From 3031244b01492528fd7b5e46b23eeb2124dc780a Mon Sep 17 00:00:00 2001 From: Aurelien Jarno Date: Tue, 3 Sep 2013 08:27:38 +0200 Subject: tcg/optimize: fix known-zero bits optimization Known-zero bits optimization is a great idea that helps to generate more optimized code. However the current implementation only works in very few cases as the computed mask is not saved. Fix this to make it really working. Reviewed-by: Paolo Bonzini Signed-off-by: Aurelien Jarno Signed-off-by: Richard Henderson --- tcg/optimize.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'tcg') diff --git a/tcg/optimize.c b/tcg/optimize.c index c5cdde2160..7838be2c50 100644 --- a/tcg/optimize.c +++ b/tcg/optimize.c @@ -691,7 +691,8 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr, break; } - /* Simplify using known-zero bits */ + /* Simplify using known-zero bits. Currently only ops with a single + output argument is supported. */ mask = -1; affected = -1; switch (op) { @@ -1149,6 +1150,11 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr, } else { for (i = 0; i < def->nb_oargs; i++) { reset_temp(args[i]); + /* Save the corresponding known-zero bits mask for the + first output argument (only one supported so far). */ + if (i == 0) { + temps[args[i]].mask = mask; + } } } for (i = 0; i < def->nb_args; i++) { -- cgit v1.2.1