fix i8k inline asm to workaround miscompilation with newer gcc
This commit is contained in:
Kyle McMartin
parent
51157289c8
commit
cc7fb594a9
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@ -0,0 +1,84 @@
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commit 22d3243de86bc92d874abb7c5b185d5c47aba323
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Author: Jim Bos <jim876@xs4all.nl>
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Date: Mon Nov 15 21:22:37 2010 +0100
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Fix gcc 4.5.1 miscompiling drivers/char/i8k.c (again)
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The fix in commit 6b4e81db2552 ("i8k: Tell gcc that *regs gets
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clobbered") to work around the gcc miscompiling i8k.c to add "+m
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(*regs)" caused register pressure problems and a build failure.
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Changing the 'asm' statement to 'asm volatile' instead should prevent
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that and works around the gcc bug as well, so we can remove the "+m".
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[ Background on the gcc bug: a memory clobber fails to mark the function
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the asm resides in as non-pure (aka "__attribute__((const))"), so if
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the function does nothing else that triggers the non-pure logic, gcc
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will think that that function has no side effects at all. As a result,
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callers will be mis-compiled.
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Adding the "+m" made gcc see that it's not a pure function, and so
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does "asm volatile". The problem was never really the need to mark
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"*regs" as changed, since the memory clobber did that part - the
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problem was just a bug in the gcc "pure" function analysis - Linus ]
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Signed-off-by: Jim Bos <jim876@xs4all.nl>
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Acked-by: Jakub Jelinek <jakub@redhat.com>
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Cc: Andi Kleen <andi@firstfloor.org>
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Cc: Andreas Schwab <schwab@linux-m68k.org>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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commit 6b4e81db2552bad04100e7d5ddeed7e848f53b48
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Author: Jim Bos <jim876@xs4all.nl>
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Date: Sat Nov 13 12:13:53 2010 +0100
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i8k: Tell gcc that *regs gets clobbered
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More recent GCC caused the i8k driver to stop working, on Slackware
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compiler was upgraded from gcc-4.4.4 to gcc-4.5.1 after which it didn't
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work anymore, meaning the driver didn't load or gave total nonsensical
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output.
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As it turned out the asm(..) statement forgot to mention it modifies the
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*regs variable.
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Credits to Andi Kleen and Andreas Schwab for providing the fix.
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Signed-off-by: Jim Bos <jim876@xs4all.nl>
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Cc: Andi Kleen <andi@firstfloor.org>
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Cc: Andreas Schwab <schwab@linux-m68k.org>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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diff --git a/drivers/char/i8k.c b/drivers/char/i8k.c
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index 3bc0eef..d72433f 100644
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--- a/drivers/char/i8k.c
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+++ b/drivers/char/i8k.c
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@@ -120,7 +120,7 @@ static int i8k_smm(struct smm_regs *regs)
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int eax = regs->eax;
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#if defined(CONFIG_X86_64)
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- asm("pushq %%rax\n\t"
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+ asm volatile("pushq %%rax\n\t"
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"movl 0(%%rax),%%edx\n\t"
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"pushq %%rdx\n\t"
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"movl 4(%%rax),%%ebx\n\t"
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@@ -146,7 +146,7 @@ static int i8k_smm(struct smm_regs *regs)
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: "a"(regs)
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: "%ebx", "%ecx", "%edx", "%esi", "%edi", "memory");
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#else
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- asm("pushl %%eax\n\t"
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+ asm volatile("pushl %%eax\n\t"
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"movl 0(%%eax),%%edx\n\t"
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"push %%edx\n\t"
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"movl 4(%%eax),%%ebx\n\t"
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@@ -167,7 +167,8 @@ static int i8k_smm(struct smm_regs *regs)
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"movl %%edx,0(%%eax)\n\t"
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"lahf\n\t"
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"shrl $8,%%eax\n\t"
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- "andl $1,%%eax\n":"=a"(rc)
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+ "andl $1,%%eax\n"
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+ :"=a"(rc)
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: "a"(regs)
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: "%ebx", "%ecx", "%edx", "%esi", "%edi", "memory");
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#endif
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11
kernel.spec
11
kernel.spec
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@ -656,8 +656,6 @@ Patch800: linux-2.6-crash-driver.patch
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# virt + ksm patches
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Patch1555: fix_xen_guest_on_old_EC2.patch
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# Already upstream (commit 16518d5ada690643453eb0aef3cc7841d3623c2d)
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Patch1556: kvm-fix-regression-with-cmpxchg8b-on-i386-hosts.patch
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# DRM
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Patch1801: drm-polling-fixes.patch
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@ -777,6 +775,8 @@ Patch13645: tpm-autodetect-itpm-devices.patch
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Patch13651: kvm-fix-fs-gs-reload-oops-with-invalid-ldt.patch
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Patch13652: fix-i8k-inline-asm.patch
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%endif
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BuildRoot: %{_tmppath}/kernel-%{KVERREL}-root
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@ -1322,7 +1322,6 @@ ApplyPatch linux-2.6-e1000-ich9-montevina.patch
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# Assorted Virt Fixes
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ApplyPatch fix_xen_guest_on_old_EC2.patch
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#ApplyPatch kvm-fix-regression-with-cmpxchg8b-on-i386-hosts.patch
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ApplyPatch drm-polling-fixes.patch
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ApplyPatch drm-edid-invalid.patch
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@ -1450,6 +1449,8 @@ ApplyPatch tpm-autodetect-itpm-devices.patch
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# CVE-2010-3698
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ApplyPatch kvm-fix-fs-gs-reload-oops-with-invalid-ldt.patch
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ApplyPatch fix-i8k-inline-asm.patch
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# END OF PATCH APPLICATIONS
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%endif
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@ -2036,6 +2037,10 @@ fi
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# and build.
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%changelog
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* Tue Nov 23 2010 Kyle McMartin <kyle@redhat.com>
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- fix-i8k-inline-asm.patch: backport gcc miscompilation fix from git
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[22d3243d, 6b4e81db] (rhbz#647677)
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* Mon Nov 22 2010 Jarod Wilson <jarod@redhat.com> 2.6.35.9-62
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- Linux 2.6.35.9
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- IR driver fixes from upstream
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@ -1,70 +0,0 @@
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commit 16518d5ada690643453eb0aef3cc7841d3623c2d
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Author: Avi Kivity <avi@redhat.com>
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Date: Thu Aug 26 14:31:30 2010 +0300
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KVM: x86 emulator: fix regression with cmpxchg8b on i386 hosts
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operand::val and operand::orig_val are 32-bit on i386, whereas cmpxchg8b
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operands are 64-bit.
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Fix by adding val64 and orig_val64 union members to struct operand, and
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using them where needed.
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Signed-off-by: Avi Kivity <avi@redhat.com>
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Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
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@@ -, +, @@
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arch/x86/include/asm/kvm_emulate.h | 10 +++++++++-
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arch/x86/kvm/emulate.c | 9 ++++-----
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2 files changed, 13 insertions(+), 6 deletions(-)
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--- a/arch/x86/include/asm/kvm_emulate.h
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+++ a/arch/x86/include/asm/kvm_emulate.h
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@@ -143,7 +143,15 @@ struct x86_emulate_ops {
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struct operand {
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enum { OP_REG, OP_MEM, OP_IMM, OP_NONE } type;
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unsigned int bytes;
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- unsigned long val, orig_val, *ptr;
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+ union {
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+ unsigned long orig_val;
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+ u64 orig_val64;
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+ };
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+ unsigned long *ptr;
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+ union {
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+ unsigned long val;
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+ u64 val64;
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+ };
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};
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struct fetch_cache {
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--- a/arch/x86/kvm/emulate.c
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+++ a/arch/x86/kvm/emulate.c
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@@ -1712,17 +1712,16 @@ static inline int emulate_grp9(struct x86_emulate_ctxt *ctxt,
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struct x86_emulate_ops *ops)
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{
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struct decode_cache *c = &ctxt->decode;
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- u64 old = c->dst.orig_val;
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+ u64 old = c->dst.orig_val64;
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if (((u32) (old >> 0) != (u32) c->regs[VCPU_REGS_RAX]) ||
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((u32) (old >> 32) != (u32) c->regs[VCPU_REGS_RDX])) {
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-
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c->regs[VCPU_REGS_RAX] = (u32) (old >> 0);
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c->regs[VCPU_REGS_RDX] = (u32) (old >> 32);
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ctxt->eflags &= ~EFLG_ZF;
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} else {
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- c->dst.val = ((u64)c->regs[VCPU_REGS_RCX] << 32) |
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- (u32) c->regs[VCPU_REGS_RBX];
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+ c->dst.val64 = ((u64)c->regs[VCPU_REGS_RCX] << 32) |
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+ (u32) c->regs[VCPU_REGS_RBX];
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ctxt->eflags |= EFLG_ZF;
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}
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@@ -2535,7 +2534,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
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ctxt->vcpu);
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if (rc != X86EMUL_CONTINUE)
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goto done;
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- c->src.orig_val = c->src.val;
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+ c->src.orig_val64 = c->src.val64;
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}
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if (c->src2.type == OP_MEM) {
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