* avr-gcc: direct register access suppresses optimization
@ 2023-02-14 9:32 Wilhelm Meier
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From: Wilhelm Meier @ 2023-02-14 9:32 UTC (permalink / raw)
To: gcc-help
The follwing example contains functional identicaal code:
<1> uses direct register access
<2> uses structure mapping
But <1> suppresses the hoist/sink of the loads/stores to variable g out
of the loop. In case <2> this optimization is done (and is correct).
What does avr-gcc hinder to do this optimization in case <1>?
#include <avr/io.h>
#include <stdint.h>
static uint16_t g;
int main() {
for(uint8_t i = 0; i < 20; i++) {
++g;
// VPORTA_DIR; // <1> suppresses optimization
VPORTA.DIR; // <2>
}
}
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2023-02-14 9:32 avr-gcc: direct register access suppresses optimization Wilhelm Meier
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