[RISCV] Add support for getHostCPUFeatures using hwprobe #94352

dtcxzyw · 2024-06-04T13:14:45Z

This patch adds support for sys::getHostCPUFeatures using the RISC-V hardware probing interface.
References:

Loongarch patch: e53f41c
asm/hwprobe.h: https://github.com/torvalds/linux/blob/2ab79514109578fc4b6df90633d500cf281eb689/arch/riscv/include/uapi/asm/hwprobe.h
glibc support: https://inbox.sourceware.org/glibc-cvs/[email protected]/T/#Z2e.:..:20240301151728.AD5963858C53::40sourceware.org:1sysdeps:unix:sysv:linux:riscv:sys:hwprobe.h
__NR_riscv_hwprobe syscall tutorial: https://github.com/cyyself/hwprobe
hwprobe docs: https://docs.kernel.org/arch/riscv/hwprobe.html

Co-authored-by: @cyyself

Co-authored-by: Yangyu Chen <[email protected]>

llvm/lib/TargetParser/Host.cpp

tschuett · 2024-06-04T15:33:34Z

Do you offer an alternative/default implementation when __NR_riscv_hwprobe is not available, e.g., in docker containers?

dtcxzyw · 2024-06-05T15:08:26Z

Do you offer an alternative/default implementation when __NR_riscv_hwprobe is not available, e.g., in docker containers?

Is /proc/cpuinfo available in containers? If so, I can provide a fallback implementation by reading the isa field from this file.

cyyself · 2024-06-05T15:59:12Z

Do you offer an alternative/default implementation when __NR_riscv_hwprobe is not available, e.g., in docker containers?

Is /proc/cpuinfo available in containers? If so, I can provide a fallback implementation by reading the isa field from this file.

I think it is a bad idea. Some vendor custom kernels, such as t-head kernel, regard xtheadvector as v and printed in /proc/cpuinfo. A vast number of RISC-V devices still use these kernels.

dtcxzyw · 2024-06-10T13:51:48Z

Ping.

llvm/lib/TargetParser/Host.cpp

llvmbot · 2024-06-10T17:11:48Z

@llvm/pr-subscribers-backend-risc-v
@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-driver

Author: Yingwei Zheng (dtcxzyw)

Changes

This patch adds support for sys::getHostCPUFeatures using the RISC-V hardware probing interface.
References:

Loongarch patch: e53f41c
asm/hwprobe.h: https://github.com/torvalds/linux/blob/2ab79514109578fc4b6df90633d500cf281eb689/arch/riscv/include/uapi/asm/hwprobe.h
glibc support: https://inbox.sourceware.org/glibc-cvs/20240301151728.AD5963858C53@sourceware.org/T/#Z2e.:..:20240301151728.AD5963858C53::40sourceware.org:1sysdeps:unix:sysv:linux:riscv:sys:hwprobe.h
__NR_riscv_hwprobe syscall tutorial: https://github.com/cyyself/hwprobe
hwprobe docs: https://docs.kernel.org/6.5/riscv/hwprobe.html

Co-authored-by: @cyyself

Full diff: https://github.com/llvm/llvm-project/pull/94352.diff

2 Files Affected:

(modified) clang/lib/Driver/ToolChains/Arch/RISCV.cpp (+7-1)
(modified) llvm/lib/TargetParser/Host.cpp (+69)

diff --git a/clang/lib/Driver/ToolChains/Arch/RISCV.cpp b/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
index 2e2bce8494672..bf34b6e3f2ea4 100644
--- a/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
@@ -86,8 +86,14 @@ void riscv::getRISCVTargetFeatures(const Driver &D, const llvm::Triple &Triple,
   // and other features (ex. mirco architecture feature) from mcpu
   if (Arg *A = Args.getLastArg(options::OPT_mcpu_EQ)) {
     StringRef CPU = A->getValue();
-    if (CPU == "native")
+    if (CPU == "native") {
       CPU = llvm::sys::getHostCPUName();
+      llvm::StringMap<bool> HostFeatures;
+      if (llvm::sys::getHostCPUFeatures(HostFeatures))
+        for (auto &F : HostFeatures)
+          Features.push_back(
+              Args.MakeArgString((F.second ? "+" : "-") + F.first()));
+    }
 
     getRISCFeaturesFromMcpu(D, A, Triple, CPU, Features);
   }
diff --git a/llvm/lib/TargetParser/Host.cpp b/llvm/lib/TargetParser/Host.cpp
index 68155acd9e5bc..b99e1443ef5e5 100644
--- a/llvm/lib/TargetParser/Host.cpp
+++ b/llvm/lib/TargetParser/Host.cpp
@@ -1998,6 +1998,75 @@ bool sys::getHostCPUFeatures(StringMap<bool> &Features) {
 
   return true;
 }
+#elif defined(__linux__) && defined(__riscv)
+// struct riscv_hwprobe
+struct RISCVHwProbe {
+  int64_t Key;
+  uint64_t Value;
+};
+bool sys::getHostCPUFeatures(StringMap<bool> &Features) {
+  RISCVHwProbe Query[]{{/*RISCV_HWPROBE_KEY_BASE_BEHAVIOR=*/3, 0},
+                       {/*RISCV_HWPROBE_KEY_IMA_EXT_0=*/4, 0}};
+  int Ret = syscall(/*__NR_riscv_hwprobe=*/258, /*pairs=*/Query,
+                    /*pair_count=*/std::size(Query), /*cpu_count=*/0,
+                    /*cpus=*/0, /*flags=*/0);
+  if (Ret != 0)
+    return false;
+
+  uint64_t BaseMask = Query[0].Value;
+  // Check whether RISCV_HWPROBE_BASE_BEHAVIOR_IMA is set.
+  if (BaseMask & 1) {
+    Features["i"] = true;
+    Features["m"] = true;
+    Features["a"] = true;
+  }
+
+  uint64_t ExtMask = Query[1].Value;
+  Features["f"] = ExtMask & (1 << 0);           // RISCV_HWPROBE_IMA_FD
+  Features["d"] = ExtMask & (1 << 0);           // RISCV_HWPROBE_IMA_FD
+  Features["c"] = ExtMask & (1 << 1);           // RISCV_HWPROBE_IMA_C
+  Features["v"] = ExtMask & (1 << 2);           // RISCV_HWPROBE_IMA_V
+  Features["zba"] = ExtMask & (1 << 3);         // RISCV_HWPROBE_EXT_ZBA
+  Features["zbb"] = ExtMask & (1 << 4);         // RISCV_HWPROBE_EXT_ZBB
+  Features["zbs"] = ExtMask & (1 << 5);         // RISCV_HWPROBE_EXT_ZBS
+  Features["zicboz"] = ExtMask & (1 << 6);      // RISCV_HWPROBE_EXT_ZICBOZ
+  Features["zbc"] = ExtMask & (1 << 7);         // RISCV_HWPROBE_EXT_ZBC
+  Features["zbkb"] = ExtMask & (1 << 8);        // RISCV_HWPROBE_EXT_ZBKB
+  Features["zbkc"] = ExtMask & (1 << 9);        // RISCV_HWPROBE_EXT_ZBKC
+  Features["zbkx"] = ExtMask & (1 << 10);       // RISCV_HWPROBE_EXT_ZBKX
+  Features["zknd"] = ExtMask & (1 << 11);       // RISCV_HWPROBE_EXT_ZKND
+  Features["zkne"] = ExtMask & (1 << 12);       // RISCV_HWPROBE_EXT_ZKNE
+  Features["zknh"] = ExtMask & (1 << 13);       // RISCV_HWPROBE_EXT_ZKNH
+  Features["zksed"] = ExtMask & (1 << 14);      // RISCV_HWPROBE_EXT_ZKSED
+  Features["zksh"] = ExtMask & (1 << 15);       // RISCV_HWPROBE_EXT_ZKSH
+  Features["zkt"] = ExtMask & (1 << 16);        // RISCV_HWPROBE_EXT_ZKT
+  Features["zvbb"] = ExtMask & (1 << 17);       // RISCV_HWPROBE_EXT_ZVBB
+  Features["zvbc"] = ExtMask & (1 << 18);       // RISCV_HWPROBE_EXT_ZVBC
+  Features["zvkb"] = ExtMask & (1 << 19);       // RISCV_HWPROBE_EXT_ZVKB
+  Features["zvkg"] = ExtMask & (1 << 20);       // RISCV_HWPROBE_EXT_ZVKG
+  Features["zvkned"] = ExtMask & (1 << 21);     // RISCV_HWPROBE_EXT_ZVKNED
+  Features["zvknha"] = ExtMask & (1 << 22);     // RISCV_HWPROBE_EXT_ZVKNHA
+  Features["zvknhb"] = ExtMask & (1 << 23);     // RISCV_HWPROBE_EXT_ZVKNHB
+  Features["zvksed"] = ExtMask & (1 << 24);     // RISCV_HWPROBE_EXT_ZVKSED
+  Features["zvksh"] = ExtMask & (1 << 25);      // RISCV_HWPROBE_EXT_ZVKSH
+  Features["zvkt"] = ExtMask & (1 << 26);       // RISCV_HWPROBE_EXT_ZVKT
+  Features["zfh"] = ExtMask & (1 << 27);        // RISCV_HWPROBE_EXT_ZFH
+  Features["zfhmin"] = ExtMask & (1 << 28);     // RISCV_HWPROBE_EXT_ZFHMIN
+  Features["zihintntl"] = ExtMask & (1 << 29);  // RISCV_HWPROBE_EXT_ZIHINTNTL
+  Features["zvfh"] = ExtMask & (1 << 30);       // RISCV_HWPROBE_EXT_ZVFH
+  Features["zvfhmin"] = ExtMask & (1ULL << 31); // RISCV_HWPROBE_EXT_ZVFHMIN
+  Features["zfa"] = ExtMask & (1ULL << 32);     // RISCV_HWPROBE_EXT_ZFA
+  Features["ztso"] = ExtMask & (1ULL << 33);    // RISCV_HWPROBE_EXT_ZTSO
+  Features["zacas"] = ExtMask & (1ULL << 34);   // RISCV_HWPROBE_EXT_ZACAS
+  Features["zicond"] = ExtMask & (1ULL << 35);  // RISCV_HWPROBE_EXT_ZICOND
+  Features["zihintpause"] =
+      ExtMask & (1ULL << 36); // RISCV_HWPROBE_EXT_ZIHINTPAUSE
+
+  // TODO: set unaligned-scalar-mem if RISCV_HWPROBE_KEY_MISALIGNED_PERF returns
+  // RISCV_HWPROBE_MISALIGNED_FAST.
+
+  return true;
+}
 #else
 bool sys::getHostCPUFeatures(StringMap<bool> &Features) { return false; }
 #endif

wangpc-pp · 2024-06-11T04:32:53Z

clang/lib/Driver/ToolChains/Arch/RISCV.cpp

      CPU = llvm::sys::getHostCPUName();
+      llvm::StringMap<bool> HostFeatures;
+      if (llvm::sys::getHostCPUFeatures(HostFeatures))


Open discussion here: CPU may fail and return generic. Should we failback to use getHostCPUFeatures if getHostCPUName fails? Or we should use getHostCPUFeatures all the time?

I think hwprobe is more reliable than cpu name because some RV cpus are not recognized by LLVM (e.g., T-head's cores). However, cpu name is still useful even if getHostCPUFeatures returns true because it may provide scheduling model.

topperc

LGTM

dtcxzyw · 2024-06-22T17:25:42Z

I have no idea about why it corrupts StringMap. Sad :(

llvm/lib/TargetParser/Host.cpp

clang/lib/Driver/ToolChains/Arch/RISCV.cpp

This reverts commit 7563384.

clang/lib/Driver/ToolChains/Arch/RISCV.cpp

github-actions · 2024-07-07T17:20:54Z

✅ With the latest revision this PR passed the C/C++ code formatter.

…`. NFC. (#97965) See the discussion in #94352 (comment)

topperc

LGTM

dtcxzyw · 2024-07-13T08:21:24Z

I will rebase on the top of #97824.

dtcxzyw · 2024-07-13T09:01:22Z

dtcxzyw@bananapif3:/data/llvm-build$ bin/clang -mcpu=native --print-enabled-extensions
clang version 19.0.0git
Target: riscv64-unknown-linux-gnu
Thread model: posix
InstalledDir: /data/llvm-build/bin
Build config: +assertions
Extensions enabled for the given RISC-V target

    Name                 Version   Description
    i                    2.1       'I' (Base Integer Instruction Set)
    m                    2.0       'M' (Integer Multiplication and Division)
    a                    2.1       'A' (Atomic Instructions)
    f                    2.2       'F' (Single-Precision Floating-Point)
    d                    2.2       'D' (Double-Precision Floating-Point)
    c                    2.0       'C' (Compressed Instructions)
    v                    1.0       'V' (Vector Extension for Application Processors)
    zicond               1.0       'Zicond' (Integer Conditional Operations)
    zicsr                2.0       'zicsr' (CSRs)
    zihintpause          2.0       'Zihintpause' (Pause Hint)
    zmmul                1.0       'Zmmul' (Integer Multiplication)
    zba                  1.0       'Zba' (Address Generation Instructions)
    zbb                  1.0       'Zbb' (Basic Bit-Manipulation)
    zbc                  1.0       'Zbc' (Carry-Less Multiplication)
    zbs                  1.0       'Zbs' (Single-Bit Instructions)
    zve32f               1.0       'Zve32f' (Vector Extensions for Embedded Processors with maximal 32 EEW and F extension)
    zve32x               1.0       'Zve32x' (Vector Extensions for Embedded Processors with maximal 32 EEW)
    zve64d               1.0       'Zve64d' (Vector Extensions for Embedded Processors with maximal 64 EEW, F and D extension)
    zve64f               1.0       'Zve64f' (Vector Extensions for Embedded Processors with maximal 64 EEW and F extension)
    zve64x               1.0       'Zve64x' (Vector Extensions for Embedded Processors with maximal 64 EEW)
    zvl128b              1.0       'Zvl' (Minimum Vector Length) 128
    zvl32b               1.0       'Zvl' (Minimum Vector Length) 32
    zvl64b               1.0       'Zvl' (Minimum Vector Length) 64

Experimental extensions

ISA String: rv64i2p1_m2p0_a2p1_f2p2_d2p2_c2p0_v1p0_zicond1p0_zicsr2p0_zihintpause2p0_zmmul1p0_zba1p0_zbb1p0_zbc1p0_zbs1p0_zve32f1p0_zve32x1p0_zve64d1p0_zve64f1p0_zve64x1p0_zvl128b1p0_zvl32b1p0_zvl64b1p0
dtcxzyw@bananapif3:/data/llvm-build$

dtcxzyw · 2024-07-13T09:05:47Z

Ping @wangpc-pp @topperc @preames

…`. NFC. (llvm#97965) See the discussion in llvm#94352 (comment)

clang/lib/Driver/ToolChains/Arch/RISCV.cpp

wangpc-pp

LGTM.

Summary: This patch adds support for `sys::getHostCPUFeatures` using the RISC-V hardware probing interface. References: + Loongarch patch: e53f41c + asm/hwprobe.h: https://github.com/torvalds/linux/blob/2ab79514109578fc4b6df90633d500cf281eb689/arch/riscv/include/uapi/asm/hwprobe.h + glibc support: https://inbox.sourceware.org/glibc-cvs/[email protected]/T/#Z2e.:..:20240301151728.AD5963858C53::40sourceware.org:1sysdeps:unix:sysv:linux:riscv:sys:hwprobe.h + __NR_riscv_hwprobe syscall tutorial: https://github.com/cyyself/hwprobe + hwprobe docs: https://docs.kernel.org/arch/riscv/hwprobe.html --------- Co-authored-by: Yangyu Chen <[email protected]> Test Plan: Reviewers: Subscribers: Tasks: Tags: Differential Revision: https://phabricator.intern.facebook.com/D60251727

This patch is the follow-up of #94352 with some updates: 1. Add support for more extensions for `zve*`, `zimop`, `zc*`, `zcmop` and `zawrs`. 2. Use `RISCV_HWPROBE_KEY_MISALIGNED_SCALAR_PERF` to check whether the processor supports fast misaligned scalar memory access. #108551 reminds me that the patch https://lore.kernel.org/all/[email protected]/T/ has been merged. Address comment #94352 (comment). References: 1. constants: https://github.com/torvalds/linux/blame/v6.11-rc7/arch/riscv/include/uapi/asm/hwprobe.h 2. https://docs.kernel.org/arch/riscv/hwprobe.html 3. Related commits: 1. `zve*` support: torvalds/linux@de8f828 2. `zimop` support: torvalds/linux@36f8960 3. `zc*` support: torvalds/linux@0ad70db 4. `zcmop` support: torvalds/linux@fc078ea 5. `zawrs` support: torvalds/linux@244c18f 6. scalar misaligned perf: torvalds/linux@c42e2f0 and torvalds/linux@1f52888

[RISCV] Add support for getHostCPUFeatures using hwprobe

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Co-authored-by: Yangyu Chen <[email protected]>

dtcxzyw requested review from MaskRay, BeMg, topperc and wangpc-pp June 4, 2024 13:14

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[RISCV] Address review comments.

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dtcxzyw added 2 commits June 11, 2024 01:09

[RISCV] Check IMA

f3f61d6

[Clang][RISCV] Add clang -mcpu=native support

212ddab

llvmbot added clang Clang issues not falling into any other category backend:RISC-V clang:driver 'clang' and 'clang++' user-facing binaries. Not 'clang-cl' labels Jun 10, 2024

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dtcxzyw requested review from preames, lukel97 and kito-cheng June 15, 2024 00:36

dtcxzyw added 2 commits June 22, 2024 16:31

[RISCV] Fix generic targets

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[RISCV] Fix typo. NFC.

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[RISCV] Detect target features in riscv::getRISCVArch

7563384

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Revert "[RISCV] Detect target features in riscv::getRISCVArch"

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This reverts commit 7563384.

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dtcxzyw added 2 commits July 8, 2024 00:45

Merge branch 'main' into rv-native-hwprobe

7ce92bb

[RISCV][Driver] Remove Args.MakeArgString

6be7eea

dtcxzyw mentioned this pull request Jul 7, 2024

[RISCV][Driver] Refactor riscv::getRISCVArch to return std::string. NFC. #97965

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dtcxzyw added a commit that referenced this pull request Jul 9, 2024

[RISCV][Driver] Refactor riscv::getRISCVArch to return `std::string…

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…`. NFC. (#97965) See the discussion in #94352 (comment)

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dtcxzyw added 4 commits July 10, 2024 15:46

Merge branch 'main' into rv-native-hwprobe

33c063e

[RISCV] Format code. NFC.

a515f3b

Reland [RISCV] Add support for getHostCPUFeatures using hwprobe

ad887bc

[RISCV] Set ztso

208a172

dtcxzyw added 2 commits July 13, 2024 16:31

Merge branch 'main' into rv-native-hwprobe

4acb528

[RISCV] Fix compilation error

adbb036

[RISCV] Fallback when hwprobe is unavailable

6b6fd88

aaryanshukla pushed a commit to aaryanshukla/llvm-project that referenced this pull request Jul 14, 2024

[RISCV][Driver] Refactor riscv::getRISCVArch to return `std::string…

85fa710

…`. NFC. (llvm#97965) See the discussion in llvm#94352 (comment)

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Merge branch 'main' into rv-native-hwprobe

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[RISCV][Clang] Address review comments.

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dtcxzyw merged commit 578cf72 into llvm:main Jul 16, 2024
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[RISCV] Bump hwprobe support to Linux 6.11 #108578

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