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x86/APX: squash REX prefix when REX2 is being emitted

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We should not (silently) emit a REX prefix ahead of a REX2-encoded insn;
such encodings are illegal. Best we can do is fold the REX bits into the
REX2 prefix, and then zap the REX one from i.prefix[].
This commit is contained in:
Jan Beulich 2024-10-30 12:12:24 +01:00
parent 0a81e17f76
commit d0a9378d98
3 changed files with 13 additions and 1 deletions
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4
gas/config/tc-i386.c
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@ -4527,7 +4527,8 @@ build_rex2_prefix (void)
i.vex.bytes[0] = 0xd5;
/* For the W R X B bits, the variables of rex prefix will be reused. */
i.vex.bytes[1] = ((i.tm.opcode_space << 7)
| (i.rex2 << 4) | i.rex);
| (i.rex2 << 4)
| ((i.rex | i.prefix[REX_PREFIX]) & 0xf));
}
/* Build the EVEX prefix (4-byte) for evex insn
@ -4676,6 +4677,7 @@ static void establish_rex (void)
build_rex2_prefix ();
/* The individual REX.RXBW bits got consumed. */
i.rex &= REX_OPCODE;
i.prefix[REX_PREFIX] = 0;
}
else if (i.rex != 0)
add_prefix (REX_OPCODE | i.rex);

4
gas/testsuite/gas/i386/x86-64-apx-rex2.d
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@ -80,4 +80,8 @@ Disassembly of section .text:
[ ]*[a-f0-9]+:[ ]*d5 76 8d 7c 20 01 lea 0x1\(%r16,%r28,1\),%r31d
[ ]*[a-f0-9]+:[ ]*d5 12 8d 84 04 81 00 00 00 lea 0x81\(%r20,%r8,1\),%eax
[ ]*[a-f0-9]+:[ ]*d5 57 8d bc 04 81 00 00 00 lea 0x81\(%r28,%r8,1\),%r31d
[ ]*[a-f0-9]+:[ ]*d5 14 f7 14 24 \{rex2 0x14\} notl \(%r20\)
[ ]*[a-f0-9]+:[ ]*d5 12 f7 14 24 notl \(%r20,%r12,1\)
[ ]*[a-f0-9]+:[ ]*d5 11 f7 14 24 notl \(%r28\)
[ ]*[a-f0-9]+:[ ]*d5 18 f7 14 24 notq \(%r20\)
#pass

6
gas/testsuite/gas/i386/x86-64-apx-rex2.s
View File

@ -83,3 +83,9 @@ _start:
leal 1(%r16, %r28), %r31d
leal 129(%r20, %r8), %eax
leal 129(%r28, %r8), %r31d
## explicit REX prefix
rex.r notl (%r20)
rex.x notl (%r20)
rex.b notl (%r20)
rex.w not (%r20)