[llvm] [SPIRV] Add FPVariant tracking for floating-point registers in SPIR-V (PR #156871)

[via llvm-commits]

https://github.com/YixingZhang007 updated https://github.com/llvm/llvm-project/pull/156871

>From b1ae15f6fac1675159d8acf003bb4b22f4e015e2 Mon Sep 17 00:00:00 2001
From: "Zhang, Yixing" <yixing.zhang at intel.com>
Date: Thu, 4 Sep 2025 05:14:39 -0700
Subject: [PATCH 1/3] add the support for bfloat in SPIRV

---
 llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp | 26 ++++++++++++++++++-
 llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.h   | 13 ++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
index cfe24c84941a9..0f258e03b23c8 100644
--- a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
@@ -1122,7 +1122,19 @@ SPIRVType *SPIRVGlobalRegistry::restOfCreateSPIRVType(
   SPIRVType *SpirvType = createSPIRVType(Ty, MIRBuilder, AccessQual,
                                          ExplicitLayoutRequired, EmitIR);
   TypesInProcessing.erase(Ty);
-  VRegToTypeMap[&MIRBuilder.getMF()][getSPIRVTypeID(SpirvType)] = SpirvType;
+
+  // Record the FPVariant of the floating-point registers in the
+  // VRegFPVariantMap.
+  MachineFunction *MF = &MIRBuilder.getMF();
+  Register TypeReg = getSPIRVTypeID(SpirvType);
+  if (Ty->isFloatingPointTy()) {
+    if (Ty->isBFloatTy()) {
+      VRegFPVariantMap[MF][TypeReg] = FPVariant::BRAIN_FLOAT;
+    } else {
+      VRegFPVariantMap[MF][TypeReg] = FPVariant::IEEE_FLOAT;
+    }
+  }
+  VRegToTypeMap[MF][TypeReg] = SpirvType;
 
   // TODO: We could end up with two SPIR-V types pointing to the same llvm type.
   // Is that a problem?
@@ -2088,3 +2100,15 @@ bool SPIRVGlobalRegistry::hasBlockDecoration(SPIRVType *Type) const {
   }
   return false;
 }
+
+SPIRVGlobalRegistry::FPVariant
+SPIRVGlobalRegistry::getFPVariantForVReg(Register VReg,
+                                         const MachineFunction *MF) {
+  auto t = VRegFPVariantMap.find(MF ? MF : CurMF);
+  if (t != VRegFPVariantMap.end()) {
+    auto tt = t->second.find(VReg);
+    if (tt != t->second.end())
+      return tt->second;
+  }
+  return FPVariant::NONE;
+}
\ No newline at end of file
diff --git a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.h b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.h
index 7ef812828b7cc..1f8c30dc01f7f 100644
--- a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.h
+++ b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.h
@@ -29,6 +29,10 @@ using SPIRVType = const MachineInstr;
 using StructOffsetDecorator = std::function<void(Register)>;
 
 class SPIRVGlobalRegistry : public SPIRVIRMapping {
+public:
+  enum class FPVariant { NONE, IEEE_FLOAT, BRAIN_FLOAT };
+
+private:
   // Registers holding values which have types associated with them.
   // Initialized upon VReg definition in IRTranslator.
   // Do not confuse this with DuplicatesTracker as DT maps Type* to <MF, Reg>
@@ -88,6 +92,11 @@ class SPIRVGlobalRegistry : public SPIRVIRMapping {
   // map of aliasing decorations to aliasing metadata
   std::unordered_map<const MDNode *, MachineInstr *> AliasInstMDMap;
 
+  // Maps floating point Registers to their FPVariant (float type kind), given
+  // the MachineFunction.
+  DenseMap<const MachineFunction *, DenseMap<Register, FPVariant>>
+      VRegFPVariantMap;
+
   // Add a new OpTypeXXX instruction without checking for duplicates.
   SPIRVType *createSPIRVType(const Type *Type, MachineIRBuilder &MIRBuilder,
                              SPIRV::AccessQualifier::AccessQualifier AQ,
@@ -422,6 +431,10 @@ class SPIRVGlobalRegistry : public SPIRVIRMapping {
   // structures referring this instruction.
   void invalidateMachineInstr(MachineInstr *MI);
 
+  // Return the FPVariant of to the given floating-point regiester.
+  FPVariant getFPVariantForVReg(Register VReg,
+                                const MachineFunction *MF = nullptr);
+
 private:
   SPIRVType *getOpTypeBool(MachineIRBuilder &MIRBuilder);
 

>From 6fc5c9a741c1e4d885d022a4539cec6b0110c56b Mon Sep 17 00:00:00 2001
From: "Zhang, Yixing" <yixing.zhang at intel.com>
Date: Thu, 4 Sep 2025 05:56:56 -0700
Subject: [PATCH 2/3] nit

---
 llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
index 0f258e03b23c8..e1bb2b912aa3c 100644
--- a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
@@ -2111,4 +2111,4 @@ SPIRVGlobalRegistry::getFPVariantForVReg(Register VReg,
       return tt->second;
   }
   return FPVariant::NONE;
-}
\ No newline at end of file
+}

>From 1118490d6dfd7e264338949710174ea22dddac00 Mon Sep 17 00:00:00 2001
From: "Zhang, Yixing" <yixing.zhang at intel.com>
Date: Fri, 5 Sep 2025 07:31:11 -0700
Subject: [PATCH 3/3] nit change

---
 llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
index e1bb2b912aa3c..6255ec5546ec7 100644
--- a/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVGlobalRegistry.cpp
@@ -2104,11 +2104,16 @@ bool SPIRVGlobalRegistry::hasBlockDecoration(SPIRVType *Type) const {
 SPIRVGlobalRegistry::FPVariant
 SPIRVGlobalRegistry::getFPVariantForVReg(Register VReg,
                                          const MachineFunction *MF) {
-  auto t = VRegFPVariantMap.find(MF ? MF : CurMF);
-  if (t != VRegFPVariantMap.end()) {
-    auto tt = t->second.find(VReg);
-    if (tt != t->second.end())
-      return tt->second;
+  const MachineFunction *Func = MF ? MF : CurMF;
+  DenseMap<const MachineFunction *, DenseMap<Register, FPVariant>>::const_iterator FuncIt =
+      VRegFPVariantMap.find(Func);
+
+  if (FuncIt != VRegFPVariantMap.end()) {
+    const DenseMap<Register, FPVariant> &VRegMap = FuncIt->second;
+    DenseMap<Register, FPVariant>::const_iterator VRegIt = VRegMap.find(VReg);
+
+    if (VRegIt != VRegMap.end())
+      return VRegIt->second;
   }
   return FPVariant::NONE;
 }