[Qemu-devel] [PATCH] Fix truncate/extend reversal in MIPS DIV{, U} handling

[Richard Sandiford]

The MIPS DIV and DIVU handling has the truncations and extensions
reversed.  This means that, on 64-bit targets, 32-bit results are
not being sign-extended to fill LO and HI.

Richard


Index: qemu/target-mips/translate.c
===================================================================
--- qemu.orig/target-mips/translate.c   2008-05-25 09:57:57.000000000 +0100
+++ qemu/target-mips/translate.c        2008-05-25 09:57:58.000000000 +0100
@@ -1989,12 +1989,12 @@ static void gen_muldiv (DisasContext *ct
                 TCGv r_tmp2 = new_tmp();
                 TCGv r_tmp3 = new_tmp();
 
-                tcg_gen_ext_i32_tl(r_tmp1, cpu_T[0]);
-                tcg_gen_ext_i32_tl(r_tmp2, cpu_T[1]);
+                tcg_gen_trunc_tl_i32(r_tmp1, cpu_T[0]);
+                tcg_gen_trunc_tl_i32(r_tmp2, cpu_T[1]);
                 tcg_gen_div_i32(r_tmp3, r_tmp1, r_tmp2);
                 tcg_gen_rem_i32(r_tmp1, r_tmp1, r_tmp2);
-                tcg_gen_trunc_tl_i32(cpu_T[0], r_tmp3);
-                tcg_gen_trunc_tl_i32(cpu_T[1], r_tmp1);
+                tcg_gen_ext_i32_tl(cpu_T[0], r_tmp3);
+                tcg_gen_ext_i32_tl(cpu_T[1], r_tmp1);
                 gen_store_LO(cpu_T[0], 0);
                 gen_store_HI(cpu_T[1], 0);
                 dead_tmp(r_tmp1);
@@ -2015,12 +2015,12 @@ static void gen_muldiv (DisasContext *ct
                 TCGv r_tmp2 = new_tmp();
                 TCGv r_tmp3 = new_tmp();
 
-                tcg_gen_ext_i32_tl(r_tmp1, cpu_T[0]);
-                tcg_gen_ext_i32_tl(r_tmp2, cpu_T[1]);
+                tcg_gen_trunc_tl_i32(r_tmp1, cpu_T[0]);
+                tcg_gen_trunc_tl_i32(r_tmp2, cpu_T[1]);
                 tcg_gen_divu_i32(r_tmp3, r_tmp1, r_tmp2);
                 tcg_gen_remu_i32(r_tmp1, r_tmp1, r_tmp2);
-                tcg_gen_trunc_tl_i32(cpu_T[0], r_tmp3);
-                tcg_gen_trunc_tl_i32(cpu_T[1], r_tmp1);
+                tcg_gen_ext_i32_tl(cpu_T[0], r_tmp3);
+                tcg_gen_ext_i32_tl(cpu_T[1], r_tmp1);
                 gen_store_LO(cpu_T[0], 0);
                 gen_store_HI(cpu_T[1], 0);
                 dead_tmp(r_tmp1);