Add trap codes to the Cretonne IL.

The trap and trapz/trapnz instructions now take a trap code immediate
operand which indicates the reason for trapping.

cranelift/filetests/isa/intel/binary32.cton

@@ -369,5 +369,5 @@ ebb1:
 
     ; asm: ebb2:
 ebb2:
-    trap                                        ; bin: 0f 0b
+    trap user0                                  ; bin: 0f 0b
 }

cranelift/filetests/isa/intel/binary64.cton

@@ -861,5 +861,5 @@ ebb0:
     ; asm: movl %r10d, %ecx
     [-,%rcx]            v32 = uextend.i64 v13           ; bin: 44 89 d1
 
-    trap                                                ; bin: 0f 0b
+    trap user0                                          ; bin: 0f 0b
 }

cranelift/filetests/isa/intel/legalize-custom.cton

@@ -9,22 +9,22 @@ isa intel
 
 function %cond_trap(i32) {
 ebb0(v1: i32):
-    trapz v1
+    trapz v1, user67
     return
     ; check: $ebb0($v1: i32):
     ; nextln: brnz $v1, $(new=$EBB)
-    ; nextln: trap
+    ; nextln: trap user67
     ; check: $new:
     ; nextln: return
 }
 
 function %cond_trap2(i32) {
 ebb0(v1: i32):
-    trapnz v1
+    trapnz v1, int_ovf
     return
     ; check: $ebb0($v1: i32):
     ; nextln: brz $v1, $(new=$EBB)
-    ; nextln: trap
+    ; nextln: trap int_ovf
     ; check: $new:
     ; nextln: return
 }
@@ -32,11 +32,11 @@ ebb0(v1: i32):
 function %cond_trap_b1(i32) {
 ebb0(v1: i32):
     v2 = icmp_imm eq v1, 6
-    trapz v2
+    trapz v2, user7
     return
     ; check: $ebb0($v1: i32):
     ; check: brnz $v2, $(new=$EBB)
-    ; nextln: trap
+    ; nextln: trap user7
     ; check: $new:
     ; nextln: return
 }
@@ -44,11 +44,11 @@ ebb0(v1: i32):
 function %cond_trap2_b1(i32) {
 ebb0(v1: i32):
     v2 = icmp_imm eq v1, 6
-    trapnz v2
+    trapnz v2, user9
     return
     ; check: $ebb0($v1: i32):
     ; check: brz $v2, $(new=$EBB)
-    ; nextln: trap
+    ; nextln: trap user9
     ; check: $new:
     ; nextln: return
 }

cranelift/filetests/isa/intel/legalize-memory.cton

@@ -64,7 +64,7 @@ ebb0(v0: i32, v999: i64):
     ; Boundscheck code
     ; check: $(oob=$V) = icmp
     ; nextln: brz $oob, $(ok=$EBB)
-    ; nextln: trap
+    ; nextln: trap heap_oob
     ; check: $ok:
     ; Checks here are assuming that no pipehole opts fold the load offsets.
     ; nextln: $(xoff=$V) = uextend.i64 $v0