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[PowerPC] [ISEL] select x-form instruction for unaligned offset
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Authored by shchenz on May 20 2019, 10:52 PM.

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Summary

This patch is ready to fix issue like:

t50: i64 = add t44:1, Constant:i64<3>
t16: i64,ch = load<(load 8 from %ir.uglygep910.cast, !tbaa !3)> t0, t50, undef:i64

Currently we generate:

t50: i64 = ADDI8 t55:1, TargetConstant:i64<3>
t16: i64,ch = LD<Mem:(load 8 from %ir.uglygep910.cast, !tbaa !3)> TargetConstant:i64<0>, t50, t0

But this is not the best one, we should use x-form load here, like:

t46: i64 = LI8 TargetConstant:i64<3>
t18: i64,ch = LDX<Mem:(load 8 from %ir.uglygep910.cast, !tbaa !3)> t55:1, t46, t0

Because if above load is inside a loop, LI8 can be moved outside of loop in later LICM based on register pressure.

gain 10% for small case, %3 for 526.blender_r of SPEC 2017 on PWR8.

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Event Timeline

shchenz created this revision.May 20 2019, 10:52 PM
Herald added a project: Restricted Project. · View Herald TranscriptMay 20 2019, 10:52 PM
hfinkel accepted this revision.May 21 2019, 8:11 AM

LGTM

This revision is now accepted and ready to land.May 21 2019, 8:11 AM
This revision was automatically updated to reflect the committed changes.