[RISCV][NFC] Make logic in RISCVMCCodeEmitter::getImmOpValue more defensive

asb · asb · commit 8d8d0a733f2c · 2018-02-22T13:24:25.000Z
As pointed out by @sabuasal in a comment on D23568, the logic in  
RISCVMCCodeEmitter::getImmOpValue could be more defensive. Although with the  
current instruction definitions it is always the case that `VK_RISCV_LO` is  
always used with either an I- or S-format instruction, this may not always be  
the case in the future. Add a check to ensure we will get an assertion in  
debug builds if that changes.

llvm-svn: 325775
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCCodeEmitter.cpp
@@ -161,16 +161,24 @@ unsigned RISCVMCCodeEmitter::getImmOpValue(const MCInst &MI, unsigned OpNo,
     case RISCVMCExpr::VK_RISCV_Invalid:
       llvm_unreachable("Unhandled fixup kind!");
     case RISCVMCExpr::VK_RISCV_LO:
-      FixupKind = MIFrm == RISCVII::InstFormatI ? RISCV::fixup_riscv_lo12_i
-                                                : RISCV::fixup_riscv_lo12_s;
+      if (MIFrm == RISCVII::InstFormatI)
+        FixupKind = RISCV::fixup_riscv_lo12_i;
+      else if (MIFrm == RISCVII::InstFormatS)
+        FixupKind = RISCV::fixup_riscv_lo12_s;
+      else
+        llvm_unreachable("VK_RISCV_LO used with unexpected instruction format");
       break;
     case RISCVMCExpr::VK_RISCV_HI:
       FixupKind = RISCV::fixup_riscv_hi20;
       break;
     case RISCVMCExpr::VK_RISCV_PCREL_LO:
-      FixupKind = MIFrm == RISCVII::InstFormatI
-                      ? RISCV::fixup_riscv_pcrel_lo12_i
-                      : RISCV::fixup_riscv_pcrel_lo12_s;
+      if (MIFrm == RISCVII::InstFormatI)
+        FixupKind = RISCV::fixup_riscv_pcrel_lo12_i;
+      else if (MIFrm == RISCVII::InstFormatS)
+        FixupKind = RISCV::fixup_riscv_pcrel_lo12_s;
+      else
+        llvm_unreachable(
+            "VK_RISCV_PCREL_LO used with unexpected instruction format");
       break;
     case RISCVMCExpr::VK_RISCV_PCREL_HI:
       FixupKind = RISCV::fixup_riscv_pcrel_hi20;
