[RISCV] Handle variable sized objects with the stack need to be realigned

Differential Revision: https://reviews.llvm.org/D68979

2 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Target/RISCV/Utils/RISCVBaseInfo.cpp b/llvm/lib/Target/RISCV/Utils/RISCVBaseInfo.cpp
index bc5395768ca..9c54c3749a1 100644
--- a/llvm/lib/Target/RISCV/Utils/RISCVBaseInfo.cpp
+++ b/llvm/lib/Target/RISCV/Utils/RISCVBaseInfo.cpp
@@ -66,6 +66,12 @@ ABI computeTargetABI(const Triple &TT, FeatureBitset FeatureBits,
     return ABI_LP64;
   return ABI_ILP32;
 }
+
+// To avoid the BP value clobbered by a function call, we need to choose a
+// callee saved register to save the value. RV32E only has X8 and X9 as callee
+// saved registers and X8 will be used as fp. So we choose X9 as bp.
+Register getBPReg() { return RISCV::X9; }
+
 } // namespace RISCVABI
 
 namespace RISCVFeatures {
diff --git a/llvm/lib/Target/RISCV/Utils/RISCVBaseInfo.h b/llvm/lib/Target/RISCV/Utils/RISCVBaseInfo.h
index 30e475e80a0..738f635ada9 100644
--- a/llvm/lib/Target/RISCV/Utils/RISCVBaseInfo.h
+++ b/llvm/lib/Target/RISCV/Utils/RISCVBaseInfo.h
@@ -13,6 +13,7 @@
 #ifndef LLVM_LIB_TARGET_RISCV_MCTARGETDESC_RISCVBASEINFO_H
 #define LLVM_LIB_TARGET_RISCV_MCTARGETDESC_RISCVBASEINFO_H
 
+#include "RISCVRegisterInfo.h"
 #include "MCTargetDesc/RISCVMCTargetDesc.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSwitch.h"
@@ -195,6 +196,9 @@ enum ABI {
 ABI computeTargetABI(const Triple &TT, FeatureBitset FeatureBits,
                      StringRef ABIName);
 
+// Returns the register used to hold the stack pointer after realignment.
+Register getBPReg();
+
 } // namespace RISCVABI
 
 namespace RISCVFeatures {