tree ffa5e52ccb7a71bd2ba075595a4f22d479e594e1
parent 35f4a9f03b133d1844f28958e0cffcba3f6c0294
author Sanjay Patel <spatel@rotateright.com> 1555540731 +0000
committer Sanjay Patel <spatel@rotateright.com> 1555540731 +0000

[x86] try to widen 'shl' as part of LEA formation

The test file has pairs of tests that are logically equivalent:
https://rise4fun.com/Alive/2zQ

%t4 = and i8 %t1, 8
%t5 = zext i8 %t4 to i16
%sh = shl i16 %t5, 2
%t6 = add i16 %sh, %t0
=>
%t4 = and i8 %t1, 8
%sh2 = shl i8 %t4, 2
%z5 = zext i8 %sh2 to i16
%t6 = add i16 %z5, %t0

...so if we can fold the shift op into LEA in the 1st pattern, then we
should be able to do the same in the 2nd pattern (unnecessary 'movzbl'
is a separate bug I think).

We don't want to do this any sooner though because that would conflict
with generic transforms that try to narrow the width of the shift.

Differential Revision: https://reviews.llvm.org/D60789

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@358622 91177308-0d34-0410-b5e6-96231b3b80d8