tcg: Diagnose referenced labels that have not been emitted

Currently, a jump to a label that is not defined anywhere will
be emitted not be relocated.  This results in a jump to a random
jump target.  With tcg debugging, print a diagnostic to the -d op
file and abort.

This could help debug or detect errors like
c2d9644e6d ("target/arm: Fix crash on conditional instruction in an IT block")

Reported-by: Roman Kapl <code@rkapl.cz>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 9 insertions, 3 deletions

diff --git a/tcg/tcg.h b/tcg/tcg.h
index 045c24a..32b7cf3 100644
--- a/tcg/tcg.h
+++ b/tcg/tcg.h
@@ -244,16 +244,21 @@ typedef struct TCGRelocation {
     intptr_t addend;
 } TCGRelocation; 
 
-typedef struct TCGLabel {
+typedef struct TCGLabel TCGLabel;
+struct TCGLabel {
+    unsigned present : 1;
     unsigned has_value : 1;
-    unsigned id : 15;
+    unsigned id : 14;
     unsigned refs : 16;
     union {
         uintptr_t value;
         tcg_insn_unit *value_ptr;
         TCGRelocation *first_reloc;
     } u;
-} TCGLabel;
+#ifdef CONFIG_DEBUG_TCG
+    QSIMPLEQ_ENTRY(TCGLabel) next;
+#endif
+};
 
 typedef struct TCGPool {
     struct TCGPool *next;
@@ -685,6 +690,7 @@ struct TCGContext {
 #endif
 
 #ifdef CONFIG_DEBUG_TCG
+    QSIMPLEQ_HEAD(, TCGLabel) labels;
     int temps_in_use;
     int goto_tb_issue_mask;
 #endif