[RISCV] Define risc-v's own register class to model FP Register.

The default RegisterClass is not enough to model RISCV Register.
We define risc-v's own register class to model FP Register.
This helps to better estimate the register pressure in the loop-vectorize.

Reviewed By: kito-cheng

Differential Revision: https://reviews.llvm.org/D126854

llvm/lib/Target/RISCV/RISCVTargetTransformInfo.h

@@ -202,18 +202,51 @@ class RISCVTTIImpl : public BasicTTIImplBase<RISCVTTIImpl> {
     return VF == 1 ? 1 : ST->getMaxInterleaveFactor();
   }
 
-  // TODO: We should define RISC-V's own register classes.
-  //       e.g. register class for FPR.
+  enum RISCVRegisterClass { GPRRC, FPRRC, VRRC };
   unsigned getNumberOfRegisters(unsigned ClassID) const {
-    bool Vector = (ClassID == 1);
-    if (Vector) {
-      if (ST->hasVInstructions())
+    switch (ClassID) {
+    case RISCVRegisterClass::GPRRC:
+      // 31 = 32 GPR - x0 (zero register)
+      // FIXME: Should we exclude fixed registers like SP, TP or GP?
+      return 31;
+    case RISCVRegisterClass::FPRRC:
+      if (ST->hasStdExtF())
         return 32;
       return 0;
+    case RISCVRegisterClass::VRRC:
+      // Although there are 32 vector registers, v0 is special in that it is the
+      // only register that can be used to hold a mask.
+      // FIXME: Should we conservatively return 31 as the number of usable
+      // vector registers?
+      return ST->hasVInstructions() ? 32 : 0;
     }
-    // 31 = 32 GPR - x0 (zero register)
-    // FIXME: Should we exclude fixed registers like SP, TP or GP?
-    return 31;
+    llvm_unreachable("unknown register class");
+  }
+  unsigned getRegisterClassForType(bool Vector, Type *Ty = nullptr) const {
+    if (Vector)
+      return RISCVRegisterClass::VRRC;
+    if (!Ty)
+      return RISCVRegisterClass::GPRRC;
+
+    Type *ScalarTy = Ty->getScalarType();
+    if ((ScalarTy->isHalfTy() && ST->hasStdExtZfh()) ||
+        (ScalarTy->isFloatTy() && ST->hasStdExtF()) ||
+        (ScalarTy->isDoubleTy() && ST->hasStdExtD())) {
+      return RISCVRegisterClass::FPRRC;
+    }
+
+    return RISCVRegisterClass::GPRRC;
+  };
+  const char *getRegisterClassName(unsigned ClassID) const {
+    switch (ClassID) {
+    case RISCVRegisterClass::GPRRC:
+      return "RISCV::GPRRC";
+    case RISCVRegisterClass::FPRRC:
+      return "RISCV::FPRRC";
+    case RISCVRegisterClass::VRRC:
+      return "RISCV::VRRC";
+    }
+    llvm_unreachable("unknown register class");
   }
 };
 

llvm/test/Transforms/LoopVectorize/RISCV/reg-usage.ll

@@ -1,6 +1,10 @@
 ; REQUIRES: asserts
 ; RUN: opt -loop-vectorize -mtriple riscv64-linux-gnu \
 ; RUN:   -mattr=+v,+d -debug-only=loop-vectorize \
+; RUN:   -riscv-v-vector-bits-min=128 -force-vector-width=1 \
+; RUN:   -S < %s 2>&1 | FileCheck %s --check-prefix=CHECK-SCALAR
+; RUN: opt -loop-vectorize -mtriple riscv64-linux-gnu \
+; RUN:   -mattr=+v,+d -debug-only=loop-vectorize \
 ; RUN:   -riscv-v-vector-bits-min=128 -riscv-v-register-bit-width-lmul=1 \
 ; RUN:   -S < %s 2>&1 | FileCheck %s --check-prefix=CHECK-LMUL1
 ; RUN: opt -loop-vectorize -mtriple riscv64-linux-gnu \
@@ -18,26 +22,31 @@
 
 define void @add(float* noalias nocapture readonly %src1, float* noalias nocapture readonly %src2, i32 signext %size, float* noalias nocapture writeonly %result) {
 ; CHECK-LABEL: add
-; CHECK-LMUL1:      LV(REG): Found max usage: 2 item
-; CHECK-LMUL1-NEXT: LV(REG): RegisterClass: Generic::ScalarRC, 2 registers
-; CHECK-LMUL1-NEXT: LV(REG): RegisterClass: Generic::VectorRC, 2 registers
-; CHECK-LMUL1-NEXT: LV(REG): Found invariant usage: 1 item
-; CHECK-LMUL1-NEXT: LV(REG): RegisterClass: Generic::VectorRC, 2 registers
-; CHECK-LMUL2:      LV(REG): Found max usage: 2 item
-; CHECK-LMUL2-NEXT: LV(REG): RegisterClass: Generic::ScalarRC, 2 registers
-; CHECK-LMUL2-NEXT: LV(REG): RegisterClass: Generic::VectorRC, 4 registers
-; CHECK-LMUL2-NEXT: LV(REG): Found invariant usage: 1 item
-; CHECK-LMUL2-NEXT: LV(REG): RegisterClass: Generic::VectorRC, 4 registers
-; CHECK-LMUL4:      LV(REG): Found max usage: 2 item
-; CHECK-LMUL4-NEXT: LV(REG): RegisterClass: Generic::ScalarRC, 2 registers
-; CHECK-LMUL4-NEXT: LV(REG): RegisterClass: Generic::VectorRC, 8 registers
-; CHECK-LMUL4-NEXT: LV(REG): Found invariant usage: 1 item
-; CHECK-LMUL4-NEXT: LV(REG): RegisterClass: Generic::VectorRC, 8 registers
-; CHECK-LMUL8:      LV(REG): Found max usage: 2 item
-; CHECK-LMUL8-NEXT: LV(REG): RegisterClass: Generic::ScalarRC, 2 registers
-; CHECK-LMUL8-NEXT: LV(REG): RegisterClass: Generic::VectorRC, 16 registers
-; CHECK-LMUL8-NEXT: LV(REG): Found invariant usage: 1 item
-; CHECK-LMUL8-NEXT: LV(REG): RegisterClass: Generic::VectorRC, 16 registers
+; CHECK-SCALAR:      LV(REG): Found max usage: 2 item
+; CHECK-SCALAR-NEXT: LV(REG): RegisterClass: RISCV::GPRRC, 2 registers
+; CHECK-SCALAR-NEXT: LV(REG): RegisterClass: RISCV::FPRRC, 2 registers
+; CHECK-SCALAR-NEXT: LV(REG): Found invariant usage: 1 item
+; CHECK-SCALAR-NEXT: LV(REG): RegisterClass: RISCV::GPRRC, 1 registers
+; CHECK-LMUL1:       LV(REG): Found max usage: 2 item
+; CHECK-LMUL1-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 2 registers
+; CHECK-LMUL1-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 2 registers
+; CHECK-LMUL1-NEXT:  LV(REG): Found invariant usage: 1 item
+; CHECK-LMUL1-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 2 registers
+; CHECK-LMUL2:       LV(REG): Found max usage: 2 item
+; CHECK-LMUL2-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 2 registers
+; CHECK-LMUL2-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 4 registers
+; CHECK-LMUL2-NEXT:  LV(REG): Found invariant usage: 1 item
+; CHECK-LMUL2-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 4 registers
+; CHECK-LMUL4:       LV(REG): Found max usage: 2 item
+; CHECK-LMUL4-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 2 registers
+; CHECK-LMUL4-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 8 registers
+; CHECK-LMUL4-NEXT:  LV(REG): Found invariant usage: 1 item
+; CHECK-LMUL4-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 8 registers
+; CHECK-LMUL8:       LV(REG): Found max usage: 2 item
+; CHECK-LMUL8-NEXT:  LV(REG): RegisterClass: RISCV::GPRRC, 2 registers
+; CHECK-LMUL8-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 16 registers
+; CHECK-LMUL8-NEXT:  LV(REG): Found invariant usage: 1 item
+; CHECK-LMUL8-NEXT:  LV(REG): RegisterClass: RISCV::VRRC, 16 registers
 
 entry:
   %conv = zext i32 %size to i64