Part Number: RM57L843
I'm working with a program that needs to compute IP checksums, and it seems like there's a bug in the tiarmclang compiler. When I compile bug-report.c (using ARM-CGT-CLANG 4.0.3.LTS) under -Os, it drops lines 102 and 103:
fakehdr.zero = 0;
fakehdr.protocol = protocol;That is, the values are never stored to offsets 8 and 9 in memory. Then the output of the checksum computation is incorrect.
Compiling under -O0 produces the correct output (values are stored to offsets 8 and 9).
The bug seems to have been introduced sometime between 3.2.3.LTS and 4.0.0.LTS. The bug continues to exist up through 5.0.0.STS.
3.2.3.LTS:
84: 68d0 ldr r0, [r2, #12]
86: 2400 movs r4, #0
88: 6912 ldr r2, [r2, #16]
8a: f88d 1009 strb.w r1, [sp, #9]
8e: 4661 mov r1, r12
90: f88d 4008 strb.w r4, [sp, #8]
94: 9000 str r0, [sp]
96: fa9c f09c rev16.w r0, r12
9a: 9201 str r2, [sp, #4]
9c: f8ad 000a strh.w r0, [sp, #10]
a0: 4618 mov r0, r3
a2: f7ff fffe bl 0xa2 <checksum+0xa2> @ imm = #-4
4.0.0.LTS:
74: 68d0 ldr r0, [r2, #0xc]
76: ba4c rev16 r4, r1
78: 6912 ldr r2, [r2, #0x10]
7a: f8ad 400a strh.w r4, [sp, #0xa]
7e: e9cd 0200 strd r0, r2, [sp]
82: 4618 mov r0, r3
84: f7ff fffe bl 0x84 <checksum+0x84> @ imm = #-0x4
5.0.0.STS:
72: 68d0 ldr r0, [r2, #0xc]
74: ba4c rev16 r4, r1
76: 6912 ldr r2, [r2, #0x10]
78: f8ad 400a strh.w r4, [sp, #0xa]
7c: e9cd 0200 strd r0, r2, [sp]
80: 4618 mov r0, r3
82: f7ff fffe bl 0x82 <checksum+0x82> @ imm = #-0x4
