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3 Commits

Author SHA1 Message Date
Sanjay Patel
74c7fb002f [CodeGen] use nsw negation for builtin abs 
The clang builtins have the same semantics as the stdlib functions.
The stdlib functions are defined in section 7.20.6.1 of the C standard with:
"If the result cannot be represented, the behavior is undefined."

That lets us mark the negation with 'nsw' because "sub i32 0, INT_MIN" would
be UB/poison.

Differential Revision: https://reviews.llvm.org/D47202

llvm-svn: 333038
 2018-05-22 23:02:13 +00:00
Sanjay Patel
1ff6b27940 [CodeGen] produce the LLVM canonical form of abs 
We chose the 'slt' form as canonical in IR with:
rL332819
...so we should generate that form directly for efficiency.

llvm-svn: 332989
 2018-05-22 15:36:50 +00:00
Sanjay Patel
b6e5d4ead1 [CodeGen] add tests for abs builtins; NFC 
llvm-svn: 332988
 2018-05-22 15:11:59 +00:00