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[Qemu-devel] [PATCH v5 01/11] trace: [tcg] Add documentation

From: Lluís Vilanova
Subject: [Qemu-devel] [PATCH v5 01/11] trace: [tcg] Add documentation
Date: Fri, 30 May 2014 14:11:26 +0200
User-agent: StGit/0.17.1-dirty

Signed-off-by: Lluís Vilanova <address@hidden>
 docs/tracing.txt |   40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/docs/tracing.txt b/docs/tracing.txt
index c6ab1c1..2e035a5 100644
--- a/docs/tracing.txt
+++ b/docs/tracing.txt
@@ -307,3 +307,43 @@ guard such computations and avoid its compilation when the 
event is disabled:
 You can check both if the event has been disabled and is dynamically enabled at
 the same time using the 'trace_event_get_state' routine (see header
 "trace/control.h" for more information).
+=== "tcg" ===
+Guest code generated by TCG can be traced by defining an event with the "tcg"
+event property. Internally, this property generates two events:
+"<eventname>_trans" to trace the event at translation time, and
+"<eventname>_exec" to trace the event at execution time.
+Instead of using these two events, you should instead use the function
+"trace_<eventname>_tcg" during translation (TCG code generation). This function
+will automatically call "trace_<eventname>_trans", and will generate the
+necessary TCG code to call "trace_<eventname>_exec" during guest code 
+Events with the "tcg" property can be declared in the "trace-events" file with 
+mix of native and TCG types, and "trace_<eventname>_tcg" will gracefully 
+them to the "<eventname>_trans" and "<eventname>_exec" events. Since TCG values
+are not known at translation time, these are ignored by the "<eventname>_trans"
+event. Because of this, the entry in the "trace-events" file needs two printing
+formats (separated by a comma):
+    tcg foo(uint8_t a1, TCGv_i32 a2) "a1=%d", "a1=%d a2=%d"
+For example:
+    #include "trace-tcg.h"
+    void some_disassembly_func (...)
+    {
+        uint8_t a1 = ...;
+        TCGv_i32 a2 = ...;
+        trace_foo_tcg(a1, a2);
+    }
+This will immediately call:
+    void trace_foo_trans(uint8_t a1);
+and will generate the TCG code to call:
+    void trace_foo(uint8_t a1, uint32_t a2);

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