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Revision 09aac126


Added by Richard Henderson over 14 years ago

tcg/x86_64: Avoid unnecessary REX.B prefixes.

The existing P_REXB internal opcode flag unconditionally emits
the REX prefix. Technically it's not needed if the register in
question is %al, %bl, %cl, %dl.

Eliding the prefix requires splitting the P_REXB flag into two,
in order to indicate whether the byte register in question is
in the REG or the R/M field. Within TCG, the byte register is
in the REG field only for stores.

Signed-off-by: Richard Henderson <>
Signed-off-by: Aurelien Jarno <>


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