diff options
Diffstat (limited to 'lib/Target/README.txt')
| -rw-r--r-- | lib/Target/README.txt | 21 |
1 files changed, 1 insertions, 20 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index 5c97b8984c..abb8ee6f49 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -74,26 +74,7 @@ This has a number of uses: //===---------------------------------------------------------------------===// We should recognized various "overflow detection" idioms and translate them into -llvm.uadd.with.overflow and similar intrinsics. For example, we compile this: - -size_t add(size_t a,size_t b) { - if (a+b<a) - exit(0); - return a+b; -} - -into: - - addq %rdi, %rbx - cmpq %rdi, %rbx - jae LBB0_2 - -when it would be better to generate: - - addq %rdi, %rbx - jno LBB0_2 - -Apparently some version of GCC knows this. Here is a multiply idiom: +llvm.uadd.with.overflow and similar intrinsics. Here is a multiply idiom: unsigned int mul(unsigned int a,unsigned int b) { if ((unsigned long long)a*b>0xffffffff) |