8f28e8069c
Generate store immediate instruction when CPUv4 is enabled.
For example:
$ cat test.c
struct foo {
unsigned char b;
unsigned short h;
unsigned int w;
unsigned long d;
};
void bar(volatile struct foo *p) {
p->b = 1;
p->h = 2;
p->w = 3;
p->d = 4;
}
$ clang -O2 --target=bpf -mcpu=v4 test.c -c -o - | llvm-objdump -d -
...
0000000000000000 <bar>:
0: 72 01 00 00 01 00 00 00 *(u8 *)(r1 + 0x0) = 0x1
1: 6a 01 02 00 02 00 00 00 *(u16 *)(r1 + 0x2) = 0x2
2: 62 01 04 00 03 00 00 00 *(u32 *)(r1 + 0x4) = 0x3
3: 7a 01 08 00 04 00 00 00 *(u64 *)(r1 + 0x8) = 0x4
4: 95 00 00 00 00 00 00 00 exit
Take special care to:
- apply `BPFMISimplifyPatchable::checkADDrr` rewrite for BPF_ST
- validate immediate value when BPF_ST write is 64-bit:
BPF interprets `(BPF_ST | BPF_MEM | BPF_DW)` writes as writes with
sign extension. Thus it is fine to generate such write when
immediate is -1, but it is incorrect to generate such write when
immediate is +0xffff_ffff.
This commit was previously reverted in e66affa17e.
The reason for revert was an unrelated bug in BPF backend,
triggered by test case added in this commit if LLVM is built
with LLVM_ENABLE_EXPENSIVE_CHECKS.
The bug was fixed in D157806.
Differential Revision: https://reviews.llvm.org/D140804
97 lines
3.0 KiB
C++
97 lines
3.0 KiB
C++
//===-- BPFSubtarget.cpp - BPF Subtarget Information ----------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the BPF specific subclass of TargetSubtargetInfo.
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//
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//===----------------------------------------------------------------------===//
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#include "BPFSubtarget.h"
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#include "BPF.h"
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#include "llvm/MC/TargetRegistry.h"
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#include "llvm/TargetParser/Host.h"
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using namespace llvm;
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#define DEBUG_TYPE "bpf-subtarget"
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#define GET_SUBTARGETINFO_TARGET_DESC
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#define GET_SUBTARGETINFO_CTOR
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#include "BPFGenSubtargetInfo.inc"
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static cl::opt<bool> Disable_ldsx("disable-ldsx", cl::Hidden, cl::init(false),
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cl::desc("Disable ldsx insns"));
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static cl::opt<bool> Disable_movsx("disable-movsx", cl::Hidden, cl::init(false),
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cl::desc("Disable movsx insns"));
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static cl::opt<bool> Disable_bswap("disable-bswap", cl::Hidden, cl::init(false),
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cl::desc("Disable bswap insns"));
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static cl::opt<bool> Disable_sdiv_smod("disable-sdiv-smod", cl::Hidden,
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cl::init(false), cl::desc("Disable sdiv/smod insns"));
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static cl::opt<bool> Disable_gotol("disable-gotol", cl::Hidden, cl::init(false),
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cl::desc("Disable gotol insn"));
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static cl::opt<bool>
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Disable_StoreImm("disable-storeimm", cl::Hidden, cl::init(false),
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cl::desc("Disable BPF_ST (immediate store) insn"));
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void BPFSubtarget::anchor() {}
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BPFSubtarget &BPFSubtarget::initializeSubtargetDependencies(StringRef CPU,
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StringRef FS) {
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initializeEnvironment();
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initSubtargetFeatures(CPU, FS);
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ParseSubtargetFeatures(CPU, /*TuneCPU*/ CPU, FS);
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return *this;
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}
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void BPFSubtarget::initializeEnvironment() {
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HasJmpExt = false;
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HasJmp32 = false;
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HasAlu32 = false;
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UseDwarfRIS = false;
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HasLdsx = false;
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HasMovsx = false;
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HasBswap = false;
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HasSdivSmod = false;
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HasGotol = false;
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HasStoreImm = false;
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}
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void BPFSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
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if (CPU == "probe")
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CPU = sys::detail::getHostCPUNameForBPF();
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if (CPU == "generic" || CPU == "v1")
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return;
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if (CPU == "v2") {
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HasJmpExt = true;
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return;
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}
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if (CPU == "v3") {
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HasJmpExt = true;
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HasJmp32 = true;
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HasAlu32 = true;
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return;
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}
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if (CPU == "v4") {
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HasJmpExt = true;
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HasJmp32 = true;
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HasAlu32 = true;
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HasLdsx = !Disable_ldsx;
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HasMovsx = !Disable_movsx;
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HasBswap = !Disable_bswap;
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HasSdivSmod = !Disable_sdiv_smod;
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HasGotol = !Disable_gotol;
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HasStoreImm = !Disable_StoreImm;
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return;
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}
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}
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BPFSubtarget::BPFSubtarget(const Triple &TT, const std::string &CPU,
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const std::string &FS, const TargetMachine &TM)
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: BPFGenSubtargetInfo(TT, CPU, /*TuneCPU*/ CPU, FS),
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FrameLowering(initializeSubtargetDependencies(CPU, FS)),
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TLInfo(TM, *this) {}
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