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[Bug rtl-optimization/50088] movzbl is generated instead of movl
- From: "enkovich.gnu at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Mon, 15 Aug 2011 13:24:05 +0000
- Subject: [Bug rtl-optimization/50088] movzbl is generated instead of movl
- Auto-submitted: auto-generated
- References: <bug-50088-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50088
--- Comment #2 from Ilya Enkovich <enkovich.gnu at gmail dot com> 2011-08-15 13:24:05 UTC ---
Actually we do not need any zero extensions here. Zero extended load appears
only after IRA if we have to spill/fill register.
Here is c code from reproducer:
n1 = (n1 + 1) & 15;
s += arr[i] << n1;
RTL before IRA:
(insn 67 66 68 4 (parallel [
(set (reg/v:SI 97 [ n1 ])
(plus:SI (reg/v:SI 97 [ n1 ])
(const_int 1 [0x1])))
(clobber (reg:CC 17 flags))
]) test_movzbl.c:18 249 {*addsi_1}
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil)))
(insn 68 67 70 4 (parallel [
(set (reg/v:SI 97 [ n1 ])
(and:SI (reg/v:SI 97 [ n1 ])
(const_int 15 [0xf])))
(clobber (reg:CC 17 flags))
]) test_movzbl.c:18 385 {*andsi_1}
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil)))
(insn 70 68 71 4 (set (reg:SI 262)
(mem:SI (reg:SI 224 [ ivtmp.52 ]) [2 MEM[base: D.2889_232, offset:
0B]+0 S4 A32])) test_movzbl.c:20 64 {*movsi_internal}
(nil))
(insn 71 70 72 4 (parallel [
(set (reg:SI 262)
(ashift:SI (reg:SI 262)
(subreg:QI (reg/v:SI 97 [ n1 ]) 0)))
(clobber (reg:CC 17 flags))
]) test_movzbl.c:20 502 {*ashlsi3_1}
(expr_list:REG_UNUSED (reg:CC 17 flags)
(expr_list:REG_EQUAL (ashift:SI (mem:SI (reg:SI 224 [ ivtmp.52 ]) [2
MEM[base: D.2889_232, offset: 0B]+0 S4 A32])
(subreg:QI (reg/v:SI 97 [ n1 ]) 0))
(nil))))
IRA then introduces fill for shift instruction and use byte load for it:
(insn 155 70 71 4 (set (reg:QI 2 cx)
(mem/c:QI (reg/f:SI 7 sp) [4 %sfp+-28 S1 A32])) test_movzbl.c:20 66
{*movqi_internal}
(nil))
(insn 71 155 72 4 (parallel [
(set (reg:SI 5 di [262])
(ashift:SI (reg:SI 5 di [262])
(reg:QI 2 cx)))
(clobber (reg:CC 17 flags))
]) test_movzbl.c:20 502 {*ashlsi3_1}
(expr_list:REG_EQUAL (ashift:SI (mem:SI (reg:SI 0 ax [orig:224 ivtmp.52 ]
[224]) [2 MEM[base: D.2889_232, offset: 0B]+0 S4 A32])
(subreg:QI (mem/c:SI (reg/f:SI 7 sp) [4 %sfp+-28 S4 A32]) 0))
(nil)))
Load for shift then is emitted as movzbl.