Thank you so much, this patch solves the compilation errors that I was seeing in the Intel compiler, and with gcc -O0 BTW, my charter is to compile the kernel with the Intel compiler, and my testing stops short of verifying that the kernel build actually works. Best regards, Melanie Blower -----Original Message----- From: H. Peter Anvin [mailto:hpa@xxxxxxxxx] Sent: Wednesday, November 21, 2012 4:35 PM To: Blower, Melanie Cc: tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; avi@xxxxxxxxxx; x86@xxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx Subject: Re: PROBLEM: compilation issue, inline assembly arch/x86/kvm/emulate.c fails at -O0 On 11/14/2012 11:45 AM, Blower, Melanie wrote: > [1.] gcc -O0 assembly arch/x86/kvm/emulate.c gets compilation failure > -- incorrect register restrictions [2.] Full description of the problem/report: > I'm trying to compile this file at -O0, but gcc chokes in register allocation at the inline assembly. > > In the ordinary Linux build, this file compiles with gcc at -O2, without compilation errors. > > At -O0, gcc chokes with this message: > gcc -w -c ./emulateE.c // (using preprocessed file) > ./emulateE.c: In function `em_mul_ex': > ./emulateE.c:1918:5: error: can't find a register in class `AREG' while reloading `asm' > ./emulateE.c:1918:5: error: `asm' operand has impossible constraints > > Explanation: > The file contains an inline asm of a kind: > > __asm__ __volatile__ ( " ..... " : > > "=m" ((ctxt)->eflags), "=&r" (_tmp), "+a" (*rax), "+d" (*rdx), "+qm"(ex) : > "i" (11), "m" ((ctxt)->src . val), "a" (*rax), "d" (*rdx)); > > Note that "+a" in inputs already means that eax is the return value. An then "a" is used as an output constraint too. > Hi Melanie, Can you test the attached patch? -hpa ��.n��������+%������w��{.n�����o�^n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�
