Redefine cpu_has() to evaluate cpu features already checked in early
boot at compile time. This way the compiler might eliminate some dead code.
Signed-off-by: Andi Kleen <[email protected]>
---
include/asm-i386/cpufeature.h | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
Index: linux/include/asm-i386/cpufeature.h
===================================================================
--- linux.orig/include/asm-i386/cpufeature.h
+++ linux/include/asm-i386/cpufeature.h
@@ -106,8 +106,12 @@
#define X86_FEATURE_LAHF_LM (6*32+ 0) /* LAHF/SAHF in long mode */
#define X86_FEATURE_CMP_LEGACY (6*32+ 1) /* If yes HyperThreading not valid */
-#define cpu_has(c, bit) test_bit(bit, (c)->x86_capability)
-#define boot_cpu_has(bit) test_bit(bit, boot_cpu_data.x86_capability)
+#define cpu_has(c, bit) \
+ ((__builtin_constant_p(bit) && (bit) < 32 && \
+ (1UL << (bit)) & REQUIRED_MASK1) ? \
+ 1 : \
+ test_bit(bit, (c)->x86_capability))
+#define boot_cpu_has(bit) cpu_has(&boot_cpu_data, bit)
#define cpu_has_fpu boot_cpu_has(X86_FEATURE_FPU)
#define cpu_has_vme boot_cpu_has(X86_FEATURE_VME)
-
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