[RISCV] Use sign extend for i32 arguments and returns in makeLibCall on RV64.

[craig.topper]

Summary

As far as I know 32 bits arguments and returns on RV64 are always
sign extended to i64. So I think we should be taking this into
account around libcalls.

[luismarques]

Nice catch, LGTM.
I guess part of the reason why this wasn't noticed before is that many libcalls (e.g. __floatunsisf) produce the same value even if you zero-extend the argument.

llvm/lib/Target/RISCV/RISCVISelLowering.h

 //===-- RISCVISelLowering.h - RISCV DAG Lowering Interface ------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
public:
   getExceptionPointerRegister(const Constant *PersonalityFn) const override;
 
   /// If a physical register, this returns the register that receives the
   /// exception typeid on entry to a landing pad.
   Register
   getExceptionSelectorRegister(const Constant *PersonalityFn) const override;
 
   bool shouldExtendTypeInLibCall(EVT Type) const override;
+  bool shouldSignExtendTypeInLibCall(EVT Type, bool IsSigned) const override;
 
   /// Returns the register with the specified architectural or ABI name. This
   /// method is necessary to lower the llvm.read_register.* and
   /// llvm.write_register.* intrinsics. Allocatable registers must be reserved
   /// with the clang -ffixed-xX flag for access to be allowed.
   Register getRegisterByName(const char *RegName, LLT VT,
                              const MachineFunction &MF) const override;
 

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

 //===-- RISCVISelLowering.cpp - RISCV DAG Lowering Implementation  --------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
bool RISCVTargetLowering::shouldExtendTypeInLibCall(EVT Type) const {
   // arguments or return value is f32 type for LP64 ABI.
   RISCVABI::ABI ABI = Subtarget.getTargetABI();
   if (ABI == RISCVABI::ABI_LP64 && (Type == MVT::f32))
     return false;
 
   return true;
 }
 
+bool RISCVTargetLowering::shouldSignExtendTypeInLibCall(EVT Type, bool IsSigned) const {
+  if (Subtarget.is64Bit() && Type == MVT::i32)
+    return true;
+
+  return IsSigned;
+}
+
 bool RISCVTargetLowering::decomposeMulByConstant(LLVMContext &Context, EVT VT,
                                                  SDValue C) const {
   // Check integral scalar types.
   if (VT.isScalarInteger()) {
     // Omit the optimization if the sub target has the M extension and the data
     // size exceeds XLen.
     if (Subtarget.hasStdExtM() && VT.getSizeInBits() > Subtarget.getXLen())
       return false;

llvm/test/CodeGen/RISCV/rv64i-single-softfloat.ll

 }
 
 define i32 @flt_s(float %a, float %b) nounwind {
 ; RV64I-LABEL: flt_s:
 ; RV64I:       # %bb.0:
 ; RV64I-NEXT:    addi sp, sp, -16
 ; RV64I-NEXT:    sd ra, 8(sp) # 8-byte Folded Spill
 ; RV64I-NEXT:    call __ltsf2@plt
-; RV64I-NEXT:    sext.w a0, a0
 ; RV64I-NEXT:    slti a0, a0, 0
 ; RV64I-NEXT:    ld ra, 8(sp) # 8-byte Folded Reload
 ; RV64I-NEXT:    addi sp, sp, 16
 ; RV64I-NEXT:    ret
   %1 = fcmp olt float %a, %b
   %2 = zext i1 %1 to i32
   ret i32 %2
 }
 
 define i32 @fle_s(float %a, float %b) nounwind {
 ; RV64I-LABEL: fle_s:
 ; RV64I:       # %bb.0:
 ; RV64I-NEXT:    addi sp, sp, -16
 ; RV64I-NEXT:    sd ra, 8(sp) # 8-byte Folded Spill
 ; RV64I-NEXT:    call __lesf2@plt
-; RV64I-NEXT:    sext.w a0, a0
 ; RV64I-NEXT:    slti a0, a0, 1
 ; RV64I-NEXT:    ld ra, 8(sp) # 8-byte Folded Reload
 ; RV64I-NEXT:    addi sp, sp, 16
 ; RV64I-NEXT:    ret
   %1 = fcmp ole float %a, %b
   %2 = zext i1 %1 to i32
   ret i32 %2
 }
 
 define i32 @fcmp_ogt(float %a, float %b) nounwind {
 ; RV64I-LABEL: fcmp_ogt:
 ; RV64I:       # %bb.0:
 ; RV64I-NEXT:    addi sp, sp, -16
 ; RV64I-NEXT:    sd ra, 8(sp) # 8-byte Folded Spill
 ; RV64I-NEXT:    call __gtsf2@plt
-; RV64I-NEXT:    sext.w a0, a0
 ; RV64I-NEXT:    sgtz a0, a0
 ; RV64I-NEXT:    ld ra, 8(sp) # 8-byte Folded Reload
 ; RV64I-NEXT:    addi sp, sp, 16
 ; RV64I-NEXT:    ret
   %1 = fcmp ogt float %a, %b
   %2 = zext i1 %1 to i32
   ret i32 %2
 }
 
 define i32 @fcmp_oge(float %a, float %b) nounwind {
 ; RV64I-LABEL: fcmp_oge:
 ; RV64I:       # %bb.0:
 ; RV64I-NEXT:    addi sp, sp, -16
 ; RV64I-NEXT:    sd ra, 8(sp) # 8-byte Folded Spill
 ; RV64I-NEXT:    call __gesf2@plt
-; RV64I-NEXT:    sext.w a0, a0
 ; RV64I-NEXT:    addi a1, zero, -1
 ; RV64I-NEXT:    slt a0, a1, a0
 ; RV64I-NEXT:    ld ra, 8(sp) # 8-byte Folded Reload
 ; RV64I-NEXT:    addi sp, sp, 16
 ; RV64I-NEXT:    ret
   %1 = fcmp oge float %a, %b
   %2 = zext i1 %1 to i32
   ret i32 %2
; RV64I-NEXT:    ret
   ret float %1
 }
 
 define float @fcvt_s_wu(i32 %a) nounwind {
 ; RV64I-LABEL: fcvt_s_wu:
 ; RV64I:       # %bb.0:
 ; RV64I-NEXT:    addi sp, sp, -16
 ; RV64I-NEXT:    sd ra, 8(sp) # 8-byte Folded Spill
-; RV64I-NEXT:    slli a0, a0, 32
-; RV64I-NEXT:    srli a0, a0, 32
+; RV64I-NEXT:    sext.w a0, a0
 ; RV64I-NEXT:    call __floatunsisf@plt
 ; RV64I-NEXT:    ld ra, 8(sp) # 8-byte Folded Reload
 ; RV64I-NEXT:    addi sp, sp, 16
 ; RV64I-NEXT:    ret
   %1 = uitofp i32 %a to float
   ret float %1
 }
 

 
 declare float @llvm.powi.f32(float %Val, i32 %power)
 
 define float @fpowi_s(float %a, i32 %b) nounwind {
 ; RV64I-LABEL: fpowi_s:
 ; RV64I:       # %bb.0:
 ; RV64I-NEXT:    addi sp, sp, -16
 ; RV64I-NEXT:    sd ra, 8(sp) # 8-byte Folded Spill
-; RV64I-NEXT:    slli a1, a1, 32
-; RV64I-NEXT:    srli a1, a1, 32
+; RV64I-NEXT:    sext.w a1, a1
 ; RV64I-NEXT:    call __powisf2@plt
 ; RV64I-NEXT:    ld ra, 8(sp) # 8-byte Folded Reload
 ; RV64I-NEXT:    addi sp, sp, 16
 ; RV64I-NEXT:    ret
   %1 = call float @llvm.powi.f32(float %a, i32 %b)
   ret float %1
 }