cmd/compile: simplify shifts using bounds from prove pass
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>
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