Fix bugs in cpuid.h.

This commit makes two changes:

- Remove the push and pop instructions that were saving and restoring %ebx
  before and after cpuid in 32-bit pic mode. We were doing this to ensure we
  don't lose the GOT address in pic register %ebx, but this isn't necessary
  because the GOT address is kept in a virtual register.

- In 64-bit mode, preserve base register %rbx around cpuid.

This fixes PR20311 and rdar://problem/17686779.

llvm-svn: 218173

1 files changed, 18 insertions, 0 deletions

diff --git a/clang/test/Headers/cpuid.c b/clang/test/Headers/cpuid.c
new file mode 100644
index 00000000000..b0ba07af2f2
--- /dev/null
+++ b/clang/test/Headers/cpuid.c
@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 %s -ffreestanding -triple x86_64-apple-darwin -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-64
+// RUN: %clang_cc1 %s -ffreestanding -triple i386 -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-32
+
+#include <cpuid.h>
+
+// CHECK-64: {{.*}} call { i32, i32, i32, i32 } asm "  xchgq  %rbx,${1:q}\0A cpuid\0A xchgq %rbx,${1:q}", "={ax},=r,={cx},={dx},0,~{dirflag},~{fpsr},~{flags}"(i32 %{{[a-z0-9]+}})
+// CHECK-64: {{.*}} call { i32, i32, i32, i32 } asm "  xchgq  %rbx,${1:q}\0A  cpuid\0A  xchgq  %rbx,${1:q}", "={ax},=r,={cx},={dx},0,2,~{dirflag},~{fpsr},~{flags}"(i32 %{{[a-z0-9]+}}, i32 %{{[a-z0-9]+}})
+
+// CHECK-32: {{.*}} call { i32, i32, i32, i32 } asm "cpuid", "={ax},={bx},={cx},={dx},0,~{dirflag},~{fpsr},~{flags}"(i32 %{{[a-z0-9]+}})
+// CHECK-32: {{.*}} call { i32, i32, i32, i32 } asm "cpuid", "={ax},={bx},={cx},={dx},0,2,~{dirflag},~{fpsr},~{flags}"(i32 %{{[a-z0-9]+}}, i32 %{{[a-z0-9]+}})
+
+unsigned eax0, ebx0, ecx0, edx0;
+unsigned eax1, ebx1, ecx1, edx1;
+
+void test_cpuid(unsigned level, unsigned count) {
+  __cpuid(level, eax1, ebx1, ecx1, edx1);
+  __cpuid_count(level, count, eax0, ebx0, ecx0, edx0);
+}