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[PATCH] x86: Rewrite NOP generation for fill and alignment

From: "H.J. Lu" <hongjiu dot lu at intel dot com>
To: binutils at sourceware dot org, Martin Liska <mliska at suse dot cz>
Date: Thu, 1 Mar 2018 05:56:01 -0800
Subject: [PATCH] x86: Rewrite NOP generation for fill and alignment
Authentication-results: sourceware.org; auth=none
Reply-to: "H.J. Lu" <hjl dot tools at gmail dot com>

Sorry if you get this email twice.  The first one may be too large for
binutils mailing list.  It is also at

https://github.com/hjl-tools/binutils-gdb/commit/df9716667487e6df69264dd976ec7a3451433e3c

Rewrite NOP generation for fill and code alignment by:

1. Add a 11-byte NOP with another 0x66 prefix.
2. Remove the multi-byte NOP entries which consist of 2 instructions.
3. Select proper NOPs based on ISA and processor tuning.
4. Generate multiple NOPs with the longer NOPs first followed by the
shorter NOP.
5. Use jump for larger NOP padding:
   a. > 8 bytes (2 NOPs) in 16-bit mode.
   b. > 14 bytes (2 NOPs) for older processors.
   c. > 77 bytes (7 NOPs) for newer processors.
6. Update MAX_MEM_FOR_RS_ALIGN_CODE to 4095.

Any comments?

H.J.
	PR gas/22874
	* config/tc-i386.c (f32_5): Removed.
	(f32_8): Likewise.
	(f32_9): Likewise.
	(f32_10): Likewise.
	(f32_11): Likewise.
	(f32_12): Likewise.
	(f32_13): Likewise.
	(f32_14): Likewise.
	(f16_5): Likewise.
	(f16_6): Likewise.
	(f16_7): Likewise.
	(f16_8): Likewise.
	(jump_31): Likewise.
	(alt64_11): Likewise.
	(alt64_patt): Likewise.
	(jump_disp8): New.
	(jump32_disp32): Likewise.
	(jump16_disp32): Likewise.
	(alt_11): Likewise.
	(f32_patt): Updated.
	(f16_patt): Likewise.
	(alt_patt): Add alt_11.
	(i386_align_code): Merged with ...
	(i386_generate_nops): This.  Rewritten.
	(fits_in_imm7): Moved before i386_generate_nops.
	(fits_in_imm31): Likewise.
	* config/tc-i386.h (MAX_MEM_FOR_RS_ALIGN_CODE): Updated to
	4095.
	(i386_align_code): Removed.
	(HANDLE_ALIGN): Rewritten with i386_generate_nops.
	* doc/as.texinfo: Update limits of control byte for x86 .nops
	directive.
	* testsuite/gas/i386/i386.exp: Run nops-7 and x86-64-nops-7.
	* gas/testsuite/gas/i386/noavx-3.l: Updated.
	* gas/testsuite/gas/i386/nop-1.d: Likewise.
	* gas/testsuite/gas/i386/nop-1.s: Likewise.
	* gas/testsuite/gas/i386/nop-2.d: Likewise.
	* gas/testsuite/gas/i386/nop-2.s: Likewise.
	* gas/testsuite/gas/i386/nop-3.d: Likewise.
	* gas/testsuite/gas/i386/nop-4.d: Likewise.
	* gas/testsuite/gas/i386/nop-5.d: Likewise.
	* gas/testsuite/gas/i386/nop-5.s: Likewise.
	* gas/testsuite/gas/i386/nop-6.d: Likewise.
	* gas/testsuite/gas/i386/nop-bad-1.l: Likewise.
	* gas/testsuite/gas/i386/nops-1-core2.d: Likewise.
	* gas/testsuite/gas/i386/nops-1-i386-i686.d: Likewise.
	* gas/testsuite/gas/i386/nops-1-i386.d: Likewise.
	* gas/testsuite/gas/i386/nops-1-i686.d: Likewise.
	* gas/testsuite/gas/i386/nops-1-k8.d: Likewise.
	* gas/testsuite/gas/i386/nops-1.d: Likewise.
	* gas/testsuite/gas/i386/nops-2-core2.d: Likewise.
	* gas/testsuite/gas/i386/nops-2-i386.d: Likewise.
	* gas/testsuite/gas/i386/nops-2.d: Likewise.
	* gas/testsuite/gas/i386/nops-3-i386.d: Likewise.
	* gas/testsuite/gas/i386/nops-3-i686.d: Likewise.
	* gas/testsuite/gas/i386/nops-3.d: Likewise.
	* gas/testsuite/gas/i386/nops-4-i386.d: Likewise.
	* gas/testsuite/gas/i386/nops-4-i686.d: Likewise.
	* gas/testsuite/gas/i386/nops-4.d: Likewise.
	* gas/testsuite/gas/i386/nops-4a-i686.d: Likewise.
	* gas/testsuite/gas/i386/nops-5-i686.d: Likewise.
	* gas/testsuite/gas/i386/nops-5.d: Likewise.
	* gas/testsuite/gas/i386/nops-6.d: Likewise.
	* gas/testsuite/gas/i386/nops16-1.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nop-1.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nop-2.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nop-5.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nops-1-core2.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nops-1-g64.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nops-1-k8.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nops-1-pentium.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nops-1.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nops-2.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nops-3.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nops-4-core2.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nops-4-k8.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nops-4.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nops-5-k8.d: Likewise.
	* gas/testsuite/gas/i386/x86-64-nops-5.d: Likewise.
	* gas/testsuite/gas/i386/ilp32/x86-64-nops-1-core2.d: Likewise.
	* gas/testsuite/gas/i386/ilp32/x86-64-nops-1-k8.d: Likewise.
	* gas/testsuite/gas/i386/ilp32/x86-64-nops-1-pentium.d: Likewise.
	* gas/testsuite/gas/i386/ilp32/x86-64-nops-1.d: Likewise.
	* gas/testsuite/gas/i386/ilp32/x86-64-nops-2.d: Likewise.
	* gas/testsuite/gas/i386/ilp32/x86-64-nops-3.d: Likewise.
	* gas/testsuite/gas/i386/ilp32/x86-64-nops-4-core2.d: Likewise.
	* gas/testsuite/gas/i386/ilp32/x86-64-nops-4-k8.d: Likewise.
	* gas/testsuite/gas/i386/ilp32/x86-64-nops-4.d: Likewise.
	* gas/testsuite/gas/i386/ilp32/x86-64-nops-5-k8.d: Likewise.
	* gas/testsuite/gas/i386/ilp32/x86-64-nops-5.d: Likewise.
	* gas/testsuite/gas/i386/nops-7.d: New file.
	* gas/testsuite/gas/i386/nops-7.s: Likewise.
	* gas/testsuite/gas/i386/x86-64-nops-7.d: Likewise.

Attachment: 0001-x86-Rewrite-NOP-generation-for-fill-and-alignment.patch.xz
Description: application/xz

Follow-Ups:
- Re: [PATCH] x86: Rewrite NOP generation for fill and alignment
  - From: H.J. Lu

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