Revert "[RISCV] Simplify getStackAdjBase. NFC (#129281)"

This reverts commit 22965dc.

Author: topperc

llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.h

@@ -629,13 +629,49 @@ inline unsigned encodeRlist(MCRegister EndReg, bool IsRV32E = false) {
 inline static unsigned getStackAdjBase(unsigned RlistVal, bool IsRV64) {
   assert(RlistVal != RLISTENCODE::INVALID_RLIST &&
          "{ra, s0-s10} is not supported, s11 must be included.");
-  unsigned NumRegs = (RlistVal - RLISTENCODE::RA) + 1;
-  // s10 and s11 are saved together.
-  if (RlistVal == RLISTENCODE::RA_S0_S11)
-    ++NumRegs;
-
-  unsigned RegSize = IsRV64 ? 8 : 4;
-  return alignTo(NumRegs * RegSize, 16);
+  if (!IsRV64) {
+    switch (RlistVal) {
+    case RLISTENCODE::RA:
+    case RLISTENCODE::RA_S0:
+    case RLISTENCODE::RA_S0_S1:
+    case RLISTENCODE::RA_S0_S2:
+      return 16;
+    case RLISTENCODE::RA_S0_S3:
+    case RLISTENCODE::RA_S0_S4:
+    case RLISTENCODE::RA_S0_S5:
+    case RLISTENCODE::RA_S0_S6:
+      return 32;
+    case RLISTENCODE::RA_S0_S7:
+    case RLISTENCODE::RA_S0_S8:
+    case RLISTENCODE::RA_S0_S9:
+      return 48;
+    case RLISTENCODE::RA_S0_S11:
+      return 64;
+    }
+  } else {
+    switch (RlistVal) {
+    case RLISTENCODE::RA:
+    case RLISTENCODE::RA_S0:
+      return 16;
+    case RLISTENCODE::RA_S0_S1:
+    case RLISTENCODE::RA_S0_S2:
+      return 32;
+    case RLISTENCODE::RA_S0_S3:
+    case RLISTENCODE::RA_S0_S4:
+      return 48;
+    case RLISTENCODE::RA_S0_S5:
+    case RLISTENCODE::RA_S0_S6:
+      return 64;
+    case RLISTENCODE::RA_S0_S7:
+    case RLISTENCODE::RA_S0_S8:
+      return 80;
+    case RLISTENCODE::RA_S0_S9:
+      return 96;
+    case RLISTENCODE::RA_S0_S11:
+      return 112;
+    }
+  }
+  llvm_unreachable("Unexpected RlistVal");
 }
 
 void printRlist(unsigned SlistEncode, raw_ostream &OS);