[GXemul-devel] Patch: don't crash on MIPS divide overflow

[Andreas G. <gs...@gs...>]

When emulating the MIPS DIV and DDIV instructions, check for divide
overflow instead of performing the overflowing divide on the host and
crashing the emulator.  This is needed to run recent versions of the
NetBSD test suite on an emulated MIPS system.

--- gxemul.old/work/gxemul-0.6.0.1/src/cpus/cpu_mips_instr.cc	2018-08-08 17:27:19.146417631 +0300
+++ gxemul/work/gxemul-0.6.0.1/src/cpus/cpu_mips_instr.cc	2018-08-08 17:27:27.944250037 +0300
@@ -1262,6 +1262,8 @@
 	int32_t res, rem;
 	if (b == 0)
 		res = 0, rem = a;
+	else if (a == (int32_t)0x80000000U && b == -1)
+		res = 0, rem = 0;
 	else
 		res = a / b, rem = a - b*res;
 	cpu->cd.mips.lo = (int32_t)res;
@@ -1284,6 +1286,8 @@
 	int64_t res, rem;
 	if (b == 0)
 		res = 0;
+	else if (a == (int64_t)0x8000000000000000ULL && b == -1)
+		res = 0;
 	else
 		res = a / b;
 	rem = a - b*res;