x86 asm: logical instructions move from x86-assembly-cheat

README.adoc

@@ -12366,6 +12366,15 @@ Bibliography:
 ** link:userland/arch/x86_64/idiv.S[IDIV]
 * link:userland/arch/x86_64/cmp.S[CMP]
 
+=== x86 logical instructions
+
+<<intel-manual-1>> 5.1.4 "Logical Instructions"
+
+* link:userland/arch/x86_64/and.S[AND]
+* link:userland/arch/x86_64/not.S[NOT]
+* link:userland/arch/x86_64/or.S[OR]
+* link:userland/arch/x86_64/xor.S[XOR]
+
 === x86 SIMD
 
 History:

userland/arch/x86_64/and.S

@@ -0,0 +1,9 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#x86-logical-instructions */
+
+#include <lkmc.h>
+
+LKMC_PROLOGUE
+    mov $0x00FF, %rax
+    and $0x0F0F, %rax
+    LKMC_ASSERT_EQ(%rax, $0x000F)
+LKMC_EPILOGUE

userland/arch/x86_64/not.S

@@ -0,0 +1,9 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#x86-logical-instructions */
+
+#include <lkmc.h>
+
+LKMC_PROLOGUE
+    mov $0x0FF0, %rax
+    not %ax
+    LKMC_ASSERT_EQ(%rax, $0xF00F)
+LKMC_EPILOGUE

userland/arch/x86_64/or.S

@@ -0,0 +1,9 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#x86-logical-instructions */
+
+#include <lkmc.h>
+
+LKMC_PROLOGUE
+    mov $0x00FF, %rax
+    or $0x0F0F, %ax
+    LKMC_ASSERT_EQ(%rax, $0x0FFF)
+LKMC_EPILOGUE

userland/arch/x86_64/xor.S

@@ -0,0 +1,22 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#x86-logical-instructions */
+
+#include <lkmc.h>
+
+LKMC_PROLOGUE
+    mov $0x00FF, %rax
+    xor $0x0F0F, %ax
+    LKMC_ASSERT_EQ(%rax, $0x0FF0)
+
+    /* xor to set to zero idiom
+     *
+     * http://stackoverflow.com/questions/1135679/does-using-xor-reg-reg-give-advantage-over-mov-reg-0
+     *
+     * xor can be used to set a register to 0 instad of mov:
+     *
+     * Compileres often do this to generate shorter instrucitons,
+     * but there are also cases where `mov` is better.
+     */
+    mov $0x1020, %rax
+    xor %ax, %ax
+    mov $0x0000, %ax
+LKMC_EPILOGUE