x86: Swap destination/source to encode VEX only if possible

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Thu, Sep 13, 2018 at 5:57 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Wed, Sep 5, 2018 at 6:05 AM, Jan Beulich <JBeulich@suse.com> wrote:
>> Various moves come in load and store forms, and just like on the GPR
>> and FPU sides there would better be only one pattern. In some cases this
>> is not feasible because the opcodes are too different, but quite a few
>> cases follow a similar standard scheme. Introduce Opcode_SIMD_FloatD and
>> Opcode_SIMD_IntD, generalize handling in operand_size_match() (reverse
>> operand handling there simply needs to match "straight" operand one),
>> and fix a long standing, but so far only latent bug with when to zap
>> found_reverse_match.
>>
>> Also once again drop IgnoreSize where pointlessly applied to templates
>> touched anyway as well as *word when redundant with Reg*.
>>
>> gas/
>> 2018-09-05  Jan Beulich  <jbeulich@suse.com>
>>
>>         * config/tc-i386.c (operand_size_match): Mirror
>>         .reg/.regsimd/.acc handling from forward to reverse case.
>>         (build_vex_prefix): Check first and last operand types are equal
>>         and also consider .d for swapping operands for VEX2 encoding.
>>         (match_template): Clear found_reverse_match on every iteration.
>>         Use Opcode_SIMD_FloatD and Opcode_SIMD_IntD.
>>         * testsuite/gas/i386/pseudos.s,
>>         testsuite/gas/i386/x86-64-pseudos.s: Add kmov* tests.
>>         * testsuite/gas/i386/pseudos.d,
>>         testsuite/gas/i386/x86-64-pseudos.d: Adjust expectations.
>>
>> opcodes/
>> 2018-09-05  Jan Beulich  <jbeulich@suse.com>
>>
>>         * i386-opc.tbl (bndmov, kmovb, kmovd, kmovq, kmovw, movapd,
>>         movaps, movd, movdqa, movdqu, movhpd, movhps, movlpd, movlps,
>>         movq, movsd, movss, movupd, movups, vmovapd, vmovaps, vmovd,
>>         vmovdqa, vmovdqa32, vmovdqa64, vmovdqu, vmovdqu16, vmovdqu32,
>>         vmovdqu64, vmovdqu8, vmovq, vmovsd, vmovss, vmovupd, vmovups):
>>         Fold load and store templates where possible, adding D. Drop
>>         IgnoreSize where it was pointlessly present. Drop redundant
>>         *word.
>>         * i386-tbl.h: Re-generate.
>
> On Linux/x86-64, this caused
>
> FAIL: i386 arch 10
> FAIL: i386 arch 10 (lzcnt)
> FAIL: i386 arch 10 (prefetchw)
> FAIL: i386 arch 10 (bdver1)
> FAIL: i386 arch 10 (bdver2)
> FAIL: i386 arch 10 (bdver3)
> FAIL: i386 arch 10 (bdver4)
> FAIL: i386 arch 10 (btver1)
> FAIL: i386 arch 10 (btver2)
> FAIL: i386 noavx-1
> FAIL: i386 noavx-3
> FAIL: i386 AVX
> FAIL: i386 AVX (Intel disassembly)
> FAIL: x86-64 arch 2
> FAIL: x86-64 arch 2 (lzcnt)
> FAIL: x86-64 arch 2 (prefetchw)
> FAIL: x86-64 arch 2 (bdver1)
> FAIL: x86-64 arch 2 (bdver2)
> FAIL: x86-64 arch 2 (bdver3)
> FAIL: x86-64 arch 2 (bdver4)
> FAIL: x86-64 arch 2 (btver1)
> FAIL: x86-64 arch 2 (btver2)
> FAIL: x86-64 AVX
> FAIL: x86-64 AVX (Intel mode)
>
> Can you fix it today?
>

as fails to assemble

vzeroall

I checked in the following patch to fix it.

-- 
H.J.

From 79f0fa25b95fd82122ee76d61fded661cc3ece87 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Thu, 13 Sep 2018 06:12:31 -0700
Subject: [PATCH] x86: Swap destination/source to encode VEX only if possible

When encoding VEX, we can swap destination and source only if there are
more than 1 register operand.

	* config/tc-i386.c (build_vex_prefix): Swap destination and
	source only if there are more than 1 register operand.
---
 gas/ChangeLog        | 5 +++++
 gas/config/tc-i386.c | 7 ++++---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 7a82555a41..fc17226bb0 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,8 @@
+2018-09-13  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* config/tc-i386.c (build_vex_prefix): Swap destination and
+	source only if there are more than 1 register operand.
+
 2018-09-13  Jan Beulich  <jbeulich@suse.com>
 
 	* config/tc-i386.c (operand_size_match): Also deal with three
diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index 2bff48a778..40b458333f 100644
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -3364,9 +3364,10 @@ build_vex_prefix (const insn_template *t)
   else
     register_specifier = 0xf;
 
-  /* Use 2-byte VEX prefix by swapping destination and source
-     operand.  */
-  if (i.vec_encoding != vex_encoding_vex3
+  /* Use 2-byte VEX prefix by swapping destination and source operand
+     if there are more than 1 register operand.  */
+  if (i.reg_operands > 1
+      && i.vec_encoding != vex_encoding_vex3
       && i.dir_encoding == dir_encoding_default
       && i.operands == i.reg_operands
       && operand_type_equal (&i.types[0], &i.types[i.operands - 1])
-- 
2.17.1