Implemented loose checking for potential widened loads

tests_lit/asan_tests/wideloads.ll

+; Test that potentially widened loads to not trigger an error report
+
+; REQUIRES: no_minimal_build
+
+; check for wide load exception
+; RUN: llvm-as %s -o - | pnacl-freeze > %t.pexe && %S/../../pydir/szbuild.py \
+; RUN:     --fsanitize-address --sz="-allow-externally-defined-symbols" \
+; RUN:     %t.pexe -o %t && %t | FileCheck %s --check-prefix=WIDE
+
+; check for error reporting
+; RUN: llvm-as %s -o - | pnacl-freeze > %t.pexe && %S/../../pydir/szbuild.py \
+; RUN:     --fsanitize-address --sz="-allow-externally-defined-symbols" \
+; RUN:     %t.pexe -o %t && %t 1 2>&1 | FileCheck %s --check-prefix=NOWIDE
+
+
+declare external void @exit(i32)
+
+define internal void @wide_load() {
+  %str = alloca i8, i32 1, align 1
+  %str4 = bitcast i8* %str to i32*
+  %contents = load i32, i32* %str4, align 1
+  call void @exit(i32 0)
+  unreachable
+}
+
+define internal void @no_wide_load() {
+  %str = alloca i8, i32 1, align 1
+  %straddr = ptrtoint i8* %str to i32
+  %off1addr = add i32 %straddr, 1
+  %off1 = inttoptr i32 %off1addr to i8*
+  %contents = load i8, i8* %off1, align 1
+  call void @exit(i32 1) 
+  unreachable
+}
+
+; WIDE-NOT: Illegal access
+; NOWIDE: Illegal access of 1 bytes at
+
+; use argc to determine which test routine to run
+define void @_start(i32 %arg) {
+  %argcaddr = add i32 %arg, 8
+  %argcptr = inttoptr i32 %argcaddr to i32*
+  %argc = load i32, i32* %argcptr, align 1
+  switch i32 %argc, label %error [i32 1, label %wide_load
+                                  i32 2, label %no_wide_load]
+wide_load:
+  call void @wide_load()
+  br label %error
+no_wide_load:
+  call void @no_wide_load()
+  br label %error
+error:
+  call void @exit(i32 1)
+  unreachable
+}