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tcg: Check for overflow via highwater mark

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We currently pre-compute an worst case code size for any TB, which
works out to be 122kB.  Since the average TB size is near 1kB, this
wastes quite a lot of storage.

Instead, check for overflow in between generating code for each opcode.
The overhead of the check isn't measurable and wastage is minimized.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson
2015-10-07 20:36:53 +11:00
parent f293709c6a
commit b125f9dc7b
4 changed files with 40 additions and 16 deletions
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include/exec/exec-all.h
-6
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@@ -62,12 +62,6 @@ typedef struct TranslationBlock TranslationBlock;
#define OPC_BUF_SIZE 640
#define OPC_MAX_SIZE (OPC_BUF_SIZE - MAX_OP_PER_INSTR)
/* Maximum size a TCG op can expand to. This is complicated because a
single op may require several host instructions and register reloads.
For now take a wild guess at 192 bytes, which should allow at least
a couple of fixup instructions per argument. */
#define TCG_MAX_OP_SIZE 192
#define OPPARAM_BUF_SIZE (OPC_BUF_SIZE * MAX_OPC_PARAM)
#include "qemu/log.h"