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* [DAGCombiner] fold shift-trunc-shift to shift-mask-trunc (2nd try)Sanjay Patel2019-12-131-2/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The initial attempt (rG89633320) botched the logic by reversing the source/dest types. Added x86 tests for additional coverage. The vector tests show a potential improvement (fold vector load instead of broadcasting), but that's a known/existing problem. This fold is done in IR by instcombine, and we have a special form of it already here in DAGCombiner, but we want the more general transform too: https://rise4fun.com/Alive/3jZm Name: general Pre: (C1 + zext(C2) < 64) %s = lshr i64 %x, C1 %t = trunc i64 %s to i16 %r = lshr i16 %t, C2 => %s2 = lshr i64 %x, C1 + zext(C2) %a = and i64 %s2, zext((1 << (16 - C2)) - 1) %r = trunc %a to i16 Name: special Pre: C1 == 48 %s = lshr i64 %x, C1 %t = trunc i64 %s to i16 %r = lshr i16 %t, C2 => %s2 = lshr i64 %x, C1 + zext(C2) %r = trunc %s2 to i16 ...because D58017 exposes a regression without this fold.
* Revert "[DAGCombiner] fold shift-trunc-shift to shift-mask-trunc"Sanjay Patel2019-12-121-1/+2
| | | | | This reverts commit 8963332c3327daa652ba3e26d35f9109b6991985. There was a logic bug typo in this code, but it wasn't visible in the asm for the tests.
* [DAGCombiner] fold shift-trunc-shift to shift-mask-truncSanjay Patel2019-12-121-2/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | This fold is done in IR by instcombine, and we have a special form of it already here in DAGCombiner, but we want the more general transform too: https://rise4fun.com/Alive/3jZm Name: general Pre: (C1 + zext(C2) < 64) %s = lshr i64 %x, C1 %t = trunc i64 %s to i16 %r = lshr i16 %t, C2 => %s2 = lshr i64 %x, C1 + zext(C2) %a = and i64 %s2, zext((1 << (16 - C2)) - 1) %r = trunc %a to i16 Name: special Pre: C1 == 48 %s = lshr i64 %x, C1 %t = trunc i64 %s to i16 %r = lshr i16 %t, C2 => %s2 = lshr i64 %x, C1 + zext(C2) %r = trunc %s2 to i16 ...because D58017 exposes a regression without this fold.
* [AArch64][PowerPC] add tests for shift sandwich; NFCSanjay Patel2019-12-121-3/+20
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* [DAGCombine] Improve ReduceLoad for SRLSam Parker2018-04-091-0/+18
Recommitting r329283, third time lucky... If the SRL node is only used by an AND, we may be able to set the ExtVT to the width of the mask, making the AND redundant. To support this, another check has been added in isLegalNarrowLoad which queries whether the load is valid. Differential Revision: https://reviews.llvm.org/D41350 llvm-svn: 329551
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