CSKY: Consume "float-abi" module flag (#212975)

Start respecting float-abi, and fall back on the TargetOptions
field if not present.

Co-authored-by: Claude (Claude-Opus-4.8) <noreply@anthropic.com>

llvm/lib/Target/CSKY/CSKY.td

@@ -14,9 +14,6 @@ include "llvm/Target/Target.td"
 def ModeHardFloat :
   SubtargetFeature<"hard-float", "UseHardFloat",
                    "true", "Use hard floating point features">;
-def ModeHardFloatABI :
-  SubtargetFeature<"hard-float-abi", "UseHardFloatABI",
-                   "true", "Use hard floating point ABI to pass args">;
 
 def FeatureFPUV2_SF
     : SubtargetFeature<"fpuv2_sf", "HasFPUv2SingleFloat", "true",

llvm/lib/Target/CSKY/CSKYAsmPrinter.cpp

@@ -23,6 +23,7 @@
 #include "llvm/CodeGen/MachineConstantPool.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Module.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCInstBuilder.h"
@@ -129,7 +130,7 @@ void CSKYAsmPrinter::emitFunctionBodyEnd() {
 
 void CSKYAsmPrinter::emitStartOfAsmFile(Module &M) {
   if (TM.getTargetTriple().isOSBinFormatELF())
-    emitAttributes();
+    emitAttributes(M);
 }
 
 void CSKYAsmPrinter::emitEndOfAsmFile(Module &M) {
@@ -245,11 +246,12 @@ void CSKYAsmPrinter::emitMachineConstantPoolValue(
   OutStreamer->emitValue(Expr, Size);
 }
 
-void CSKYAsmPrinter::emitAttributes() {
+void CSKYAsmPrinter::emitAttributes(Module &M) {
   CSKYTargetStreamer &CTS =
       static_cast<CSKYTargetStreamer &>(*OutStreamer->getTargetStreamer());
 
-  CTS.emitTargetAttributes(TM.getMCSubtargetInfo());
+  CTS.emitTargetAttributes(TM.getMCSubtargetInfo(),
+                           M.getFloatABI() == FloatABI::Hard);
 }
 
 bool CSKYAsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,

llvm/lib/Target/CSKY/CSKYAsmPrinter.h

@@ -29,7 +29,7 @@ class LLVM_LIBRARY_VISIBILITY CSKYAsmPrinter : public AsmPrinter {
 
   void expandTLSLA(const MachineInstr *MI);
   void emitCustomConstantPool(const MachineInstr *MI);
-  void emitAttributes();
+  void emitAttributes(Module &M);
 
 public:
   explicit CSKYAsmPrinter(TargetMachine &TM,

llvm/lib/Target/CSKY/CSKYSubtarget.cpp

@@ -89,10 +89,12 @@ CSKYSubtarget &CSKYSubtarget::initializeSubtargetDependencies(
 }
 
 CSKYSubtarget::CSKYSubtarget(const Triple &TT, StringRef CPU, StringRef TuneCPU,
-                             StringRef FS, const TargetMachine &TM)
+                             StringRef FS, FloatABI::ABIType FloatABI,
+                             const TargetMachine &TM)
     : CSKYGenSubtargetInfo(TT, CPU, TuneCPU, FS),
       FrameLowering(initializeSubtargetDependencies(TT, CPU, TuneCPU, FS)),
-      InstrInfo(*this, RegInfo), TLInfo(TM, *this) {
+      InstrInfo(*this, RegInfo), TLInfo(TM, *this),
+      UseHardFloatABI(FloatABI == FloatABI::Hard) {
   TSInfo = std::make_unique<CSKYSelectionDAGInfo>();
 }
 
@@ -101,12 +103,3 @@ CSKYSubtarget::~CSKYSubtarget() = default;
 const SelectionDAGTargetInfo *CSKYSubtarget::getSelectionDAGInfo() const {
   return TSInfo.get();
 }
-
-bool CSKYSubtarget::useHardFloatABI() const {
-  auto FloatABI = getTargetLowering()->getTargetMachine().Options.FloatABIType;
-
-  if (FloatABI == FloatABI::Default)
-    return UseHardFloatABI;
-  else
-    return FloatABI == FloatABI::Hard;
-}

llvm/lib/Target/CSKY/CSKYSubtarget.h

@@ -109,7 +109,8 @@ class CSKYSubtarget : public CSKYGenSubtargetInfo {
 
 public:
   CSKYSubtarget(const Triple &TT, StringRef CPU, StringRef TuneCPU,
-                StringRef FS, const TargetMachine &TM);
+                StringRef FS, FloatABI::ABIType FloatABI,
+                const TargetMachine &TM);
 
   ~CSKYSubtarget() override;
 
@@ -134,7 +135,8 @@ public:
   // Generated by inc file
   void ParseSubtargetFeatures(StringRef CPU, StringRef TuneCPU, StringRef FS);
 
-  bool useHardFloatABI() const;
+  bool useHardFloatABI() const { return UseHardFloatABI; }
+
   bool useHardFloat() const { return UseHardFloat; }
   bool hasFPUv2SingleFloat() const { return HasFPUv2SingleFloat; }
   bool hasFPUv2DoubleFloat() const { return HasFPUv2DoubleFloat; }

llvm/lib/Target/CSKY/CSKYTargetMachine.cpp

@@ -20,6 +20,7 @@
 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
 #include "llvm/CodeGen/TargetPassConfig.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
+#include "llvm/IR/Module.h"
 #include "llvm/MC/TargetRegistry.h"
 #include <optional>
 
@@ -59,10 +60,16 @@ CSKYTargetMachine::getSubtargetImpl(const Function &F) const {
   std::string FS =
       FSAttr.isValid() ? FSAttr.getValueAsString().str() : TargetFS;
 
+  FloatABI::ABIType FloatABI = F.getParent()->getFloatABI();
+  if (FloatABI == FloatABI::Default)
+    FloatABI = Options.FloatABIType;
+
   std::string Key = CPU + TuneCPU + FS;
+  Key += FloatABI == FloatABI::Hard ? "+hard-float-abi" : "+soft-float-abi";
   auto &I = SubtargetMap[Key];
   if (!I) {
-    I = std::make_unique<CSKYSubtarget>(TargetTriple, CPU, TuneCPU, FS, *this);
+    I = std::make_unique<CSKYSubtarget>(TargetTriple, CPU, TuneCPU, FS,
+                                        FloatABI, *this);
     if (I->useHardFloat() && !I->hasAnyFloatExt())
       errs() << "Hard-float can't be used with current CPU,"
                 " set to Soft-float\n";

llvm/lib/Target/CSKY/MCTargetDesc/CSKYELFStreamer.cpp

@@ -177,7 +177,8 @@ void CSKYELFStreamer::EmitMappingSymbol(StringRef Name) {
   Symbol->setBinding(ELF::STB_LOCAL);
 }
 
-void CSKYTargetELFStreamer::emitTargetAttributes(const MCSubtargetInfo &STI) {
+void CSKYTargetELFStreamer::emitTargetAttributes(const MCSubtargetInfo &STI,
+                                                 bool HardFloatABI) {
   StringRef CPU = STI.getCPU();
   CSKY::ArchKind ArchID = CSKY::parseCPUArch(CPU);
 
@@ -309,8 +310,11 @@ void CSKYTargetELFStreamer::emitTargetAttributes(const MCSubtargetInfo &STI) {
                         STI.hasFeature(CSKY::FeatureFPUV3_SF) ||
                         STI.hasFeature(CSKY::FeatureFPUV3_DF);
 
-  if (hasAnyFloatExt && STI.hasFeature(CSKY::ModeHardFloat) &&
-      STI.hasFeature(CSKY::ModeHardFloatABI))
+  // The hard-float *ABI* (FP values in FP registers at call boundaries) is
+  // selected by the "float-abi" module flag, resolved by the caller; it does
+  // not depend on ModeHardFloat, which only distinguishes the soft-float ABI
+  // that still uses hard-float instructions (SOFTFP) from pure soft float.
+  if (hasAnyFloatExt && HardFloatABI)
     emitAttribute(CSKYAttrs::CSKY_FPU_ABI, CSKYAttrs::FPU_ABI_HARD);
   else if (hasAnyFloatExt && STI.hasFeature(CSKY::ModeHardFloat))
     emitAttribute(CSKYAttrs::CSKY_FPU_ABI, CSKYAttrs::FPU_ABI_SOFTFP);

llvm/lib/Target/CSKY/MCTargetDesc/CSKYELFStreamer.h

@@ -91,7 +91,8 @@ private:
   void finishAttributeSection() override;
   size_t calculateContentSize() const;
 
-  void emitTargetAttributes(const MCSubtargetInfo &STI) override;
+  void emitTargetAttributes(const MCSubtargetInfo &STI,
+                            bool HardFloatABI = false) override;
 
 public:
   MCELFStreamer &getStreamer();

llvm/lib/Target/CSKY/MCTargetDesc/CSKYTargetStreamer.cpp

@@ -124,7 +124,8 @@ void CSKYTargetStreamer::finish() {
   finishAttributeSection();
 }
 
-void CSKYTargetStreamer::emitTargetAttributes(const MCSubtargetInfo &STI) {}
+void CSKYTargetStreamer::emitTargetAttributes(const MCSubtargetInfo &STI,
+                                              bool HardFloatABI) {}
 
 void CSKYTargetStreamer::emitAttribute(unsigned Attribute, unsigned Value) {}
 void CSKYTargetStreamer::emitTextAttribute(unsigned Attribute,

llvm/lib/Target/CSKY/MCTargetDesc/CSKYTargetStreamer.h

@@ -64,7 +64,8 @@ public:
   virtual void emitAttribute(unsigned Attribute, unsigned Value);
   virtual void finishAttributeSection();
 
-  virtual void emitTargetAttributes(const MCSubtargetInfo &STI);
+  virtual void emitTargetAttributes(const MCSubtargetInfo &STI,
+                                    bool HardFloatABI = false);
   /// Add a new entry to the constant pool for the current section and return an
   /// MCExpr that can be used to refer to the constant pool location.
   const MCExpr *addConstantPoolEntry(const MCExpr *, SMLoc Loc,

llvm/test/CodeGen/CSKY/float-abi-module-flag.ll

@@ -0,0 +1,45 @@
+; The "float-abi" module flag selects the floating-point calling convention.
+; RUN: split-file %s %t
+
+; Soft float ABI (the target default): FP arguments are passed in GPRs and moved
+; into VFP registers with fmtvrl.
+; RUN: llc -csky-no-aliases -mtriple=csky -mattr=+2e3,+fpuv2_sf,+fpuv2_df,+hard-float < %t/none.ll | FileCheck %s --check-prefix=SOFT
+
+; Hard float ABI module flag: FP arguments arrive directly in VFP registers, so
+; no fmtvrl moves are needed.
+; RUN: llc -csky-no-aliases -mtriple=csky -mattr=+2e3,+fpuv2_sf,+fpuv2_df,+hard-float < %t/hard.ll | FileCheck %s --check-prefix=HARD
+
+; Soft float ABI module flag matches the default.
+; RUN: llc -csky-no-aliases -mtriple=csky -mattr=+2e3,+fpuv2_sf,+fpuv2_df,+hard-float < %t/soft.ll | FileCheck %s --check-prefix=SOFT
+
+; The legacy -float-abi target option still selects the ABI when the module has
+; no "float-abi" flag.
+; RUN: llc -csky-no-aliases -mtriple=csky -mattr=+2e3,+fpuv2_sf,+fpuv2_df,+hard-float -float-abi=hard < %t/none.ll | FileCheck %s --check-prefix=HARD
+
+; An explicit module flag takes precedence over the legacy -float-abi option.
+; RUN: llc -csky-no-aliases -mtriple=csky -mattr=+2e3,+fpuv2_sf,+fpuv2_df,+hard-float -float-abi=hard < %t/soft.ll | FileCheck %s --check-prefix=SOFT
+
+;--- none.ll
+define float @f(float %x, float %y) {
+  %r = fadd float %x, %y
+  ret float %r
+}
+
+;--- hard.ll
+define float @f(float %x, float %y) {
+  %r = fadd float %x, %y
+  ret float %r
+}
+!llvm.module.flags = !{!0}
+!0 = !{i32 1, !"float-abi", !"hard"}
+
+;--- soft.ll
+define float @f(float %x, float %y) {
+  %r = fadd float %x, %y
+  ret float %r
+}
+!llvm.module.flags = !{!0}
+!0 = !{i32 1, !"float-abi", !"soft"}
+
+; SOFT: fmtvrl
+; HARD-NOT: fmtvrl

llvm/test/CodeGen/CSKY/fpu-abi-attribute.ll

@@ -0,0 +1,41 @@
+; The emitted Tag_CSKY_FPU_ABI build attribute (17) reflects the floating-point
+; ABI: hard-float ABI (from the "float-abi" module flag) emits FPU_ABI_HARD (3),
+; while the soft-float ABI with hard-float instructions available emits
+; FPU_ABI_SOFTFP (2), and no float unit emits FPU_ABI_SOFT (1).
+
+; RUN: split-file %s %t
+
+; Hard float ABI module flag with an FPU: FPU_ABI_HARD (3).
+; RUN: llc -mtriple=csky -mattr=+2e3,+fpuv2_sf,+fpuv2_df,+hard-float < %t/hard.ll | FileCheck %s --check-prefix=HARD
+
+; Soft float ABI (target default) with an FPU: FPU_ABI_SOFTFP (2).
+; RUN: llc -mtriple=csky -mattr=+2e3,+fpuv2_sf,+fpuv2_df,+hard-float < %t/none.ll | FileCheck %s --check-prefix=SOFTFP
+
+; Explicit soft float ABI module flag with an FPU: FPU_ABI_SOFTFP (2).
+; RUN: llc -mtriple=csky -mattr=+2e3,+fpuv2_sf,+fpuv2_df,+hard-float < %t/soft.ll | FileCheck %s --check-prefix=SOFTFP
+
+; No float unit: FPU_ABI_SOFT (1), regardless of the module flag.
+; RUN: llc -mtriple=csky -mattr=+2e3 < %t/hard.ll | FileCheck %s --check-prefix=SOFT
+
+; HARD: .csky_attribute 17, 3
+; SOFTFP: .csky_attribute 17, 2
+; SOFT: .csky_attribute 17, 1
+
+;--- none.ll
+define void @f() {
+  ret void
+}
+
+;--- hard.ll
+define void @f() {
+  ret void
+}
+!llvm.module.flags = !{!0}
+!0 = !{i32 1, !"float-abi", !"hard"}
+
+;--- soft.ll
+define void @f() {
+  ret void
+}
+!llvm.module.flags = !{!0}
+!0 = !{i32 1, !"float-abi", !"soft"}