[Qemu-devel] [PATCH] tcg: Fix tcg_reg_alloc_mov vs no-op truncation

[Richard Henderson <rth@twiddle.net>]

Commit af3cbfbe8018ccc16fb3a0048e928f66f0d05e87 hoisted some "common"
loads of the temporary type, forgetting that the types could differ
during truncating moves.  This affects the correctness of the memory
offset on big-endian hosts.

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 tcg/tcg.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/tcg/tcg.c b/tcg/tcg.c
index 0670aff..ea8aa70 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -2096,12 +2096,15 @@ static void tcg_reg_alloc_mov(TCGContext *s, const TCGOpDef *def,
 {
     TCGRegSet allocated_regs;
     TCGTemp *ts, *ots;
-    TCGType type;
+    TCGType otype, itype;
 
     tcg_regset_set(allocated_regs, s->reserved_regs);
     ots = &s->temps[args[0]];
     ts = &s->temps[args[1]];
-    type = ots->type;
+
+    /* Note that otype != itype for no-op truncation.  */
+    otype = ots->type;
+    itype = ts->type;
 
     /* If the source value is not in a register, and we're going to be
        forced to have it in a register in order to perform the copy,
@@ -2109,13 +2112,13 @@ static void tcg_reg_alloc_mov(TCGContext *s, const TCGOpDef *def,
        we don't have to reload SOURCE the next time it is used. */
     if (((NEED_SYNC_ARG(0) || ots->fixed_reg) && ts->val_type != TEMP_VAL_REG)
         || ts->val_type == TEMP_VAL_MEM) {
-        ts->reg = tcg_reg_alloc(s, tcg_target_available_regs[type],
+        ts->reg = tcg_reg_alloc(s, tcg_target_available_regs[itype],
                                 allocated_regs);
         if (ts->val_type == TEMP_VAL_MEM) {
-            tcg_out_ld(s, type, ts->reg, ts->mem_reg, ts->mem_offset);
+            tcg_out_ld(s, itype, ts->reg, ts->mem_reg, ts->mem_offset);
             ts->mem_coherent = 1;
         } else if (ts->val_type == TEMP_VAL_CONST) {
-            tcg_out_movi(s, type, ts->reg, ts->val);
+            tcg_out_movi(s, itype, ts->reg, ts->val);
         }
         s->reg_to_temp[ts->reg] = args[1];
         ts->val_type = TEMP_VAL_REG;
@@ -2130,7 +2133,7 @@ static void tcg_reg_alloc_mov(TCGContext *s, const TCGOpDef *def,
         if (!ots->mem_allocated) {
             temp_allocate_frame(s, args[0]);
         }
-        tcg_out_st(s, type, ts->reg, ots->mem_reg, ots->mem_offset);
+        tcg_out_st(s, otype, ts->reg, ots->mem_reg, ots->mem_offset);
         if (IS_DEAD_ARG(1)) {
             temp_dead(s, args[1]);
         }
@@ -2158,10 +2161,10 @@ static void tcg_reg_alloc_mov(TCGContext *s, const TCGOpDef *def,
                 /* When allocating a new register, make sure to not spill the
                    input one. */
                 tcg_regset_set_reg(allocated_regs, ts->reg);
-                ots->reg = tcg_reg_alloc(s, tcg_target_available_regs[type],
+                ots->reg = tcg_reg_alloc(s, tcg_target_available_regs[otype],
                                          allocated_regs);
             }
-            tcg_out_mov(s, type, ots->reg, ts->reg);
+            tcg_out_mov(s, otype, ots->reg, ts->reg);
         }
         ots->val_type = TEMP_VAL_REG;
         ots->mem_coherent = 0;
-- 
1.9.0