[X86] Report error if the amx enabled on the non-64-bits target

[LiuChen3]

Summary

For now we check if the amx intrinsics used on 64-bits target. This
check is not accurate.

[pengfei]

LGTM, but maybe wait one day or two for other FE folks' opinions. @aaron.ballman

[aaron.ballman]

I think the precommit CI failures might be relevant here -- can you double-check those?

[craig.topper]

How does this interact with -march=native -m32. Won't that pick up the amx flag from CPUID?

[LiuChen3]

In D131134#3699742, @craig.topper wrote:

How does this interact with -march=native -m32. Won't that pick up the amx flag from CPUID?

In D131134#3699344, @aaron.ballman wrote:

I think the precommit CI failures might be relevant here -- can you double-check those?

Yes. This test is only supported on amdgpu-registered-target so I didn't catch this fail on my local machine. Thanks for point out.

[LiuChen3]

In D131134#3699742, @craig.topper wrote:

How does this interact with -march=native -m32. Won't that pick up the amx flag from CPUID?

Good point. I will continue the work.

[LiuChen3]

fix lit fail and handle '-march=native'

[LiuChen3]

change the error report

[craig.topper]

clang/lib/Driver/ToolChains/Arch/X86.cpp

133

This looks like it would trigger an error with -march=native -m32 on a cpu with amx? Why is that a desirable behavior? The compiler user has done nothing wrong. What are they supposed to do to avoid the error?

[craig.topper]

What problem are we trying to solve here? CPUID reports AMX as supported even in 32-bit mode. Why can't the user pass it to the compiler?

[LiuChen3]

In D131134#3707397, @craig.topper wrote:

What problem are we trying to solve here? CPUID reports AMX as supported even in 32-bit mode. Why can't the user pass it to the compiler?

I thought AMX is only supported on 64-bit mode. It seems I was wrong. So for now just reporting an error to intrinsics is enough. Thanks.

[pengfei]

I have the same impression. I checked ISE says AMX instructions are N.E. on 32-bit mode. And seems Linux Kernel only enables AMX on 64-bit too https://lwn.net/ml/linux-kernel/[e-mail]/#t

[craig.topper]

Yes AMX is only supported in 64-bit mode but I doubt CPUID checks which mode the program is running in.

[pengfei]

In D131134#3714860, @craig.topper wrote:

Yes AMX is only supported in 64-bit mode but I doubt CPUID checks which mode the program is running in.

I guess HasAMXSave is false on 32-bit mode https://github.com/llvm/llvm-project/blob/main/llvm/lib/Support/Host.cpp#L1800. But I don't have the environment to check it.

[pengfei]

In D131134#3715024, @pengfei wrote:

In D131134#3714860, @craig.topper wrote:

Yes AMX is only supported in 64-bit mode but I doubt CPUID checks which mode the program is running in.

I guess HasAMXSave is false on 32-bit mode https://github.com/llvm/llvm-project/blob/main/llvm/lib/Support/Host.cpp#L1800. But I don't have the environment to check it.

I found it. The XFEATURE_MASK_XTILE in Kernel is the same as HasAMXSave in compiler: https://lwn.net/ml/linux-kernel/[e-mail]/
So these features bits are true only on 64-bit mode.

[craig.topper]

In D131134#3715062, @pengfei wrote:

In D131134#3715024, @pengfei wrote:

In D131134#3714860, @craig.topper wrote:

Yes AMX is only supported in 64-bit mode but I doubt CPUID checks which mode the program is running in.

I guess HasAMXSave is false on 32-bit mode https://github.com/llvm/llvm-project/blob/main/llvm/lib/Support/Host.cpp#L1800. But I don't have the environment to check it.

I found it. The XFEATURE_MASK_XTILE in Kernel is the same as HasAMXSave in compiler: https://lwn.net/ml/linux-kernel/[e-mail]/
So these features bits are true only on 64-bit mode.

Is it cleared when running a 32-bit binary on a 64-bit kernel?

[pengfei]

In D131134#3715079, @craig.topper wrote:

In D131134#3715062, @pengfei wrote:

In D131134#3715024, @pengfei wrote:

In D131134#3714860, @craig.topper wrote:

Yes AMX is only supported in 64-bit mode but I doubt CPUID checks which mode the program is running in.

I guess HasAMXSave is false on 32-bit mode https://github.com/llvm/llvm-project/blob/main/llvm/lib/Support/Host.cpp#L1800. But I don't have the environment to check it.

I found it. The XFEATURE_MASK_XTILE in Kernel is the same as HasAMXSave in compiler: https://lwn.net/ml/linux-kernel/[e-mail]/
So these features bits are true only on 64-bit mode.

Is it cleared when running a 32-bit binary on a 64-bit kernel?

No, a 32-bit binary gets the same CR0 as 64-bit on a 64-bit kernel. Actually, it's compiler to get the CR0 rather than the binary it builds. It should be rare to run 32-bit compiler on 64-bit kernel.
So you are right. No matter 32 or 64 bits compiler, when it builds a binary with -m32 on 64-bit kernel with -march=native, it always sets AMX features. Maybe we should reset them to false when compile for 32-bit?

clang/include/clang/Basic/DiagnosticCommonKinds.td

 def err_opt_not_valid_with_opt : Error<
   "option '%0' cannot be specified with '%1'">;
 def err_opt_not_valid_without_opt : Error<
   "option '%0' cannot be specified without '%1'">;
 def err_opt_not_valid_on_target : Error<
   "option '%0' cannot be specified on this target">;
 def err_invalid_feature_combination : Error<
   "invalid feature combination: %0">;
+def err_feature_unsupported_on_target : Error<
+  "feature '%0' is not supported for %1 architecture">;
 
 // Source manager
 def err_cannot_open_file : Error<"cannot open file '%0': %1">, DefaultFatal;
 def err_file_modified : Error<
   "file '%0' modified since it was first processed">, DefaultFatal;
 def err_file_too_large : Error<
   "sorry, unsupported: file '%0' is too large for Clang to process">;
 def err_include_too_large : Error<

clang/lib/Basic/Targets/X86.cpp

void X86TargetInfo::setFeatureEnabled(llvm::StringMap<bool> &Features,
   Features[Name] = Enabled;
   llvm::X86::updateImpliedFeatures(Name, Enabled, Features);
 }
 
 /// handleTargetFeatures - Perform initialization based on the user
 /// configured set of features.
 bool X86TargetInfo::handleTargetFeatures(std::vector<std::string> &Features,
                                          DiagnosticsEngine &Diags) {
+  bool Is64bitTarget = getTriple().getArch() != llvm::Triple::x86;
   for (const auto &Feature : Features) {
     if (Feature[0] != '+')
       continue;
 
     if (Feature == "+aes") {
       HasAES = true;
     } else if (Feature == "+vaes") {
       HasVAES = true;
if (Feature == "+aes") {
       HasPTWRITE = true;
     } else if (Feature == "+invpcid") {
       HasINVPCID = true;
     } else if (Feature == "+enqcmd") {
       HasENQCMD = true;
     } else if (Feature == "+hreset") {
       HasHRESET = true;
     } else if (Feature == "+amx-bf16") {
+      if (!Is64bitTarget)
+        Diags.Report(diag::err_opt_not_valid_on_target) << "-mamx-bf16";
       HasAMXBF16 = true;
     } else if (Feature == "+amx-int8") {
+      if (!Is64bitTarget)
+        Diags.Report(diag::err_opt_not_valid_on_target) << "-mamx-int8";
       HasAMXINT8 = true;
     } else if (Feature == "+amx-tile") {
+      if (!Is64bitTarget)
+        Diags.Report(diag::err_opt_not_valid_on_target) << "-mamx-tile";
       HasAMXTILE = true;
     } else if (Feature == "+avxvnni") {
       HasAVXVNNI = true;
     } else if (Feature == "+serialize") {
       HasSERIALIZE = true;
     } else if (Feature == "+tsxldtrk") {
       HasTSXLDTRK = true;
     } else if (Feature == "+uintr") {

clang/lib/Driver/ToolChains/Arch/X86.cpp

std::string x86::getX86TargetCPU(const Driver &D, const ArgList &Args,
   }
 }
 
 void x86::getX86TargetFeatures(const Driver &D, const llvm::Triple &Triple,
                                const ArgList &Args,
                                std::vector<StringRef> &Features) {
   // If -march=native, autodetect the feature list.
   if (const Arg *A = Args.getLastArg(clang::driver::options::OPT_march_EQ)) {
+    bool Is64bitTarget = Triple.getArch() != llvm::Triple::x86;
     if (StringRef(A->getValue()) == "native") {
       llvm::StringMap<bool> HostFeatures;
       if (llvm::sys::getHostCPUFeatures(HostFeatures))
-        for (auto &F : HostFeatures)
+        for (auto &F : HostFeatures) {
+          if (F.first().startswith("amx") && F.second && !Is64bitTarget)
+            D.Diag(diag::err_feature_unsupported_on_target)
+                << F.first() << Triple.getArchName();
           Features.push_back(
               Args.MakeArgString((F.second ? "+" : "-") + F.first()));
         }
     }
+  }
 
   if (Triple.getArchName() == "x86_64h") {
     // x86_64h implies quite a few of the more modern subtarget features
     // for Haswell class CPUs, but not all of them. Opt-out of a few.
     Features.push_back("-rdrnd");
     Features.push_back("-aes");
     Features.push_back("-pclmul");
     Features.push_back("-rtm");

clang/test/Driver/x86-target-features.c

 // KL: "-target-feature" "+kl"
 // NO-KL: "-target-feature" "-kl"
 
 // RUN: %clang -target i386-linux-gnu -mwidekl %s -### 2>&1 | FileCheck -check-prefix=WIDE_KL %s
 // RUN: %clang -target i386-linux-gnu -mno-widekl %s -### 2>&1 | FileCheck -check-prefix=NO-WIDE_KL %s
 // WIDE_KL: "-target-feature" "+widekl"
 // NO-WIDE_KL: "-target-feature" "-widekl"
 
-// RUN: %clang --target=i386 -march=i386 -mamx-tile %s -### 2>&1 | FileCheck --check-prefix=AMX-TILE %s
-// RUN: %clang --target=i386 -march=i386 -mno-amx-tile %s -### 2>&1 | FileCheck --check-prefix=NO-AMX-TILE %s
+// RUN: %clang --target=x86_64 -march=x86-64 -mamx-tile %s -### 2>&1 | FileCheck --check-prefix=AMX-TILE %s
+// RUN: %clang --target=x86_64 -march=x86-64 -mno-amx-tile %s -### 2>&1 | FileCheck --check-prefix=NO-AMX-TILE %s
+// RUN: not %clang --target=i386 -march=i386 -mamx-tile %s 2>&1 | FileCheck %s -check-prefix=AMX-TILE-ERROR
 // AMX-TILE: "-target-feature" "+amx-tile"
 // NO-AMX-TILE: "-target-feature" "-amx-tile"
+// AMX-TILE-ERROR: error: option '-mamx-tile' cannot be specified on this target
 
-// RUN: %clang --target=i386 -march=i386 -mamx-bf16 %s -### 2>&1 | FileCheck --check-prefix=AMX-BF16 %s
-// RUN: %clang --target=i386 -march=i386 -mno-amx-bf16 %s -### 2>&1 | FileCheck -check-prefix=NO-AMX-BF16 %s
+// RUN: %clang --target=x86_64 -march=x86-64 -mamx-bf16 %s -### 2>&1 | FileCheck --check-prefix=AMX-BF16 %s
+// RUN: %clang --target=x86_64 -march=x86-64 -mno-amx-bf16 %s -### 2>&1 | FileCheck -check-prefix=NO-AMX-BF16 %s
+// RUN: not %clang --target=i386 -march=i386 -mamx-bf16 %s 2>&1 | FileCheck -check-prefix=AMX-BF16-ERROR %s
 // AMX-BF16: "-target-feature" "+amx-bf16"
 // NO-AMX-BF16: "-target-feature" "-amx-bf16"
+// AMX-BF16-ERROR: error: option '-mamx-bf16' cannot be specified on this target
 
-// RUN: %clang --target=i386 -march=i386 -mamx-int8 %s -### 2>&1 | FileCheck --check-prefix=AMX-INT8 %s
-// RUN: %clang --target=i386 -march=i386 -mno-amx-int8 %s -### 2>&1 | FileCheck --check-prefix=NO-AMX-INT8 %s
+// RUN: %clang --target=x86_64 -march=x86-64 -mamx-int8 %s -### 2>&1 | FileCheck --check-prefix=AMX-INT8 %s
+// RUN: %clang --target=x86_64 -march=x86-64 -mno-amx-int8 %s -### 2>&1 | FileCheck --check-prefix=NO-AMX-INT8 %s
+// RUN: not %clang --target=i386 -march=i386 -mamx-int8 %s 2>&1 | FileCheck -check-prefix=AMX-INT8-ERROR %s
 // AMX-INT8: "-target-feature" "+amx-int8"
 // NO-AMX-INT8: "-target-feature" "-amx-int8"
+// AMX-INT8-ERROR: error: option '-mamx-int8' cannot be specified on this target
 
 // RUN: %clang --target=i386 -march=i386 -mhreset %s -### 2>&1 | FileCheck -check-prefix=HRESET %s
 // RUN: %clang --target=i386 -march=i386 -mno-hreset %s -### 2>&1 | FileCheck -check-prefix=NO-HRESET %s
 // HRESET: "-target-feature" "+hreset"
 // NO-HRESET: "-target-feature" "-hreset"
 
 // RUN: %clang --target=i386 -march=i386 -muintr %s -### 2>&1 | FileCheck -check-prefix=UINTR %s
 // RUN: %clang --target=i386 -march=i386 -mno-uintr %s -### 2>&1 | FileCheck -check-prefix=NO-UINTR %s

clang/test/Preprocessor/predefined-arch-macros.c

 // CHECK_TGL_M64: #define __tune_corei7__ 1
 // CHECK_TGL_M64: #define __x86_64 1
 // CHECK_TGL_M64: #define __x86_64__ 1
 
 // RUN: %clang -march=sapphirerapids -m32 -E -dM %s -o - 2>&1 \
 // RUN:     -target i386-unknown-linux \
 // RUN:   | FileCheck -match-full-lines %s -check-prefix=CHECK_SPR_M32
 // CHECK_SPR_M32: #define __AES__ 1
-// CHECK_SPR_M32: #define __AMXBF16__ 1
-// CHECK_SPR_M32: #define __AMXINT8__ 1
-// CHECK_SPR_M32: #define __AMXTILE__ 1
 // CHECK_SPR_M32: #define __AVX2__ 1
 // CHECK_SPR_M32: #define __AVX512BF16__ 1
 // CHECK_SPR_M32: #define __AVX512BITALG__ 1
 // CHECK_SPR_M32: #define __AVX512BW__ 1
 // CHECK_SPR_M32: #define __AVX512CD__ 1
 // CHECK_SPR_M32: #define __AVX512DQ__ 1
 // CHECK_SPR_M32: #define __AVX512FP16__ 1
 // CHECK_SPR_M32: #define __AVX512F__ 1

 // CHECK_SPR_M32: #define __corei7 1
 // CHECK_SPR_M32: #define __corei7__ 1
 // CHECK_SPR_M32: #define __i386 1
 // CHECK_SPR_M32: #define __i386__ 1
 // CHECK_SPR_M32: #define __tune_corei7__ 1
 // CHECK_SPR_M32: #define i386 1
 
 // RUN: %clang -march=sapphirerapids -m64 -E -dM %s -o - 2>&1 \
-// RUN:     -target i386-unknown-linux \
+// RUN:     -target x86_64-unknown-linux \
 // RUN:   | FileCheck -match-full-lines %s -check-prefix=CHECK_SPR_M64
 // CHECK_SPR_M64: #define __AES__ 1
 // CHECK_SPR_M64: #define __AMXBF16__ 1
 // CHECK_SPR_M64: #define __AMXINT8__ 1
 // CHECK_SPR_M64: #define __AMXTILE__ 1
 // CHECK_SPR_M64: #define __AVX2__ 1
 // CHECK_SPR_M64: #define __AVX512BF16__ 1
 // CHECK_SPR_M64: #define __AVX512BITALG__ 1

clang/test/Preprocessor/x86_amx_target_features.c

-// RUN: %clang -target i386-unknown-linux-gnu -march=i386 -mamx-tile -x c -E -dM -o - %s | FileCheck  -check-prefix=AMX-TILE %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -march=x86-64 -mamx-tile -x c -E -dM -o - %s | FileCheck  -check-prefix=AMX-TILE %s
 
 // AMX-TILE: #define __AMXTILE__ 1
 
-// RUN: %clang -target i386-unknown-linux-gnu -march=i386 -mamx-bf16 -x c -E -dM -o - %s | FileCheck -check-prefix=AMX-BF16 %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -march=x86-64 -mamx-bf16 -x c -E -dM -o - %s | FileCheck -check-prefix=AMX-BF16 %s
 
 // AMX-BF16: #define __AMXBF16__ 1
 // AMX-BF16: #define __AMXTILE__ 1
 
-// RUN: %clang -target i386-unknown-linux-gnu -march=i386 -mamx-int8 -x c -E -dM -o - %s | FileCheck -check-prefix=AMX-INT8 %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -march=x86-64 -mamx-int8 -x c -E -dM -o - %s | FileCheck -check-prefix=AMX-INT8 %s
 
 // AMX-INT8: #define __AMXINT8__ 1
 // AMX-INT8: #define __AMXTILE__ 1
 
-// RUN: %clang -target i386-unknown-linux-gnu -march=i386 -mno-amx-tile -x c -E -dM -o - %s | FileCheck  -check-prefix=NOAMX-TILE %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -march=x86-64 -mno-amx-tile -x c -E -dM -o - %s | FileCheck  -check-prefix=NOAMX-TILE %s
 
 // NOAMX-TILE-NOT: #define __AMXTILE__ 1
 
-// RUN: %clang -target i386-unknown-linux-gnu -march=i386 -mno-amx-bf16 -x c -E -dM -o - %s | FileCheck  -check-prefix=NOAMX-BF16 %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -march=x86-64 -mno-amx-bf16 -x c -E -dM -o - %s | FileCheck  -check-prefix=NOAMX-BF16 %s
 
 // NOAMX-BF16-NOT: #define __AMXBF16__ 1
 
-// RUN: %clang -target i386-unknown-linux-gnu -march=i386 -amx-bf16 -mno-amx-tile -x c -E -dM -o - %s | FileCheck  -check-prefix=NOAMX-BF16 %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -march=x86-64 -amx-bf16 -mno-amx-tile -x c -E -dM -o - %s | FileCheck  -check-prefix=NOAMX-BF16 %s
 
 // NOAMX-BF16-NOT: #define __AMXTILE__ 1
 // NOAMX-BF16-NOT: #define __AMXBF16__ 1
 
-// RUN: %clang -target i386-unknown-linux-gnu -march=i386 -mno-amx-int8 -x c -E -dM -o - %s | FileCheck  -check-prefix=NOAMX-INT8 %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -march=x86-64 -mno-amx-int8 -x c -E -dM -o - %s | FileCheck  -check-prefix=NOAMX-INT8 %s
 
 // NOAMX-INT8-NOT: #define __AMXINT8__ 1
 
-// RUN: %clang -target i386-unknown-linux-gnu -march=i386 -amx-int8 -mno-amx-tile -x c -E -dM -o - %s | FileCheck  -check-prefix=NOAMX-INT8 %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -march=x86-64 -amx-int8 -mno-amx-tile -x c -E -dM -o - %s | FileCheck  -check-prefix=NOAMX-INT8 %s
 
 // NOAMX-INT8-NOT: #define __AMXTILE__ 1
 // NOAMX-INT8-NOT: #define __AMXINT8__ 1