https://llvm.org/bugs/show_bug.cgi?id=28674
Bug ID: 28674
Summary: Failure to re-use immediate shared between compare and
subtract
Product: new-bugs
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: unassignedb...@nondot.org
Reporter: simon.ho...@arm.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Given:
uint32_t f(uint32_t x) { x++; return x < 4000569407 ? x : x - 4000569407; }
Compiling with:
clang --target=arm-linux-gnueabihf -O3 -S -o- p1modk.c
I get:
ldr r2, .LCPI2_0 // =294397890
ldr r3, .LCPI2_1 // =4000569407
add r1, r0, #1
cmp r1, r3
addhs r1, r0, r2
mov r0, r1
I expect:
ldr r1, .LCPI2_1 // =4000569407
add r0, r0, #1
cmp r0, r1
subhs r0, r0, r1
Or possibly (unless I made a mistake):
ldr r1, .LCPI2_1 // =(4000569407 - 1)
subs r1, r0, r1
addlo r1, r0, #1
mov r0, r1
Seems to affect at least x86, ARM, and AArch64.
--
You are receiving this mail because:
You are on the CC list for the bug.
_______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
