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From: William Tambe <tambewilliam@gmail.com>
Date: Wed, 21 Sep 2022 16:57:39 -0500
Message-ID: <CAF8i9mMcSaKEHWyCAB8r1PJFD4r9QiPB5uPoo9tvRmGL1geTEQ@mail.gmail.com>
Subject: help removing unnecessary zero-extension
To: gcc-help <gcc-help@gcc.gnu.org>
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Given following program:

    unsigned char var;
    int main() {
        return var;
    }

And compiled using:
pu32-elf-gcc -O3 -c -save-temps test.c

Unnecessary zero-extension gets generated after a memory byte load
which already zero-extend.

LOAD_EXTEND_OP has been defined as follow:
#define LOAD_EXTEND_OP(M) ZERO_EXTEND

Find complete port at:
https://github.com/fontamsoc/gcc/commit/45840063
And machine description at:
https://github.com/fontamsoc/gcc/blob/45840063/gcc/config/pu32/pu32.md

Any idea what else can be tried to prevent the unnecessary zero-extension ?