tcg/loongarch64: Implement necessary relocation operations

Signed-off-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20211221054105.178795-8-git@xen0n.name>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tcg/loongarch64/tcg-target.c.inc

@@ -168,3 +168,69 @@ static bool tcg_target_const_match(int64_t val, TCGType type, int ct)
     }
     return false;
 }
+
+/*
+ * Relocations
+ */
+
+/*
+ * Relocation records defined in LoongArch ELF psABI v1.00 is way too
+ * complicated; a whopping stack machine is needed to stuff the fields, at
+ * the very least one SOP_PUSH and one SOP_POP (of the correct format) are
+ * needed.
+ *
+ * Hence, define our own simpler relocation types. Numbers are chosen as to
+ * not collide with potential future additions to the true ELF relocation
+ * type enum.
+ */
+
+/* Field Sk16, shifted right by 2; suitable for conditional jumps */
+#define R_LOONGARCH_BR_SK16     256
+/* Field Sd10k16, shifted right by 2; suitable for B and BL */
+#define R_LOONGARCH_BR_SD10K16  257
+
+static bool reloc_br_sk16(tcg_insn_unit *src_rw, const tcg_insn_unit *target)
+{
+    const tcg_insn_unit *src_rx = tcg_splitwx_to_rx(src_rw);
+    intptr_t offset = (intptr_t)target - (intptr_t)src_rx;
+
+    tcg_debug_assert((offset & 3) == 0);
+    offset >>= 2;
+    if (offset == sextreg(offset, 0, 16)) {
+        *src_rw = deposit64(*src_rw, 10, 16, offset);
+        return true;
+    }
+
+    return false;
+}
+
+static bool reloc_br_sd10k16(tcg_insn_unit *src_rw,
+                             const tcg_insn_unit *target)
+{
+    const tcg_insn_unit *src_rx = tcg_splitwx_to_rx(src_rw);
+    intptr_t offset = (intptr_t)target - (intptr_t)src_rx;
+
+    tcg_debug_assert((offset & 3) == 0);
+    offset >>= 2;
+    if (offset == sextreg(offset, 0, 26)) {
+        *src_rw = deposit64(*src_rw, 0, 10, offset >> 16); /* slot d10 */
+        *src_rw = deposit64(*src_rw, 10, 16, offset); /* slot k16 */
+        return true;
+    }
+
+    return false;
+}
+
+static bool patch_reloc(tcg_insn_unit *code_ptr, int type,
+                        intptr_t value, intptr_t addend)
+{
+    tcg_debug_assert(addend == 0);
+    switch (type) {
+    case R_LOONGARCH_BR_SK16:
+        return reloc_br_sk16(code_ptr, (tcg_insn_unit *)value);
+    case R_LOONGARCH_BR_SD10K16:
+        return reloc_br_sd10k16(code_ptr, (tcg_insn_unit *)value);
+    default:
+        g_assert_not_reached();
+    }
+}