[RISCV] Don't exlude the frame pointer from the callee saved registers in RISCVRegisterInfo::needsFrameBaseReg.

Instead of using getReservedRegs, just check the subtarget reserved
list. getReservedRegs considers the frame pointer to be reserved when
it is being used, but we do need to save/restore it so it should be
counted as a callee saved register. AArch64 hardcodes their callee
saved size, but the comment mentions the Frame Pointer being counted.

Author: topperc

llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp

@@ -609,13 +609,13 @@ bool RISCVRegisterInfo::needsFrameBaseReg(MachineInstr *MI,
   const MachineRegisterInfo &MRI = MF.getRegInfo();
 
   if (TFI->hasFP(MF) && !shouldRealignStack(MF)) {
+    auto &Subtarget = MF.getSubtarget<RISCVSubtarget>();
     // Estimate the stack size used to store callee saved registers(
     // excludes reserved registers).
     unsigned CalleeSavedSize = 0;
-    BitVector ReservedRegs = getReservedRegs(MF);
     for (const MCPhysReg *R = MRI.getCalleeSavedRegs(); MCPhysReg Reg = *R;
          ++R) {
-      if (!ReservedRegs.test(Reg))
+      if (!Subtarget.isRegisterReservedByUser(Reg))
         CalleeSavedSize += getSpillSize(*getMinimalPhysRegClass(Reg));
     }
 

llvm/test/CodeGen/RISCV/local-stack-slot-allocation.ll

@@ -111,3 +111,50 @@ define void @load_with_offset2() {
   store volatile i8 %load, ptr %va_gep, align 4
   ret void
 }
+
+define void @frame_pointer() "frame-pointer"="all" {
+; RV32I-LABEL: frame_pointer:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    addi sp, sp, -2032
+; RV32I-NEXT:    .cfi_def_cfa_offset 2032
+; RV32I-NEXT:    sw ra, 2028(sp) # 4-byte Folded Spill
+; RV32I-NEXT:    sw s0, 2024(sp) # 4-byte Folded Spill
+; RV32I-NEXT:    .cfi_offset ra, -4
+; RV32I-NEXT:    .cfi_offset s0, -8
+; RV32I-NEXT:    addi s0, sp, 2032
+; RV32I-NEXT:    .cfi_def_cfa s0, 0
+; RV32I-NEXT:    addi sp, sp, -480
+; RV32I-NEXT:    lbu a0, -1960(s0)
+; RV32I-NEXT:    sb a0, -1960(s0)
+; RV32I-NEXT:    addi sp, sp, 480
+; RV32I-NEXT:    lw ra, 2028(sp) # 4-byte Folded Reload
+; RV32I-NEXT:    lw s0, 2024(sp) # 4-byte Folded Reload
+; RV32I-NEXT:    addi sp, sp, 2032
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: frame_pointer:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    addi sp, sp, -2032
+; RV64I-NEXT:    .cfi_def_cfa_offset 2032
+; RV64I-NEXT:    sd ra, 2024(sp) # 8-byte Folded Spill
+; RV64I-NEXT:    sd s0, 2016(sp) # 8-byte Folded Spill
+; RV64I-NEXT:    .cfi_offset ra, -8
+; RV64I-NEXT:    .cfi_offset s0, -16
+; RV64I-NEXT:    addi s0, sp, 2032
+; RV64I-NEXT:    .cfi_def_cfa s0, 0
+; RV64I-NEXT:    addi sp, sp, -496
+; RV64I-NEXT:    addi a0, s0, -1972
+; RV64I-NEXT:    lbu a1, 0(a0)
+; RV64I-NEXT:    sb a1, 0(a0)
+; RV64I-NEXT:    addi sp, sp, 496
+; RV64I-NEXT:    ld ra, 2024(sp) # 8-byte Folded Reload
+; RV64I-NEXT:    ld s0, 2016(sp) # 8-byte Folded Reload
+; RV64I-NEXT:    addi sp, sp, 2032
+; RV64I-NEXT:    ret
+
+  %va = alloca [2500 x i8], align 4
+  %va_gep = getelementptr [2000 x i8], ptr %va, i64 0, i64 552
+  %load = load volatile i8, ptr %va_gep, align 4
+  store volatile i8 %load, ptr %va_gep, align 4
+  ret void
+}