commit f238d270732214f8f87d086ce50b68e770c05e47
author Fangrui Song <maskray@google.com> Fri Apr 19 02:06:06 2019 +0000
committer Fangrui Song <maskray@google.com> Fri Apr 19 02:06:06 2019 +0000
tree ce7b6bf9223fda7770166a523469cf76542d88a4
parent 667d4f41076c8eecf56aa6a4695575183948e116

[APInt] Optimize umul_ov

Change two costly udiv() calls to lshr(1)*RHS + left-shift + plus

On one 64-bit umul_ov benchmark, I measured an obvious improvement: 12.8129s -> 3.6257s

Note, there may be some value to special case 64-bit (the most common
case) with __builtin_umulll_overflow().

Differential Revision: https://reviews.llvm.org/D60669

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@358730 91177308-0d34-0410-b5e6-96231b3b80d8