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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/86011] Inefficient code generated for ldivmod with constant value Date: Tue, 21 Dec 2021 11:39:23 +0000 [thread overview] Message-ID: <bug-86011-4-baR7LqSLbS@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-86011-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86011 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Target Milestone|--- |11.0 Resolution|--- |FIXED --- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Fixed in GCC 11: lsrs r1, r2, #30 push {r4, lr} orr r1, r1, r3, lsl #2 bic lr, r1, #-1073741824 bic r1, r2, #-1073741824 add r1, r1, lr asrs r4, r3, #31 add r3, r1, r3, lsr #28 and r1, r4, #137 add r3, r3, r1 movw r1, #57025 movt r1, 13617 bic r4, r4, #75 umull lr, r1, r1, r3 mov lr, #77 lsrs r1, r1, #4 mls r3, lr, r1, r3 movw r1, #14469 movt r1, 16171 add r3, r3, r4 str r3, [r0, #4] subs r2, r2, r3 umull r2, r1, r2, r1 str r2, [r0] pop {r4, pc} For: #define N 7723 struct foo { long a, b; }; struct foo test(long long x) { return (struct foo){x / N, x % N}; } GCC 11+ Produces: push {r4, lr} mov r4, r0 mov r1, r3 mov r0, r2 movs r3, #0 movw r2, #7723 bl __aeabi_ldivmod strd r0, r2, [r4] mov r0, r4 pop {r4, pc} Which is exactly what you want too.
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