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From: "olegendo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/52394] SH Target: SH2A defunct bitops Date: Sun, 20 Sep 2015 03:37:00 -0000 [thread overview] Message-ID: <bug-52394-4-TqHWoyh8ma@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-52394-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52394 --- Comment #2 from Oleg Endo <olegendo at gcc dot gnu.org> --- The SH2A bitops seem to produce some of the insns, but it seems the generated code is either really bad (defeating the original purpose) or broken. For example: volatile struct { union { unsigned char BYTE; struct { unsigned char BIT7:1; unsigned char BIT6:1; unsigned char BIT5:1; unsigned char BIT4:1; unsigned char BIT3:1; unsigned char BIT2:1; unsigned char BIT1:1; unsigned char BIT0:1; } BIT; } ICR0; } USRSTR; int main (unsigned char a, unsigned char b, unsigned char c) { USRSTR.ICR0.BIT.BIT5 |= b & 1; return 0; } compiled with -m2a -mb -mbitops -O2: mov.l .L2,r2 // addr of USRSTR mov #1,r1 and r1,r5 // b & 1 mov #0,r0 bor.b #5,@(0,r2) // T |= (bit in mem) movt r7 // r7 = T mov.b @r2,r3 // load byte cmp/pl r7 // T = r7 mov #5,r7 movt r1 // r1 = T bclr #5,r3 // clear bit 5 of loaded byte shld r7,r1 // T << 5 or r3,r1 // OR bit mov.b r1,@r2 // write back rts/n It seems that this will produce funny results at the first bor.b insn because at function entry the T bit is undefined. The code should actually be something like this: mov.l .L2,r2 bld #0,r5 mov #0,r0 bor.b #5,@(0,r2) bst.b #5,@(0,r2)
next prev parent reply other threads:[~2015-09-20 3:37 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-02-27 2:51 [Bug target/52394] New: " olegendo at gcc dot gnu.org 2012-02-28 0:49 ` [Bug target/52394] " kkojima at gcc dot gnu.org 2015-09-20 3:37 ` olegendo at gcc dot gnu.org [this message] 2015-09-20 10:01 ` olegendo at gcc dot gnu.org
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