[X86] Cleanup 'x' and 'y' mnemonic suffixes for vcvtpd2dq/vcvttpd2dq/vcvtpd2ps and similar instructions.

-Don't print the 'x' suffix for the 128-bit reg/mem VEX encoded instructions in Intel syntax. This is consistent with the EVEX versions.
-Don't print the 'y' suffix for the 256-bit reg/reg VEX encoded instructions in Intel or AT&T syntax. This is consistent with the EVEX versions.
-Allow the 'x' and 'y' suffixes to be used for the reg/mem forms when we're assembling using Intel syntax.
-Allow the 'x' and 'y' suffixes on the reg/reg EVEX encoded instructions in Intel or AT&T syntax. This is consistent with what VEX was already allowing.

This should fix at least some of PR28850.

llvm-svn: 286787
diff --git a/llvm/test/CodeGen/X86/combine-fcopysign.ll b/llvm/test/CodeGen/X86/combine-fcopysign.ll
index 1c559ff..807ac4e 100644
--- a/llvm/test/CodeGen/X86/combine-fcopysign.ll
+++ b/llvm/test/CodeGen/X86/combine-fcopysign.ll
@@ -315,7 +315,7 @@
 ; AVX:       # BB#0:
 ; AVX-NEXT:    vbroadcastss {{.*}}(%rip), %xmm2
 ; AVX-NEXT:    vandpd %xmm2, %xmm0, %xmm0
-; AVX-NEXT:    vcvtpd2psy %ymm1, %xmm1
+; AVX-NEXT:    vcvtpd2ps %ymm1, %xmm1
 ; AVX-NEXT:    vbroadcastss {{.*}}(%rip), %xmm2
 ; AVX-NEXT:    vandpd %xmm2, %xmm1, %xmm1
 ; AVX-NEXT:    vorpd %xmm1, %xmm0, %xmm0