From e0e62e97dfddb01a6f2e32d2f951c317a7478f9a Mon Sep 17 00:00:00 2001 From: Alex Bradbury Date: Fri, 30 Nov 2018 09:56:54 +0000 Subject: [TargetLowering][RISCV] Introduce isSExtCheaperThanZExt hook and implement for RISC-V DAGTypeLegalizer::PromoteSetCCOperands currently prefers to zero-extend operands when it is able to do so. For some targets this is more expensive than a sign-extension, which is also a valid choice. Introduce the isSExtCheaperThanZExt hook and use it in the new SExtOrZExtPromotedInteger helper. On RISC-V, we prefer sign-extension for FromTy == MVT::i32 and ToTy == MVT::i64, as it can be performed using a single instruction. Differential Revision: https://reviews.llvm.org/D52978 llvm-svn: 347977 --- llvm/lib/Target/RISCV/RISCVISelLowering.cpp | 4 ++++ llvm/lib/Target/RISCV/RISCVISelLowering.h | 1 + 2 files changed, 5 insertions(+) (limited to 'llvm/lib/Target') diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp index d8c63a4020f..15fd29e8f45 100644 --- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp +++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp @@ -267,6 +267,10 @@ bool RISCVTargetLowering::isZExtFree(SDValue Val, EVT VT2) const { return TargetLowering::isZExtFree(Val, VT2); } +bool RISCVTargetLowering::isSExtCheaperThanZExt(EVT SrcVT, EVT DstVT) const { + return Subtarget.is64Bit() && SrcVT == MVT::i32 && DstVT == MVT::i64; +} + // Changes the condition code and swaps operands if necessary, so the SetCC // operation matches one of the comparisons supported directly in the RISC-V // ISA. diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.h b/llvm/lib/Target/RISCV/RISCVISelLowering.h index a99e2c2f53b..6970900bb06 100644 --- a/llvm/lib/Target/RISCV/RISCVISelLowering.h +++ b/llvm/lib/Target/RISCV/RISCVISelLowering.h @@ -54,6 +54,7 @@ public: bool isTruncateFree(Type *SrcTy, Type *DstTy) const override; bool isTruncateFree(EVT SrcVT, EVT DstVT) const override; bool isZExtFree(SDValue Val, EVT VT2) const override; + bool isSExtCheaperThanZExt(EVT SrcVT, EVT DstVT) const override; // Provide custom lowering hooks for some operations. SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override; -- cgit v1.2.3