llvm-project/llvm/lib/Transforms
Sanjay Patel fae900921b [InstCombine] reduce demand-limited bool math to logic
The cmp math test is inspired by memcmp() patterns seen in D75840.
I know there's at least 1 related fold we can do here if both
values are sext'd, but I'm not seeing a way to generalize further.

We have some other bool math patterns that we want to reduce, but
that might require fixing the bogus transforms noted in D72396.

Alive proof translations of the regression tests:
https://rise4fun.com/Alive/zGWi

  Name: demand add 1
  %xz = zext i1 %x to i32
  %ys = sext i1 %y to i32
  %sub = add i32 %xz, %ys
  %r = lshr i32 %sub, 31
  =>
  %notx = xor i1 %x, 1
  %and = and i1 %y, %notx
  %r = zext i1 %and to i32

  Name: demand add 2
  %xz = zext i1 %x to i5
  %ys = sext i1 %y to i5
  %sub = add i5 %xz, %ys
  %r = and i5 %sub, 16
  =>
  %notx = xor i1 %x, 1
  %and = and i1 %y, %notx
  %r = select i1 %and, i5 -16, i5 0

  Name: demand add 3
  %xz = zext i1 %x to i8
  %ys = sext i1 %y to i8
  %a = add i8 %ys, %xz
  %r = ashr i8 %a, 7
  =>
  %notx = xor i1 %x, 1
  %and = and i1 %y, %notx
  %r = sext i1 %and to i8

  Name: cmp math
  %gt = icmp ugt i32 %x, %y
  %lt = icmp ult i32 %x, %y
  %xz = zext i1 %gt to i32
  %yz = zext i1 %lt to i32
  %s = sub i32 %xz, %yz
  %r = lshr i32 %s, 31
  =>
  %r = zext i1 %lt to i32

Differential Revision: https://reviews.llvm.org/D75961
2020-03-11 15:45:58 -04:00
..
AggressiveInstCombine [ConstantFolding] Always return something from ConstantFoldConstant 2020-03-04 18:24:47 +01:00
CFGuard Add missing newlines at EOF; NFC 2020-02-12 15:57:25 +00:00
Coroutines [Coroutines] Optimized coroutine elision based on reachability 2020-03-05 14:43:50 +08:00
Hello Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
IPO [WPD] Provide a way to prevent functions from being devirtualized 2020-03-09 14:05:15 +03:00
InstCombine [InstCombine] reduce demand-limited bool math to logic 2020-03-11 15:45:58 -04:00
Instrumentation Reland: [Coverage] Revise format to reduce binary size 2020-02-28 18:12:04 -08:00
ObjCARC [ObjC][ARC] Don't remove autoreleaseRV/retainRV pairs if the call isn't 2020-03-09 13:21:38 -07:00
Scalar [Matrix] Add remark propagation along the inlined-at chain. 2020-03-11 17:40:08 +00:00
Utils [SimplifyLibcalls] Don't replace locked IO (fgetc/fgets/fputc/fputs/fread/fwrite) with unlocked IO (*_unlocked) 2020-03-10 11:11:58 -07:00
Vectorize [TTI][ARM][MVE] Refine gather/scatter cost model 2020-03-11 10:23:41 +00:00
CMakeLists.txt Add Windows Control Flow Guard checks (/guard:cf). 2019-10-28 15:19:39 +00:00
LLVMBuild.txt Add Windows Control Flow Guard checks (/guard:cf). 2019-10-28 15:19:39 +00:00