clang/test/CodeGen/nullptr-arithmetic.c

   1 // RUN: %clang_cc1 -S %s -emit-llvm -o - | FileCheck %s
   2 // RUN: %clang_cc1 -S %s -emit-llvm -triple i686-unknown-unknown -o - | FileCheck %s
   3 // RUN: %clang_cc1 -S %s -emit-llvm -triple x86_64-unknown-unknown -o - | FileCheck %s
   4
   5 #include <stdint.h>
   6
   7 // This test is meant to verify code that handles the 'p = nullptr + n' idiom
   8 // used by some versions of glibc and gcc.  This is undefined behavior but
   9 // it is intended there to act like a conversion from a pointer-sized integer
  10 // to a pointer, and we would like to tolerate that.
  11
  12 #define NULLPTRI8 ((int8_t*)0)
  13
  14 // This should get the inttoptr instruction.
  15 int8_t *test1(intptr_t n) {
  16   return NULLPTRI8 + n;
  17 }
  18 // CHECK-LABEL: test1
  19 // CHECK: inttoptr
  20 // CHECK-NOT: getelementptr
  21
  22 // This doesn't meet the idiom because the element type is larger than a byte.
  23 int16_t *test2(intptr_t n) {
  24   return (int16_t*)0 + n;
  25 }
  26 // CHECK-LABEL: test2
  27 // CHECK: getelementptr
  28 // CHECK-NOT: inttoptr
  29
  30 // This doesn't meet the idiom because the offset is subtracted.
  31 int8_t* test3(intptr_t n) {
  32   return NULLPTRI8 - n;
  33 }
  34 // CHECK-LABEL: test3
  35 // CHECK: getelementptr
  36 // CHECK-NOT: inttoptr
  37
  38 // This checks the case where the offset isn't pointer-sized.
  39 // The front end will implicitly cast the offset to an integer, so we need to
  40 // make sure that doesn't cause problems on targets where integers and pointers
  41 // are not the same size.
  42 int8_t *test4(int8_t b) {
  43   return NULLPTRI8 + b;
  44 }
  45 // CHECK-LABEL: test4
  46 // CHECK: inttoptr
  47 // CHECK-NOT: getelementptr