Subzero: Validate phi instructions after CFG construction.

tests_lit/llvm2ice_tests/Input/phi-invalid.tbc

Index: tests_lit/llvm2ice_tests/Input/phi-invalid.tbc
diff --git a/tests_lit/llvm2ice_tests/Input/phi-invalid.tbc b/tests_lit/llvm2ice_tests/Input/phi-invalid.tbc
new file mode 100644
index 0000000000000000000000000000000000000000..bb9d59e0392871751f0687ff030e47c92842b205
--- /dev/null
+++ b/tests_lit/llvm2ice_tests/Input/phi-invalid.tbc
@@ -0,0 +1,55 @@
+65535,8,2;
+1,1;
+65535,17,2;
+1,5;
+7,32;
+2;
+7,1;
+21,0,1;
+21,0,1,0;
+65534;
+8,3,0,0,0;
+8,4,0,0,0;
+65535,19,2;
+5,0;
+65534;
+65535,14,2;
+1,0,76,111,111,112,67,97,114,114,105,101,100,68,101,112;
+1,1,66,97,99,107,66,114,97,110,99,104;
+65534;
+65535,12,2;
+1,2;
+65535,11,2;
+1,0;
+4,2;
+4,4;
+65534;
+2,2,1,0;
+11,1;
+43,6,0;
+16,0,2,0,3,0;
+2,1,4,0;
+11,1;
+65534;
+65535,12,2;
+1,7;
+65535,11,2;
+1,2;
+4,3;
+65534;
+11,4;
+43,7,0;
+2,2,4294967293,0;
+11,6;
+43,8,0;
+2,3,4294967293,0;
+11,6;
+2,4,4294967295,0;
+11,6;
+2,5,5,0;
+11,1,5,5;
+2,1,6,0;
+11,2,3,6;
+10;
+65534;
+65534;