[X86][Asm] Allow negative immediate to appear before bracketed expression

[coby]

Summary

Currently, only non-negative immediate is allowed prior to a brac expression (memory reference).
MASM / GAS does not have any problem cope with the left side of the real line, so we should be able to as well.

llvm: D36229

[rnk]

Looks good

cfe/trunk/test/CodeGen/ms-inline-asm.c

 // CHECK: mov eax, $$12
   __asm mov eax, 4 + 8 * 16
 // CHECK: mov eax, $$132
   __asm mov eax, -4 + 8 * 16
 // CHECK: mov eax, $$124
   __asm mov eax, (4 + 4) * 16
 // CHECK: mov eax, $$128
   __asm mov eax, 4 + 8 * -16
-// CHECK: mov eax, $$4294967172
+// CHECK: mov eax, $$-124
   __asm mov eax, 4 + 16 / -8
 // CHECK: mov eax, $$2
   __asm mov eax, (16 + 16) / -8
-// CHECK: mov eax, $$4294967292
+// CHECK: mov eax, $$-4
   __asm mov eax, ~15
-// CHECK: mov eax, $$4294967280
+// CHECK: mov eax, $$-16
   __asm mov eax, 6 ^ 3
 // CHECK: mov eax, $$5
 // CHECK: "~{eax},~{dirflag},~{fpsr},~{flags}"()
 }
 
 void t38() {
 // CHECK: t38
   int arr[4];
__asm {
     mov dr2, ebx
     mov dr3, ecx
     mov dr6, edx
     mov dr7, ecx
   }
   // CHECK: call void asm sideeffect inteldialect "mov dr0, eax\0A\09mov dr1, ebx\0A\09mov dr2, ebx\0A\09mov dr3, ecx\0A\09mov dr6, edx\0A\09mov dr7, ecx", "~{dr0},~{dr1},~{dr2},~{dr3},~{dr6},~{dr7},~{dirflag},~{fpsr},~{flags}"()
 }
 
+void t46() {
+  // CHECK-LABEL: define void @t46
+  __asm add eax, -128[eax]
+  // CHECK: call void asm sideeffect inteldialect "add eax, $$-128[eax]", "~{eax},~{flags},~{dirflag},~{fpsr},~{flags}"()
+}
+
 void dot_operator(){
 // CHECK-LABEL: define void @dot_operator
   __asm { mov eax, 3[ebx]A.b}
 // CHECK: call void asm sideeffect inteldialect "mov eax, $$3[ebx].4", "~{eax},~{dirflag},~{fpsr},~{flags}"
 }
 
 void call_clobber() {
   __asm call t41