console: bounds check whenever changing the cursor due to an escape code

[mirror_qemu.git] / tcg / README

diff --git a/tcg/README b/tcg/README
index a50ecc658827a2450b1aaee532851e3ce7bfdb52..cfdfd96d0953cda6f8619799f4a0935ea363f6ac 100644 (file)
--- a/tcg/README
+++ b/tcg/README
@@ -285,10 +285,10 @@ the four high order bytes are set to zero.
 Indicate that the value of t0 won't be used later. It is useful to
 force dead code elimination.
 
-* deposit_i32/i64 dest, t1, t2, pos, loc
+* deposit_i32/i64 dest, t1, t2, pos, len
 
 Deposit T2 as a bitfield into T1, placing the result in DEST.
-The bitfield is described by POS/LOC, which are immediate values:
+The bitfield is described by POS/LEN, which are immediate values:
 
   LEN - the length of the bitfield
   POS - the position of the first bit, counting from the LSB
@@ -504,7 +504,15 @@ register.
 - Don't hesitate to use helpers for complicated or seldom used target
   instructions. There is little performance advantage in using TCG to
   implement target instructions taking more than about twenty TCG
-  instructions.
+  instructions. Note that this rule of thumb is more applicable to
+  helpers doing complex logic or arithmetic, where the C compiler has
+  scope to do a good job of optimisation; it is less relevant where
+  the instruction is mostly doing loads and stores, and in those cases
+  inline TCG may still be faster for longer sequences.
+
+- The hard limit on the number of TCG instructions you can generate
+  per target instruction is set by MAX_OP_PER_INSTR in exec-all.h --
+  you cannot exceed this without risking a buffer overrun.
 
 - Use the 'discard' instruction if you know that TCG won't be able to
   prove that a given global is "dead" at a given program point. The