https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99271
Bug ID: 99271 Summary: [10/11 regression] Wrong code for Arm-v8-m.main CMSE calling __gnu_cmse_nonsecure_call Product: gcc Version: 10.0 Status: UNCONFIRMED Keywords: wrong-code Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: rearnsha at gcc dot gnu.org Target Milestone: --- Target: arm The code fragment: typedef void (*f)(int) __attribute__((cmse_nonsecure_call)); void bar(f func, int a) { func(a); } When compiled with -O2 -mcmse -march=armv8-m.main -mthumb Incorrectly optimizes the code sequence so that the register used for the function pointer is not correctly initialized. The problem was introduced in r10-6017, so affects gcc-10 and gcc-11. Current code: mov r3, r0 mov r0, r1 push {r4, lr} lsrs r3, r3, #1 lsls r3, r3, #1 mov r1, r3 mov r2, r3 bl __gnu_cmse_nonsecure_call // r4 not initialized above. pop {r4, pc} Correct code push {r4, lr} mov r4, r0 mov r0, r1 lsrs r4, r4, #1 lsls r4, r4, #1 mov r1, r4 mov r2, r4 mov r3, r4 bl __gnu_cmse_nonsecure_call // r4 = function with LSB cleared. pop {r4, pc}