[X86][test] Add encoding/decoding tests for VEX instruction w/ address-size prefix

This patch also contains a regression test for D122448

Reviewed By: hvdijk, RKSimon

Differential Revision: https://reviews.llvm.org/D122449

Author: KanRobert

llvm/test/MC/Disassembler/X86/x86-64-avx.txt

@@ -35,3 +35,6 @@
 
 # CHECK: vphsubd %xmm3, %xmm2, %xmm11
 0xc4 0x62 0xe9 0x06 0xdb
+
+# CHECK: vpsubq (%esp), %xmm1, %xmm2
+0x67 0xc5 0xf1 0xfb 0x14 0x24

llvm/test/MC/X86/x86_64-avx-encoding.s

@@ -1696,6 +1696,10 @@ vdivpd  -4(%rcx,%rbx,8), %xmm10, %xmm11
 // CHECK: encoding: [0xc5,0x19,0xfb,0x28]
           vpsubq  (%rax), %xmm12, %xmm13
 
+// CHECK: vpsubq  (%esp), %xmm1, %xmm2
+// CHECK: encoding: [0x67,0xc5,0xf1,0xfb,0x14,0x24]
+          vpsubq  (%esp), %xmm1, %xmm2
+
 // CHECK: vpsubsb  %xmm11, %xmm12, %xmm13
 // CHECK: encoding: [0xc4,0x41,0x19,0xe8,0xeb]
           vpsubsb  %xmm11, %xmm12, %xmm13