https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94986
Bug ID: 94986
Summary: missing diagnostic on ARM thumb2 compilation with -pg
when using r7 in inline asm
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: arnd at linaro dot org
Target Milestone: ---
I reported a bug against clang for a Linux kernel failure, but
it was suggested that the clang behavior is probably correct in this corner
case while gcc gets it wrong, see https://bugs.llvm.org/show_bug.cgi?id=45826
echo 'void f(void) { asm("mov r7, #0" ::: "r7"); }' | arm-linux-gnueabi-gcc
-march=armv7-a -O2 -mthumb -pg -S -xc -
silently accepts an inline asm statement that clobbers the frame pointer, but
gcc rejects the same code if any of '-O0', '-fomit-frame-pointer' or
'fno-omit-frame-pointer' are used:
<stdin>: In function 'f':
<stdin>:1:44: error: r7 cannot be used in 'asm' here
If using r7 in this case is indeed invalid, we need to ensure the kernel does
not do this, and having gcc reject it would be helpful.
