RFR: 8287552: riscv: Fix comment typo in li64

[Feilong Jiang]

In riscv, 'imm[31:28]’ should be 'imm[31:20]' for '0x7ff' in the following two places:

src/hotspot/cpu/riscv/assembler_riscv.cpp:


void Assembler::li64(Register Rd, int64_t imm) {
// Load upper 32 bits. upper = imm[63:32], but if imm[31] == 1 or
// (imm[31:28] == 0x7ff && imm[19] == 1), upper = imm[63:32] + 1.
int64_t lower = imm & 0xffffffff;


src/hotspot/cpu/riscv/macroAssembler_riscv.cpp:


  // Load upper 32 bits. Upper = target[63:32], but if target[31] = 1 or (target[31:28] == 0x7ff && target[19] == 1),
  // upper = target[63:32] + 1.


This patch also unifies the immediate type in `movptr_with_offset` to `int64_t`.

Hotspot tier1 test on QEMU passed without new failures.

-------------

Commit messages:
 - fix typo

Changes: https://git.openjdk.java.net/jdk/pull/8950/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8950&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287552
  Stats: 5 lines in 2 files changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8950.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8950/head:pull/8950

PR: https://git.openjdk.java.net/jdk/pull/8950