[X86] Add -mgeneral-regs-only support.

Reviewed By: pengfei

Differential Revision: https://reviews.llvm.org/D103943

clang/include/clang/Driver/Options.td

@@ -3207,8 +3207,8 @@ defm aapcs_bitfield_width : BoolOption<"f", "aapcs-bitfield-width",
             " volatile bit-field width is dictated by the field container type. (ARM only).">>,
   Group<m_arm_Features_Group>;
 
-def mgeneral_regs_only : Flag<["-"], "mgeneral-regs-only">, Group<m_aarch64_Features_Group>,
-  HelpText<"Generate code which only uses the general purpose registers (AArch64 only)">;
+def mgeneral_regs_only : Flag<["-"], "mgeneral-regs-only">, Group<m_Group>,
+  HelpText<"Generate code which only uses the general purpose registers (AArch64/x86 only)">;
 def mfix_cortex_a53_835769 : Flag<["-"], "mfix-cortex-a53-835769">,
   Group<m_aarch64_Features_Group>,
   HelpText<"Workaround Cortex-A53 erratum 835769 (AArch64 only)">;

clang/lib/Basic/Targets/X86.cpp

@@ -117,7 +117,20 @@ bool X86TargetInfo::initFeatureMap(
   for (auto &F : CPUFeatures)
     setFeatureEnabled(Features, F, true);
 
-  if (!TargetInfo::initFeatureMap(Features, Diags, CPU, FeaturesVec))
+  std::vector<std::string> UpdatedFeaturesVec;
+  for (const auto &Feature : FeaturesVec) {
+    // Expand general-regs-only to -x86, -mmx and -sse
+    if (Feature == "+general-regs-only") {
+      UpdatedFeaturesVec.push_back("-x87");
+      UpdatedFeaturesVec.push_back("-mmx");
+      UpdatedFeaturesVec.push_back("-sse");
+      continue;
+    }
+
+    UpdatedFeaturesVec.push_back(Feature);
+  }
+
+  if (!TargetInfo::initFeatureMap(Features, Diags, CPU, UpdatedFeaturesVec))
     return false;
 
   // Can't do this earlier because we need to be able to explicitly enable
@@ -126,20 +139,20 @@ bool X86TargetInfo::initFeatureMap(
   // Enable popcnt if sse4.2 is enabled and popcnt is not explicitly disabled.
   auto I = Features.find("sse4.2");
   if (I != Features.end() && I->getValue() &&
-      llvm::find(FeaturesVec, "-popcnt") == FeaturesVec.end())
+      llvm::find(UpdatedFeaturesVec, "-popcnt") == UpdatedFeaturesVec.end())
     Features["popcnt"] = true;
 
   // Additionally, if SSE is enabled and mmx is not explicitly disabled,
   // then enable MMX.
   I = Features.find("sse");
   if (I != Features.end() && I->getValue() &&
-      llvm::find(FeaturesVec, "-mmx") == FeaturesVec.end())
+      llvm::find(UpdatedFeaturesVec, "-mmx") == UpdatedFeaturesVec.end())
     Features["mmx"] = true;
 
   // Enable xsave if avx is enabled and xsave is not explicitly disabled.
   I = Features.find("avx");
   if (I != Features.end() && I->getValue() &&
-      llvm::find(FeaturesVec, "-xsave") == FeaturesVec.end())
+      llvm::find(UpdatedFeaturesVec, "-xsave") == UpdatedFeaturesVec.end())
     Features["xsave"] = true;
 
   return true;
@@ -866,6 +879,7 @@ bool X86TargetInfo::isValidFeatureName(StringRef Name) const {
       .Case("fma4", true)
       .Case("fsgsbase", true)
       .Case("fxsr", true)
+      .Case("general-regs-only", true)
       .Case("gfni", true)
       .Case("hreset", true)
       .Case("invpcid", true)

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

@@ -213,5 +213,24 @@ void x86::getX86TargetFeatures(const Driver &D, const llvm::Triple &Triple,
 
   // Now add any that the user explicitly requested on the command line,
   // which may override the defaults.
-  handleTargetFeaturesGroup(Args, Features, options::OPT_m_x86_Features_Group);
+  for (const Arg *A : Args.filtered(options::OPT_m_x86_Features_Group,
+                                    options::OPT_mgeneral_regs_only)) {
+    StringRef Name = A->getOption().getName();
+    A->claim();
+
+    // Skip over "-m".
+    assert(Name.startswith("m") && "Invalid feature name.");
+    Name = Name.substr(1);
+
+    // Replace -mgeneral-regs-only with -x87, -mmx, -sse
+    if (A->getOption().getID() == options::OPT_mgeneral_regs_only) {
+      Features.insert(Features.end(), {"-x87", "-mmx", "-sse"});
+      continue;
+    }
+
+    bool IsNegative = Name.startswith("no-");
+    if (IsNegative)
+      Name = Name.substr(3);
+    Features.push_back(Args.MakeArgString((IsNegative ? "-" : "+") + Name));
+  }
 }

clang/test/CodeGen/attr-target-general-regs-only-x86.c

@@ -0,0 +1,14 @@
+// Test general-regs-only target attribute on x86
+
+// RUN: %clang_cc1 -triple i386-unknown-linux-gnu -emit-llvm %s -o - | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-llvm %s -o - | FileCheck %s
+
+// CHECK: define{{.*}} void @f() [[GPR_ATTRS:#[0-9]+]]
+void __attribute__((target("general-regs-only"))) f() { }
+// CHECK: define{{.*}} void @f_before() [[GPR_ATTRS:#[0-9]+]]
+void __attribute__((target("avx2,general-regs-only"))) f_before() { }
+// CHECK: define{{.*}} void @f_after() [[AVX2_ATTRS:#[0-9]+]]
+void __attribute__((target("general-regs-only,avx2"))) f_after() { }
+
+// CHECK: attributes [[GPR_ATTRS]] = { {{.*}} "target-features"="{{.*}}-avx{{.*}}-avx2{{.*}}-avx512f{{.*}}-sse{{.*}}-sse2{{.*}}-ssse3{{.*}}-x87{{.*}}"
+// CHECK: attributes [[AVX2_ATTRS]] = { {{.*}} "target-features"="{{.*}}+avx{{.*}}+avx2{{.*}}+sse{{.*}}+sse2{{.*}}+ssse3{{.*}}-avx512f{{.*}}-x87{{.*}}"

clang/test/Driver/x86-mgeneral-regs-only.c

@@ -0,0 +1,26 @@
+// Test the -mgeneral-regs-only option on x86
+
+// RUN: %clang -target i386-unknown-linux-gnu -mgeneral-regs-only %s -### 2>&1 | FileCheck --check-prefix=CMD %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -mgeneral-regs-only %s -### 2>&1 | FileCheck --check-prefix=CMD %s
+// RUN: %clang -target i386-unknown-linux-gnu -mavx2 -mgeneral-regs-only %s -### 2>&1 | FileCheck --check-prefixes=CMD,CMD-BEFORE %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -mavx2 -mgeneral-regs-only %s -### 2>&1 | FileCheck --check-prefixes=CMD,CMD-BEFORE %s
+// RUN: %clang -target i386-unknown-linux-gnu -mgeneral-regs-only -mavx2 %s -### 2>&1 | FileCheck --check-prefixes=CMD,CMD-AFTER %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -mgeneral-regs-only -mavx2 %s -### 2>&1 | FileCheck --check-prefixes=CMD,CMD-AFTER %s
+
+// RUN: %clang -target i386-unknown-linux-gnu -mgeneral-regs-only -S -emit-llvm %s -o - 2>&1 | FileCheck --check-prefix=IR-GPR %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -mgeneral-regs-only -S -emit-llvm %s -o - 2>&1 | FileCheck --check-prefix=IR-GPR %s
+// RUN: %clang -target i386-unknown-linux-gnu -mavx2 -mgeneral-regs-only -S -emit-llvm %s -o - 2>&1 | FileCheck --check-prefix=IR-GPR %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -mavx2 -mgeneral-regs-only -S -emit-llvm %s -o - 2>&1 | FileCheck --check-prefix=IR-GPR %s
+// RUN: %clang -target i386-unknown-linux-gnu -mgeneral-regs-only -mavx2 -S -emit-llvm %s -o - 2>&1 | FileCheck --check-prefix=IR-AVX2 %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -mgeneral-regs-only -mavx2 -S -emit-llvm %s -o - 2>&1 | FileCheck --check-prefix=IR-AVX2 %s
+
+// CMD-BEFORE: "-target-feature" "+avx2"
+// CMD: "-target-feature" "-x87"
+// CMD: "-target-feature" "-mmx"
+// CMD: "-target-feature" "-sse"
+// CMD-AFTER: "-target-feature" "+avx2"
+
+void foo() { }
+
+// IR-GPR: attributes {{.*}} = { {{.*}} "target-features"="{{.*}}-avx{{.*}}-avx2{{.*}}-avx512f{{.*}}-sse{{.*}}-sse2{{.*}}-ssse3{{.*}}-x87{{.*}}"
+// IR-AVX2: attributes {{.*}} = { {{.*}} "target-features"="{{.*}}+avx{{.*}}+avx2{{.*}}+sse{{.*}}+sse2{{.*}}+ssse3{{.*}}-avx512f{{.*}}-x87{{.*}}"