My apologies, I forgot to attach the files.
----- Original Message -----
From: Gabriel Marcano <gabemarcano@xxxxxxxxx>
To: "gcc-help@xxxxxxxxxxx" <gcc-help@xxxxxxxxxxx>
Sent: Wednesday, June 1, 2016 7:23 PM
Subject: arm-none-eabi-gcc 5.3 and LTO, mixing ARM and Thumb instructions
Could someone help me understand this behavior with LTO? I am working with an
ARM cross compiler, arm-none-eabi. I am trying to make the compiler compile two
separate files in different ARM modes/targets, one of them in ARM, one of them
in Thumb. When I compile the two source files without -flto, one with -mthumb
-thumb-interwork, and the other with the same flags just -marm appended as to
override -mthumb, the resulting binary, when dissasembled with objdump, has code
in both modes, and it is rather aparent. When I enable -flto, the resulting
program ends up in a single mode, all of it.
I am attaching a couple of files to this email:
arm.c : The file to be compiled as ARM
main.c : The main function, compiled as Thumb
Makefile : Add -flto to LDFLAGS and CFLAGS to enable lto, remvove it to
disable it.
lto.txt : The arm-none-eabi-objdump dissassembly of the resulting lto
binary.
no-lto.txt : the arm-none-eabi-objdump dissassembly of the resulting binary
without lto.
Is there something obvious about the behavior of LTO that I'm missing? Does it
just generate the final machine code at link time, scrapping the flags used to
compile object files?
Thanks,
Gabriel E. Marcano
int foo(int a, int b)
{
return a + b;
}
main: file format elf32-littlearm
Disassembly of section .init:
00008000 <_init>:
8000: b5f8 push {r3, r4, r5, r6, r7, lr}
8002: 46c0 nop ; (mov r8, r8)
8004: bcf8 pop {r3, r4, r5, r6, r7}
8006: bc08 pop {r3}
8008: 469e mov lr, r3
800a: 4770 bx lr
Disassembly of section .text:
0000800c <deregister_tm_clones>:
800c: 4b07 ldr r3, [pc, #28] ; (802c <deregister_tm_clones+0x20>)
800e: 4808 ldr r0, [pc, #32] ; (8030 <deregister_tm_clones+0x24>)
8010: 3303 adds r3, #3
8012: b510 push {r4, lr}
8014: 1a1b subs r3, r3, r0
8016: 2b06 cmp r3, #6
8018: d904 bls.n 8024 <deregister_tm_clones+0x18>
801a: 4b06 ldr r3, [pc, #24] ; (8034 <deregister_tm_clones+0x28>)
801c: 2b00 cmp r3, #0
801e: d001 beq.n 8024 <deregister_tm_clones+0x18>
8020: f000 f85c bl 80dc <frame_dummy+0x44>
8024: bc10 pop {r4}
8026: bc01 pop {r0}
8028: 4700 bx r0
802a: 46c0 nop ; (mov r8, r8)
802c: 00018140 .word 0x00018140
8030: 00018140 .word 0x00018140
8034: 00000000 .word 0x00000000
00008038 <register_tm_clones>:
8038: 4808 ldr r0, [pc, #32] ; (805c <register_tm_clones+0x24>)
803a: 4909 ldr r1, [pc, #36] ; (8060 <register_tm_clones+0x28>)
803c: 1a09 subs r1, r1, r0
803e: 1089 asrs r1, r1, #2
8040: 0fcb lsrs r3, r1, #31
8042: 1859 adds r1, r3, r1
8044: b510 push {r4, lr}
8046: 1049 asrs r1, r1, #1
8048: d004 beq.n 8054 <register_tm_clones+0x1c>
804a: 4b06 ldr r3, [pc, #24] ; (8064 <register_tm_clones+0x2c>)
804c: 2b00 cmp r3, #0
804e: d001 beq.n 8054 <register_tm_clones+0x1c>
8050: f000 f844 bl 80dc <frame_dummy+0x44>
8054: bc10 pop {r4}
8056: bc01 pop {r0}
8058: 4700 bx r0
805a: 46c0 nop ; (mov r8, r8)
805c: 00018140 .word 0x00018140
8060: 00018140 .word 0x00018140
8064: 00000000 .word 0x00000000
00008068 <__do_global_dtors_aux>:
8068: b510 push {r4, lr}
806a: 4c08 ldr r4, [pc, #32] ; (808c <__do_global_dtors_aux+0x24>)
806c: 7823 ldrb r3, [r4, #0]
806e: 2b00 cmp r3, #0
8070: d109 bne.n 8086 <__do_global_dtors_aux+0x1e>
8072: f7ff ffcb bl 800c <deregister_tm_clones>
8076: 4b06 ldr r3, [pc, #24] ; (8090 <__do_global_dtors_aux+0x28>)
8078: 2b00 cmp r3, #0
807a: d002 beq.n 8082 <__do_global_dtors_aux+0x1a>
807c: 4805 ldr r0, [pc, #20] ; (8094 <__do_global_dtors_aux+0x2c>)
807e: e000 b.n 8082 <__do_global_dtors_aux+0x1a>
8080: bf00 nop
8082: 2301 movs r3, #1
8084: 7023 strb r3, [r4, #0]
8086: bc10 pop {r4}
8088: bc01 pop {r0}
808a: 4700 bx r0
808c: 00018140 .word 0x00018140
8090: 00000000 .word 0x00000000
8094: 0000812c .word 0x0000812c
00008098 <frame_dummy>:
8098: 4b0b ldr r3, [pc, #44] ; (80c8 <frame_dummy+0x30>)
809a: b510 push {r4, lr}
809c: 2b00 cmp r3, #0
809e: d003 beq.n 80a8 <frame_dummy+0x10>
80a0: 490a ldr r1, [pc, #40] ; (80cc <frame_dummy+0x34>)
80a2: 480b ldr r0, [pc, #44] ; (80d0 <frame_dummy+0x38>)
80a4: e000 b.n 80a8 <frame_dummy+0x10>
80a6: bf00 nop
80a8: 480a ldr r0, [pc, #40] ; (80d4 <frame_dummy+0x3c>)
80aa: 6803 ldr r3, [r0, #0]
80ac: 2b00 cmp r3, #0
80ae: d104 bne.n 80ba <frame_dummy+0x22>
80b0: f7ff ffc2 bl 8038 <register_tm_clones>
80b4: bc10 pop {r4}
80b6: bc01 pop {r0}
80b8: 4700 bx r0
80ba: 4b07 ldr r3, [pc, #28] ; (80d8 <frame_dummy+0x40>)
80bc: 2b00 cmp r3, #0
80be: d0f7 beq.n 80b0 <frame_dummy+0x18>
80c0: f000 f80c bl 80dc <frame_dummy+0x44>
80c4: e7f4 b.n 80b0 <frame_dummy+0x18>
80c6: 46c0 nop ; (mov r8, r8)
80c8: 00000000 .word 0x00000000
80cc: 00018144 .word 0x00018144
80d0: 0000812c .word 0x0000812c
80d4: 00018138 .word 0x00018138
80d8: 00000000 .word 0x00000000
80dc: 4718 bx r3
80de: 46c0 nop ; (mov r8, r8)
000080e0 <main>:
80e0: b580 push {r7, lr}
80e2: af00 add r7, sp, #0
80e4: 4a05 ldr r2, [pc, #20] ; (80fc <main+0x1c>)
80e6: 4b06 ldr r3, [pc, #24] ; (8100 <main+0x20>)
80e8: 0011 movs r1, r2
80ea: 0018 movs r0, r3
80ec: f000 f80a bl 8104 <foo>
80f0: 0003 movs r3, r0
80f2: 0018 movs r0, r3
80f4: 46bd mov sp, r7
80f6: bc80 pop {r7}
80f8: bc02 pop {r1}
80fa: 4708 bx r1
80fc: 0000beef .word 0x0000beef
8100: 0000dead .word 0x0000dead
00008104 <foo>:
8104: b580 push {r7, lr}
8106: b082 sub sp, #8
8108: af00 add r7, sp, #0
810a: 6078 str r0, [r7, #4]
810c: 6039 str r1, [r7, #0]
810e: 687a ldr r2, [r7, #4]
8110: 683b ldr r3, [r7, #0]
8112: 18d3 adds r3, r2, r3
8114: 0018 movs r0, r3
8116: 46bd mov sp, r7
8118: b002 add sp, #8
811a: bc80 pop {r7}
811c: bc02 pop {r1}
811e: 4708 bx r1
Disassembly of section .fini:
00008120 <_fini>:
8120: b5f8 push {r3, r4, r5, r6, r7, lr}
8122: 46c0 nop ; (mov r8, r8)
8124: bcf8 pop {r3, r4, r5, r6, r7}
8126: bc08 pop {r3}
8128: 469e mov lr, r3
812a: 4770 bx lr
int foo(int a, int b);
int main()
{
return foo(0xDEAD, 0xBEEF);
}
Attachment:
Makefile
Description: Binary data
main: file format elf32-littlearm
Disassembly of section .init:
00008000 <_init>:
8000: b5f8 push {r3, r4, r5, r6, r7, lr}
8002: 46c0 nop ; (mov r8, r8)
8004: bcf8 pop {r3, r4, r5, r6, r7}
8006: bc08 pop {r3}
8008: 469e mov lr, r3
800a: 4770 bx lr
Disassembly of section .text:
00008010 <deregister_tm_clones>:
8010: 4b07 ldr r3, [pc, #28] ; (8030 <deregister_tm_clones+0x20>)
8012: 4808 ldr r0, [pc, #32] ; (8034 <deregister_tm_clones+0x24>)
8014: 3303 adds r3, #3
8016: b510 push {r4, lr}
8018: 1a1b subs r3, r3, r0
801a: 2b06 cmp r3, #6
801c: d904 bls.n 8028 <deregister_tm_clones+0x18>
801e: 4b06 ldr r3, [pc, #24] ; (8038 <deregister_tm_clones+0x28>)
8020: 2b00 cmp r3, #0
8022: d001 beq.n 8028 <deregister_tm_clones+0x18>
8024: f000 f85c bl 80e0 <frame_dummy+0x44>
8028: bc10 pop {r4}
802a: bc01 pop {r0}
802c: 4700 bx r0
802e: 46c0 nop ; (mov r8, r8)
8030: 00018160 .word 0x00018160
8034: 00018160 .word 0x00018160
8038: 00000000 .word 0x00000000
0000803c <register_tm_clones>:
803c: 4808 ldr r0, [pc, #32] ; (8060 <register_tm_clones+0x24>)
803e: 4909 ldr r1, [pc, #36] ; (8064 <register_tm_clones+0x28>)
8040: 1a09 subs r1, r1, r0
8042: 1089 asrs r1, r1, #2
8044: 0fcb lsrs r3, r1, #31
8046: 1859 adds r1, r3, r1
8048: b510 push {r4, lr}
804a: 1049 asrs r1, r1, #1
804c: d004 beq.n 8058 <register_tm_clones+0x1c>
804e: 4b06 ldr r3, [pc, #24] ; (8068 <register_tm_clones+0x2c>)
8050: 2b00 cmp r3, #0
8052: d001 beq.n 8058 <register_tm_clones+0x1c>
8054: f000 f844 bl 80e0 <frame_dummy+0x44>
8058: bc10 pop {r4}
805a: bc01 pop {r0}
805c: 4700 bx r0
805e: 46c0 nop ; (mov r8, r8)
8060: 00018160 .word 0x00018160
8064: 00018160 .word 0x00018160
8068: 00000000 .word 0x00000000
0000806c <__do_global_dtors_aux>:
806c: b510 push {r4, lr}
806e: 4c08 ldr r4, [pc, #32] ; (8090 <__do_global_dtors_aux+0x24>)
8070: 7823 ldrb r3, [r4, #0]
8072: 2b00 cmp r3, #0
8074: d109 bne.n 808a <__do_global_dtors_aux+0x1e>
8076: f7ff ffcb bl 8010 <deregister_tm_clones>
807a: 4b06 ldr r3, [pc, #24] ; (8094 <__do_global_dtors_aux+0x28>)
807c: 2b00 cmp r3, #0
807e: d002 beq.n 8086 <__do_global_dtors_aux+0x1a>
8080: 4805 ldr r0, [pc, #20] ; (8098 <__do_global_dtors_aux+0x2c>)
8082: e000 b.n 8086 <__do_global_dtors_aux+0x1a>
8084: bf00 nop
8086: 2301 movs r3, #1
8088: 7023 strb r3, [r4, #0]
808a: bc10 pop {r4}
808c: bc01 pop {r0}
808e: 4700 bx r0
8090: 00018160 .word 0x00018160
8094: 00000000 .word 0x00000000
8098: 0000814c .word 0x0000814c
0000809c <frame_dummy>:
809c: 4b0b ldr r3, [pc, #44] ; (80cc <frame_dummy+0x30>)
809e: b510 push {r4, lr}
80a0: 2b00 cmp r3, #0
80a2: d003 beq.n 80ac <frame_dummy+0x10>
80a4: 490a ldr r1, [pc, #40] ; (80d0 <frame_dummy+0x34>)
80a6: 480b ldr r0, [pc, #44] ; (80d4 <frame_dummy+0x38>)
80a8: e000 b.n 80ac <frame_dummy+0x10>
80aa: bf00 nop
80ac: 480a ldr r0, [pc, #40] ; (80d8 <frame_dummy+0x3c>)
80ae: 6803 ldr r3, [r0, #0]
80b0: 2b00 cmp r3, #0
80b2: d104 bne.n 80be <frame_dummy+0x22>
80b4: f7ff ffc2 bl 803c <register_tm_clones>
80b8: bc10 pop {r4}
80ba: bc01 pop {r0}
80bc: 4700 bx r0
80be: 4b07 ldr r3, [pc, #28] ; (80dc <frame_dummy+0x40>)
80c0: 2b00 cmp r3, #0
80c2: d0f7 beq.n 80b4 <frame_dummy+0x18>
80c4: f000 f80c bl 80e0 <frame_dummy+0x44>
80c8: e7f4 b.n 80b4 <frame_dummy+0x18>
80ca: 46c0 nop ; (mov r8, r8)
80cc: 00000000 .word 0x00000000
80d0: 00018164 .word 0x00018164
80d4: 0000814c .word 0x0000814c
80d8: 00018158 .word 0x00018158
80dc: 00000000 .word 0x00000000
80e0: 4718 bx r3
80e2: 46c0 nop ; (mov r8, r8)
000080e4 <main>:
80e4: b580 push {r7, lr}
80e6: af00 add r7, sp, #0
80e8: 4a05 ldr r2, [pc, #20] ; (8100 <main+0x1c>)
80ea: 4b06 ldr r3, [pc, #24] ; (8104 <main+0x20>)
80ec: 0011 movs r1, r2
80ee: 0018 movs r0, r3
80f0: f000 f822 bl 8138 <__foo_from_thumb>
80f4: 0003 movs r3, r0
80f6: 0018 movs r0, r3
80f8: 46bd mov sp, r7
80fa: bc80 pop {r7}
80fc: bc02 pop {r1}
80fe: 4708 bx r1
8100: 0000beef .word 0x0000beef
8104: 0000dead .word 0x0000dead
00008108 <foo>:
8108: e52db004 push {fp} ; (str fp, [sp, #-4]!)
810c: e28db000 add fp, sp, #0
8110: e24dd00c sub sp, sp, #12
8114: e50b0008 str r0, [fp, #-8]
8118: e50b100c str r1, [fp, #-12]
811c: e51b2008 ldr r2, [fp, #-8]
8120: e51b300c ldr r3, [fp, #-12]
8124: e0823003 add r3, r2, r3
8128: e1a00003 mov r0, r3
812c: e24bd000 sub sp, fp, #0
8130: e49db004 pop {fp} ; (ldr fp, [sp], #4)
8134: e12fff1e bx lr
00008138 <__foo_from_thumb>:
8138: 4778 bx pc
813a: 46c0 nop ; (mov r8, r8)
813c: eafffff1 b 8108 <foo>
Disassembly of section .fini:
00008140 <_fini>:
8140: b5f8 push {r3, r4, r5, r6, r7, lr}
8142: 46c0 nop ; (mov r8, r8)
8144: bcf8 pop {r3, r4, r5, r6, r7}
8146: bc08 pop {r3}
8148: 469e mov lr, r3
814a: 4770 bx lr
