Compile the attached source code with options -march=armv7-a -mthumb -Os, gcc
generates following instructions for "if (start == -1 || end == -1)":
...
cmp r4, #-1
ite ne
movne r3, #0
moveq r3, #1
cmp r0, #-1
it eq
orreq r3, r3, #1
cbnz r3, .L4
...
A simplified code sequence is:
...
cmp r4, #-1
bne .L4
cmp r0, #-1
bne .L4
...
The if statement is trivially translated into the following gimple statements:
D.2530 = start == -1;
D.2531 = end == -1;
D.2532 = D.2530 || D.2531;
if (D.2532 != 0) goto <D.2533>; else goto <D.2534>;
And then expanded into rtl insns without further optimizations.
--
Summary: A lot of instructions for condition (start == -1 || end
== -1)
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: carrot at google dot com
GCC build triplet: i686-linux
GCC host triplet: i686-linux
GCC target triplet: arm-eabi
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43920
