsh16Ux32, OpRsh16Ux64,
OpRsh32Ux8, OpRsh32Ux16, OpRsh32Ux32, OpRsh32Ux64,
OpRsh64Ux8, OpRsh64Ux16, OpRsh64Ux32, OpRsh64Ux64:
// Check whether, for a << b, we know that b
// is strictly less than the number of bits in a.
by := v.Args[1]
lim, ok := ft.limits[by.ID]
if !ok {
continue
}
bits := 8 * v.Args[0].Type.Size()
if lim.umax < uint64(bits) || (lim.max < bits && ft.isNonNegative(by)) {
v.Aux = true
if b.Func.pass.debug > 0 {
b.Func.Warnl(v.Pos, "Proved %v bounded", v.Op)
}
}
}
}