From b49c4639d1d0dfc0a5954cda465dd3375c2d2419 Mon Sep 17 00:00:00 2001
From: Richard Henderson <richard.henderson@linaro.org>
Date: Wed, 3 Mar 2021 20:45:20 -0500
Subject: [PATCH] tcg: Add temp_readonly

In most, but not all, places that we check for TEMP_FIXED,
we are really testing that we do not modify the temporary.

Backports e01fa97dea857a35be5bb8cce0d632a62e72c689
---
 qemu/tcg/tcg.c | 21 ++++++++++-----------
 qemu/tcg/tcg.h |  5 +++++
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/qemu/tcg/tcg.c b/qemu/tcg/tcg.c
index 33f90591..47af402d 100644
--- a/qemu/tcg/tcg.c
+++ b/qemu/tcg/tcg.c
@@ -2605,7 +2605,7 @@ static void temp_load(TCGContext *, TCGTemp *, TCGRegSet, TCGRegSet, TCGRegSet);
    mark it free; otherwise mark it dead.  */
 static void temp_free_or_dead(TCGContext *s, TCGTemp *ts, int free_or_dead)
 {
-    if (ts->kind == TEMP_FIXED) {
+    if (temp_readonly(ts)) {
         return;
     }
     if (ts->val_type == TEMP_VAL_REG) {
@@ -2629,7 +2629,7 @@ static inline void temp_dead(TCGContext *s, TCGTemp *ts)
 static void temp_sync(TCGContext *s, TCGTemp *ts, TCGRegSet allocated_regs,
                       TCGRegSet preferred_regs, int free_or_dead)
 {
-    if (ts->kind == TEMP_FIXED) {
+    if (temp_readonly(ts)) {
         return;
     }
     if (!ts->mem_coherent) {
@@ -2812,8 +2812,7 @@ static void temp_save(TCGContext *s, TCGTemp *ts, TCGRegSet allocated_regs)
 {
     /* The liveness analysis already ensures that globals are back
        in memory. Keep an tcg_debug_assert for safety. */
-    tcg_debug_assert(ts->val_type == TEMP_VAL_MEM
-                     || ts->kind == TEMP_FIXED);
+    tcg_debug_assert(ts->val_type == TEMP_VAL_MEM || temp_readonly(ts));
 }
 
 /* save globals to their canonical location and assume they can be
@@ -2871,7 +2870,7 @@ static void tcg_reg_alloc_do_movi(TCGContext *s, TCGTemp *ots,
                                   TCGRegSet preferred_regs)
 {
     /* ENV should not be modified.  */
-    tcg_debug_assert(ots->kind != TEMP_FIXED);
+    tcg_debug_assert(!temp_readonly(ots));
 
     /* The movi is not explicitly generated here.  */
     if (ots->val_type == TEMP_VAL_REG) {
@@ -2911,7 +2910,7 @@ static void tcg_reg_alloc_mov(TCGContext *s, const TCGOp *op)
     ts = arg_temp(op->args[1]);
 
     /* ENV should not be modified.  */
-    tcg_debug_assert(ots->kind != TEMP_FIXED);
+    tcg_debug_assert(!temp_readonly(ots));
 
     /* Note that otype != itype for no-op truncation.  */
     otype = ots->type;
@@ -2972,7 +2971,7 @@ static void tcg_reg_alloc_mov(TCGContext *s, const TCGOp *op)
                  * Store the source register into the destination slot
                  * and leave the destination temp as TEMP_VAL_MEM.
                  */
-                assert(ots->kind != TEMP_FIXED);
+                assert(!temp_readonly(ots));
                 if (!ts->mem_allocated) {
                     temp_allocate_frame(s, ots);
                 }
@@ -3009,7 +3008,7 @@ static void tcg_reg_alloc_dup(TCGContext *s, const TCGOp *op)
     its = arg_temp(op->args[1]);
 
     /* ENV should not be modified.  */
-    tcg_debug_assert(ots->kind != TEMP_FIXED);
+    tcg_debug_assert(!temp_readonly(ots));
 
     itype = its->type;
     vece = TCGOP_VECE(op);
@@ -3239,7 +3238,7 @@ static void tcg_reg_alloc_op(TCGContext *s, const TCGOp *op)
             ts = arg_temp(arg);
 
             /* ENV should not be modified.  */
-            tcg_debug_assert(ts->kind != TEMP_FIXED);
+            tcg_debug_assert(!temp_readonly(ts));
 
             if (arg_ct->oalias && !const_args[arg_ct->alias_index]) {
                 reg = new_args[arg_ct->alias_index];
@@ -3280,7 +3279,7 @@ static void tcg_reg_alloc_op(TCGContext *s, const TCGOp *op)
         ts = arg_temp(op->args[i]);
 
         /* ENV should not be modified.  */
-        tcg_debug_assert(ts->kind != TEMP_FIXED);
+        tcg_debug_assert(!temp_readonly(ts));
 
         if (NEED_SYNC_ARG(i)) {
             temp_sync(s, ts, o_allocated_regs, 0, IS_DEAD_ARG(i));
@@ -3412,7 +3411,7 @@ static void tcg_reg_alloc_call(TCGContext *s, TCGOp *op)
         ts = arg_temp(arg);
 
         /* ENV should not be modified.  */
-        tcg_debug_assert(ts->kind != TEMP_FIXED);
+        tcg_debug_assert(!temp_readonly(ts));
 
         reg = tcg_target_call_oarg_regs[i];
         tcg_debug_assert(s->reg_to_temp[reg] == NULL);
diff --git a/qemu/tcg/tcg.h b/qemu/tcg/tcg.h
index 05aee6d7..ca9a8ce5 100644
--- a/qemu/tcg/tcg.h
+++ b/qemu/tcg/tcg.h
@@ -875,6 +875,11 @@ struct TCGContext {
     TCGLabel *exitreq_label;  // gen_tb_start()
 };
 
+static inline bool temp_readonly(TCGTemp *ts)
+{
+    return ts->kind == TEMP_FIXED;
+}
+
 static inline size_t temp_idx(TCGContext *tcg_ctx, TCGTemp *ts)
 {
     ptrdiff_t n = ts - tcg_ctx->temps;