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From: "spop at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/62173] New: [AArch64] Performance regression due to r213488 Date: Mon, 18 Aug 2014 16:12:00 -0000 [thread overview] Message-ID: <bug-62173-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62173 Bug ID: 62173 Summary: [AArch64] Performance regression due to r213488 Product: gcc Version: 5.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: spop at gcc dot gnu.org void bar(int i) { char A[10]; int d = 0; while (i > 0) A[d++] = i--; while (d > 0) foo(A[d--]); } Compile this function at -O3 with the last good revision r213487 and with the first bad revision r213488 "[AArch64] Improve TARGET_LEGITIMIZE_ADDRESS_P hook", and diffing: --- good.s 2014-08-18 10:56:42.542867000 -0500 +++ bad.s 2014-08-18 10:56:42.504090000 -0500 @@ -8,34 +8,33 @@ stp x29, x30, [sp, -48]! cmp w0, wzr add x29, sp, 0 - stp x19, x20, [sp, 16] + str x19, [sp, 16] ble .L1 strb w0, [x29, 32] subs w19, w0, #1 - add x20, x29, 32 beq .L4 strb w19, [x29, 33] subs w1, w0, #2 beq .L4 - strb w1, [x20, 2] + strb w1, [x29, 34] subs w1, w0, #3 beq .L4 - strb w1, [x20, 3] + strb w1, [x29, 35] subs w1, w0, #4 beq .L4 - strb w1, [x20, 4] + strb w1, [x29, 36] subs w1, w0, #5 beq .L4 - strb w1, [x20, 5] + strb w1, [x29, 37] subs w1, w0, #6 beq .L4 - strb w1, [x20, 6] + strb w1, [x29, 38] subs w1, w0, #7 beq .L4 - strb w1, [x20, 7] + strb w1, [x29, 39] subs w1, w0, #8 beq .L4 - strb w1, [x20, 8] + strb w1, [x29, 40] subs w1, w0, #9 beq .L4 strb w1, [x29, 41] @@ -43,14 +42,16 @@ .L35: sub w19, w19, #1 .L4: - ldrb w0, [x20, w0, sxtw] + add x1, x29, 48 + add x0, x1, x0, sxtw + ldrb w0, [x0, -16] bl foo mov w0, w19 cbnz w19, .L35 .L1: - ldp x19, x20, [sp, 16] + ldr x19, [sp, 16] ldp x29, x30, [sp], 48 ret .size bar, .-bar The problem is that gcc now generates an addressing mode that requires two more add instructions in the second loop: - ldrb w0, [x20, w0, sxtw] + add x1, x29, 48 + add x0, x1, x0, sxtw + ldrb w0, [x0, -16]
next reply other threads:[~2014-08-18 16:12 UTC|newest] Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-08-18 16:12 spop at gcc dot gnu.org [this message] 2014-08-18 16:39 ` [Bug target/62173] " pinskia at gcc dot gnu.org 2014-08-18 19:13 ` spop at gcc dot gnu.org 2014-08-19 1:37 ` amker at gcc dot gnu.org 2014-10-28 11:28 ` [Bug target/62173] [5.0 regression] " jiwang at gcc dot gnu.org 2014-11-14 9:37 ` jiwang at gcc dot gnu.org 2014-11-17 2:14 ` amker.cheng at gmail dot com 2014-11-24 12:15 ` jiwang at gcc dot gnu.org 2014-11-24 12:38 ` jiwang at gcc dot gnu.org 2014-11-24 13:06 ` rguenth at gcc dot gnu.org 2014-11-24 23:01 ` jiwang at gcc dot gnu.org 2014-11-26 10:54 ` [Bug target/62173] [5.0 regression] [AArch64] Can't ivopt array base address while ARM can jiwang at gcc dot gnu.org 2014-11-27 9:35 ` jiwang at gcc dot gnu.org 2014-11-27 12:00 ` [Bug tree-optimization/62173] [5.0 regression] 64bit Arch can't ivopt while 32bit Arch can rguenther at suse dot de 2014-11-27 12:16 ` rguenther at suse dot de 2014-11-27 13:34 ` jiwang at gcc dot gnu.org 2015-01-23 17:33 ` jiwang at gcc dot gnu.org 2015-01-26 10:30 ` rguenth at gcc dot gnu.org 2015-01-26 11:10 ` rguenth at gcc dot gnu.org 2015-01-26 13:48 ` ramana at gcc dot gnu.org 2015-01-26 14:19 ` amker at gcc dot gnu.org 2015-01-26 14:51 ` rguenther at suse dot de 2015-01-26 14:53 ` rguenther at suse dot de 2015-01-26 15:03 ` amker at gcc dot gnu.org 2015-01-26 15:38 ` jiwang at gcc dot gnu.org 2015-01-27 3:21 ` amker at gcc dot gnu.org 2015-01-27 7:56 ` amker at gcc dot gnu.org 2015-01-27 9:11 ` rguenther at suse dot de 2015-01-28 18:26 ` LpSolit at netscape dot net 2015-01-29 6:48 ` amker at gcc dot gnu.org 2015-01-30 6:42 ` amker at gcc dot gnu.org 2015-01-30 12:32 ` rguenth at gcc dot gnu.org 2015-02-05 7:27 ` amker at gcc dot gnu.org 2015-03-11 17:30 ` [Bug tree-optimization/62173] [5 Regression] " jiwang at gcc dot gnu.org 2015-03-11 17:46 ` jiwang at gcc dot gnu.org 2015-03-11 17:52 ` [Bug tree-optimization/62173] [5/6 " jakub at gcc dot gnu.org 2015-03-13 8:34 ` amker at gcc dot gnu.org 2015-06-02 3:34 ` amker at gcc dot gnu.org 2015-06-03 3:56 ` amker at gcc dot gnu.org 2015-07-22 11:44 ` jiwang at gcc dot gnu.org
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