[Qemu-devel] [PATCH] target-arm: Fix UNDEF cases in Thumb load/store

[Peter Maydell <peter.maydell@linaro.org>]

Decode of Thumb load/store was merging together the cases of 'bit 11==0'
(reg+reg LSL imm) and 'bit 11==1' (reg+imm). This happens to work for
valid instruction patterns but meant that we would not UNDEF for the
cases the architecture mandates that we must. Make the decode actually
look at bit 11 as well as [10..8] so that we UNDEF in the right places.

This change also removes what was a spurious unreachable 'case 8',
and correctly frees TCG temporaries on the illegal-insn codepaths.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
This patch was mostly prompted by that dodgy 'case 8' which I noted
when doing the preload/hint space patches a month or so ago; I have
finally added support for testing loads and stores to risu, so I
can confirm that this patch doesn't break the non-UNDEF cases.

 target-arm/translate.c |   29 ++++++++++++++++++-----------
 1 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/target-arm/translate.c b/target-arm/translate.c
index 062de5e..0afdbfb 100644
--- a/target-arm/translate.c
+++ b/target-arm/translate.c
@@ -8378,39 +8378,42 @@ static int disas_thumb2_insn(CPUState *env, DisasContext *s, uint16_t insn_hw1)
                 tcg_gen_addi_i32(addr, addr, imm);
             } else {
                 imm = insn & 0xff;
-                switch ((insn >> 8) & 7) {
-                case 0: case 8: /* Shifted Register.  */
+                switch ((insn >> 8) & 0xf) {
+                case 0x0: /* Shifted Register.  */
                     shift = (insn >> 4) & 0xf;
-                    if (shift > 3)
+                    if (shift > 3) {
+                        tcg_temp_free_i32(addr);
                         goto illegal_op;
+                    }
                     tmp = load_reg(s, rm);
                     if (shift)
                         tcg_gen_shli_i32(tmp, tmp, shift);
                     tcg_gen_add_i32(addr, addr, tmp);
                     tcg_temp_free_i32(tmp);
                     break;
-                case 4: /* Negative offset.  */
+                case 0xc: /* Negative offset.  */
                     tcg_gen_addi_i32(addr, addr, -imm);
                     break;
-                case 6: /* User privilege.  */
+                case 0xe: /* User privilege.  */
                     tcg_gen_addi_i32(addr, addr, imm);
                     user = 1;
                     break;
-                case 1: /* Post-decrement.  */
+                case 0x9: /* Post-decrement.  */
                     imm = -imm;
                     /* Fall through.  */
-                case 3: /* Post-increment.  */
+                case 0xb: /* Post-increment.  */
                     postinc = 1;
                     writeback = 1;
                     break;
-                case 5: /* Pre-decrement.  */
+                case 0xd: /* Pre-decrement.  */
                     imm = -imm;
                     /* Fall through.  */
-                case 7: /* Pre-increment.  */
+                case 0xf: /* Pre-increment.  */
                     tcg_gen_addi_i32(addr, addr, imm);
                     writeback = 1;
                     break;
                 default:
+                    tcg_temp_free_i32(addr);
                     goto illegal_op;
                 }
             }
@@ -8423,7 +8426,9 @@ static int disas_thumb2_insn(CPUState *env, DisasContext *s, uint16_t insn_hw1)
             case 1: tmp = gen_ld16u(addr, user); break;
             case 5: tmp = gen_ld16s(addr, user); break;
             case 2: tmp = gen_ld32(addr, user); break;
-            default: goto illegal_op;
+            default:
+                tcg_temp_free_i32(addr);
+                goto illegal_op;
             }
             if (rs == 15) {
                 gen_bx(s, tmp);
@@ -8437,7 +8442,9 @@ static int disas_thumb2_insn(CPUState *env, DisasContext *s, uint16_t insn_hw1)
             case 0: gen_st8(tmp, addr, user); break;
             case 1: gen_st16(tmp, addr, user); break;
             case 2: gen_st32(tmp, addr, user); break;
-            default: goto illegal_op;
+            default:
+                tcg_temp_free_i32(addr);
+                goto illegal_op;
             }
         }
         if (postinc)
-- 
1.7.1