From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 26773 invoked by alias); 12 Jun 2009 12:54:24 -0000 Received: (qmail 26735 invoked by uid 48); 12 Jun 2009 12:54:08 -0000 Date: Fri, 12 Jun 2009 12:54:00 -0000 Message-ID: <20090612125408.26734.qmail@sourceware.org> X-Bugzilla-Reason: CC References: Subject: [Bug target/40416] unnecessary register spill In-Reply-To: Reply-To: gcc-bugzilla@gcc.gnu.org To: gcc-bugs@gcc.gnu.org From: "ramana at gcc dot gnu dot org" Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2009-06/txt/msg00769.txt.bz2 ------- Comment #2 from ramana at gcc dot gnu dot org 2009-06-12 12:54 ------- (In reply to comment #1) > Created an attachment (id=17983) --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17983&action=view) [edit] > test case > Your attachment didn't have #include - Please try and supply pre-processed input which is self contained . Adding a -I from a build directory can be rather painful . Thanks - > The spilling is occurred around the first loop: > > push {r4, r5, r6, r7, lr} > sub sp, sp, #12 > .loc 1 5 0 > str r2, [sp, #4] // A > .loc 1 6 0 > add r6, r1, r2 > mov r4, r0 > .loc 1 8 0 > b .L2 > .L5: > .loc 1 10 0 > mov r7, #0 > ldrsh r5, [r4, r7] > .loc 1 12 0 > cmp r2, r5 > bge .L3 > .loc 1 14 0 > ldrb r7, [r1] > strb r7, [r1, r2] > .loc 1 15 0 > strh r2, [r4] > .loc 1 16 0 > lsl r1, r2, #1 > sub r2, r5, r2 > strh r2, [r1, r4] > .L6: > .loc 1 5 0 > ldr r5, [sp, #4] // B > lsl r4, r5, #1 > add r0, r0, r4 > b .L4 > .L3: > .loc 1 19 0 > lsl r7, r5, #1 > mov ip, r7 > add r4, r4, ip > .loc 1 20 0 > add r1, r1, r5 > .loc 1 21 0 > sub r2, r2, r5 > .L2: > .loc 1 8 0 > cmp r2, #0 > bgt .L5 > b .L6 > .L4: > .loc 1 30 0 > mov r1, #0 > > > The spilling is occurred at instruction A and reload at instruction B. > > The spilled value is x. The source code computes next_runs and next_alpha > before while loop and preserve them through the loop body. But the generated > code preserve next_alpha, original runs and original x through the loop body > and compute next_runs after the loop. This caused an extra usage of register > and results in a register spilling. > Could you say what you'd like the code to be because I don't see an option but to spill one of the values here. ? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40416