[2/3] Temporary remove "at least 8 byte alignment" code from x86

Submitted by Denys Vlasenko on April 18, 2017, 6:30 p.m.

Details

Message ID 20170418183023.7857-3-dvlasenk@redhat.com
State New
Headers show

Commit Message

Denys Vlasenko April 18, 2017, 6:30 p.m.
This change drops forced alignment to 8 if requested alignment is higher
than 8: before the patch, -falign-functions=9 was generating

        .p2align 4,,8
        .p2align 3

which means: "align to 16 if the skip is 8 bytes or less; else align to 8".
After this change, ".p2align 3" is not emitted.

This behavior will be implemented differently by the next patch.

The new SUBALIGN_LOG define will be used by the next patch.

While we are here, avoid generating ".p2align N,,2^N-1" -
it is functionally equivalent to ".p2align N". In this case, use the latter.

2017-04-18  Denys Vlasenko  <dvlasenk@redhat.com>

    * config/i386/dragonfly.h: (ASM_OUTPUT_MAX_SKIP_ALIGN):
    Use a simpler align directive also if MAXSKIP = ALIGN-1.
    * config/i386/gas.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Likewise.
    * config/i386/lynx.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Likewise.
    * config/i386/netbsd-elf.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Likewise.
    * config/i386/i386.h (ASM_OUTPUT_MAX_SKIP_PAD): Likewise.
    * config/i386/freebsd.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Remove "If N
    is large, do at least 8 byte alignment" code. Add SUBALIGN_LOG
    define. Use a simpler align directive also if MAXSKIP = ALIGN-1.
    * config/i386/gnu-user.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Likewise.
    * config/i386/iamcu.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Likewise.
    * config/i386/openbsdelf.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Likewise.
    * config/i386/x86-64.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Likewise.

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Index: gcc/config/i386/dragonfly.h
===================================================================
--- gcc/config/i386/dragonfly.h	(revision 239860)
+++ gcc/config/i386/dragonfly.h	(working copy)
@@ -69,10 +69,12 @@  see the files COPYING3 and COPYING.RUNTIME respect
 
 #ifdef HAVE_GAS_MAX_SKIP_P2ALIGN
 #undef  ASM_OUTPUT_MAX_SKIP_ALIGN
-#define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE, LOG, MAX_SKIP)					\
-  if ((LOG) != 0) {														\
-    if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG));	\
-    else fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\
+#define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE, LOG, MAX_SKIP)			\
+  if ((LOG) != 0) {							\
+    if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))-1)			\
+      fprintf ((FILE), "\t.p2align %d\n", (LOG));			\
+    else								\
+      fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\
   }
 #endif
 
Index: gcc/config/i386/freebsd.h
===================================================================
--- gcc/config/i386/freebsd.h	(revision 239860)
+++ gcc/config/i386/freebsd.h	(working copy)
@@ -92,9 +92,9 @@  along with GCC; see the file COPYING3.  If not see
 
 /* A C statement to output to the stdio stream FILE an assembler
    command to advance the location counter to a multiple of 1<<LOG
-   bytes if it is within MAX_SKIP bytes.
+   bytes if it is within MAX_SKIP bytes.  */
 
-   This is used to align code labels according to Intel recommendations.  */
+#define SUBALIGN_LOG 3
 
 #ifdef HAVE_GAS_MAX_SKIP_P2ALIGN
 #undef  ASM_OUTPUT_MAX_SKIP_ALIGN
@@ -101,16 +101,10 @@  along with GCC; see the file COPYING3.  If not see
 #define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE,LOG,MAX_SKIP)			\
   do {									\
     if ((LOG) != 0) {							\
-      if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG));	\
-      else {								\
+      if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))-1)		\
+	fprintf ((FILE), "\t.p2align %d\n", (LOG));			\
+      else								\
 	fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\
-	/* Make sure that we have at least 8 byte alignment if > 8 byte \
-	   alignment is preferred.  */					\
-	if ((LOG) > 3							\
-	    && (1 << (LOG)) > ((MAX_SKIP) + 1)				\
-	    && (MAX_SKIP) >= 7)						\
-	  fputs ("\t.p2align 3\n", (FILE));				\
-      }									\
     }									\
   } while (0)
 #endif
Index: gcc/config/i386/gas.h
===================================================================
--- gcc/config/i386/gas.h	(revision 239860)
+++ gcc/config/i386/gas.h	(working copy)
@@ -72,10 +72,12 @@  along with GCC; see the file COPYING3.  If not see
 
 #ifdef HAVE_GAS_MAX_SKIP_P2ALIGN
 #  define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE,LOG,MAX_SKIP) \
-     if ((LOG) != 0) {\
-       if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG)); \
-       else fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP)); \
-     }
+    if ((LOG) != 0) { \
+      if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))-1)		\
+	fprintf ((FILE), "\t.p2align %d\n", (LOG));			\
+      else								\
+	fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\
+    }
 #endif
 
 /* A C statement or statements which output an assembler instruction
Index: gcc/config/i386/gnu-user.h
===================================================================
--- gcc/config/i386/gnu-user.h	(revision 239860)
+++ gcc/config/i386/gnu-user.h	(working copy)
@@ -94,24 +94,18 @@  along with GCC; see the file COPYING3.  If not see
 
 /* A C statement to output to the stdio stream FILE an assembler
    command to advance the location counter to a multiple of 1<<LOG
-   bytes if it is within MAX_SKIP bytes.
+   bytes if it is within MAX_SKIP bytes.  */
 
-   This is used to align code labels according to Intel recommendations.  */
+#define SUBALIGN_LOG 3
 
 #ifdef HAVE_GAS_MAX_SKIP_P2ALIGN
 #define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE,LOG,MAX_SKIP)			\
   do {									\
     if ((LOG) != 0) {							\
-      if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG));	\
-      else {								\
+      if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))-1)		\
+	fprintf ((FILE), "\t.p2align %d\n", (LOG));			\
+      else								\
 	fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\
-	/* Make sure that we have at least 8 byte alignment if > 8 byte \
-	   alignment is preferred.  */					\
-	if ((LOG) > 3							\
-	    && (1 << (LOG)) > ((MAX_SKIP) + 1)				\
-	    && (MAX_SKIP) >= 7)						\
-	  fputs ("\t.p2align 3\n", (FILE));				\
-      }									\
     }									\
   } while (0)
 #endif
Index: gcc/config/i386/i386.h
===================================================================
--- gcc/config/i386/i386.h	(revision 239860)
+++ gcc/config/i386/i386.h	(working copy)
@@ -2271,7 +2271,7 @@  do {									\
 #define ASM_OUTPUT_MAX_SKIP_PAD(FILE, LOG, MAX_SKIP)			\
   if ((LOG) != 0)							\
     {									\
-      if ((MAX_SKIP) == 0)						\
+      if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))-1)		\
         fprintf ((FILE), "\t.p2align %d\n", (LOG));			\
       else								\
         fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\
Index: gcc/config/i386/iamcu.h
===================================================================
--- gcc/config/i386/iamcu.h	(revision 239860)
+++ gcc/config/i386/iamcu.h	(working copy)
@@ -62,23 +62,17 @@  see the files COPYING3 and COPYING.RUNTIME respect
 
 /* A C statement to output to the stdio stream FILE an assembler
    command to advance the location counter to a multiple of 1<<LOG
-   bytes if it is within MAX_SKIP bytes.
+   bytes if it is within MAX_SKIP bytes.  */
 
-   This is used to align code labels according to Intel recommendations.  */
+#define SUBALIGN_LOG 3
 
 #define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE,LOG,MAX_SKIP)			\
   do {									\
     if ((LOG) != 0) {							\
-      if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG));	\
-      else {								\
+      if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))-1)		\
+	fprintf ((FILE), "\t.p2align %d\n", (LOG));			\
+      else								\
 	fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\
-	/* Make sure that we have at least 8 byte alignment if > 8 byte \
-	   alignment is preferred.  */					\
-	if ((LOG) > 3							\
-	    && (1 << (LOG)) > ((MAX_SKIP) + 1)				\
-	    && (MAX_SKIP) >= 7)						\
-	  fputs ("\t.p2align 3\n", (FILE));				\
-      }									\
     }									\
   } while (0)
 
Index: gcc/config/i386/lynx.h
===================================================================
--- gcc/config/i386/lynx.h	(revision 239860)
+++ gcc/config/i386/lynx.h	(working copy)
@@ -61,8 +61,10 @@  along with GCC; see the file COPYING3.  If not see
 #define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE,LOG,MAX_SKIP)			\
   do {									\
     if ((LOG) != 0) {							\
-      if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG));	\
-      else fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\
+      if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))-1)		\
+	fprintf ((FILE), "\t.p2align %d\n", (LOG));			\
+      else								\
+	fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\
     }									\
   } while (0)
 #endif
Index: gcc/config/i386/netbsd-elf.h
===================================================================
--- gcc/config/i386/netbsd-elf.h	(revision 239860)
+++ gcc/config/i386/netbsd-elf.h	(working copy)
@@ -104,8 +104,10 @@  along with GCC; see the file COPYING3.  If not see
 #ifdef HAVE_GAS_MAX_SKIP_P2ALIGN
 #define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE, LOG, MAX_SKIP)			\
   if ((LOG) != 0) {							\
-    if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG));	\
-    else fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\
+    if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))-1)			\
+      fprintf ((FILE), "\t.p2align %d\n", (LOG));			\
+    else								\
+      fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\
   }
 #endif
 
Index: gcc/config/i386/openbsdelf.h
===================================================================
--- gcc/config/i386/openbsdelf.h	(revision 239860)
+++ gcc/config/i386/openbsdelf.h	(working copy)
@@ -63,24 +63,18 @@  along with GCC; see the file COPYING3.  If not see
 
 /* A C statement to output to the stdio stream FILE an assembler
    command to advance the location counter to a multiple of 1<<LOG
-   bytes if it is within MAX_SKIP bytes.
+   bytes if it is within MAX_SKIP bytes.  */
 
-   This is used to align code labels according to Intel recommendations.  */
+#define SUBALIGN_LOG 3
 
 #ifdef HAVE_GAS_MAX_SKIP_P2ALIGN
 #define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE,LOG,MAX_SKIP)			\
   do {									\
     if ((LOG) != 0) {							\
-      if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG));	\
-      else {								\
+      if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))-1)		\
+	fprintf ((FILE), "\t.p2align %d\n", (LOG));			\
+      else								\
 	fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\
-	/* Make sure that we have at least 8 byte alignment if > 8 byte \
-	   alignment is preferred.  */					\
-	if ((LOG) > 3							\
-	    && (1 << (LOG)) > ((MAX_SKIP) + 1)				\
-	    && (MAX_SKIP) >= 7)						\
-	  fputs ("\t.p2align 3\n", (FILE));				\
-      }									\
     }									\
   } while (0)
 #endif
Index: gcc/config/i386/x86-64.h
===================================================================
--- gcc/config/i386/x86-64.h	(revision 239860)
+++ gcc/config/i386/x86-64.h	(working copy)
@@ -61,20 +61,16 @@  see the files COPYING3 and COPYING.RUNTIME respect
 
 /* This is used to align code labels according to Intel recommendations.  */
 
+#define SUBALIGN_LOG 3
+
 #ifdef HAVE_GAS_MAX_SKIP_P2ALIGN
 #define ASM_OUTPUT_MAX_SKIP_ALIGN(FILE,LOG,MAX_SKIP)			\
   do {									\
     if ((LOG) != 0) {							\
-      if ((MAX_SKIP) == 0) fprintf ((FILE), "\t.p2align %d\n", (LOG));	\
-      else {								\
+      if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))-1)		\
+	fprintf ((FILE), "\t.p2align %d\n", (LOG));			\
+      else								\
 	fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\
-	/* Make sure that we have at least 8 byte alignment if > 8 byte \
-	   alignment is preferred.  */					\
-	if ((LOG) > 3							\
-	    && (1 << (LOG)) > ((MAX_SKIP) + 1)				\
-	    && (MAX_SKIP) >= 7)						\
-	  fputs ("\t.p2align 3\n", (FILE));				\
-      }									\
     }									\
   } while (0)
 #undef  ASM_OUTPUT_MAX_SKIP_PAD
@@ -81,7 +77,7 @@  see the files COPYING3 and COPYING.RUNTIME respect
 #define ASM_OUTPUT_MAX_SKIP_PAD(FILE, LOG, MAX_SKIP)			\
   if ((LOG) != 0)							\
     {									\
-      if ((MAX_SKIP) == 0)						\
+      if ((MAX_SKIP) == 0 || (MAX_SKIP) >= (1<<(LOG))-1)		\
         fprintf ((FILE), "\t.p2align %d\n", (LOG));			\
       else								\
         fprintf ((FILE), "\t.p2align %d,,%d\n", (LOG), (MAX_SKIP));	\