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6 Commits

Author SHA1 Message Date
Yingwei Zheng
ab12bba0aa
[CGP] Drop poison-generating flags after hoisting (#90382) 
See the following case:
```
define i8 @src1(i8 %x) {
entry:
  %cmp = icmp eq i8 %x, -1
  br i1 %cmp, label %exit, label %if.then

if.then:
  %inc = add nuw nsw i8 %x, 1
  br label %exit

exit:
  %retval = phi i8 [ %inc, %if.then ], [ -1, %entry ]
  ret i8 %retval
}

define i8 @tgt1(i8 %x) {
entry:
  %inc = add nuw nsw i8 %x, 1
  %0 = icmp eq i8 %inc, 0
  br i1 %0, label %exit, label %if.then

if.then:                                          ; preds = %entry
  br label %exit

exit:                                             ; preds = %if.then, %entry
  %retval = phi i8 [ %inc, %if.then ], [ -1, %entry ]
  ret i8 %retval
}
```
`optimizeBranch` converts `icmp eq X, -1` into cmp to zero on RISC-V and
hoists the add into the entry block. Poison-generating flags should be
dropped as they don't still hold.

Proof: https://alive2.llvm.org/ce/z/sP7mvK
Fixes https://github.com/llvm/llvm-project/issues/90380
 2024-04-29 15:51:49 +08:00
Nick Anderson
f1ec0d12bb
Port CodeGenPrepare to new pass manager (and BasicBlockSectionsProfil… (#77182) 
Port CodeGenPrepare to new pass manager and dependency
BasicBlockSectionsProfileReader
Fixes: #75380

Co-authored-by: Krishna-13-cyber <84722531+Krishna-13-cyber@users.noreply.github.com>
 2024-01-09 13:32:59 +07:00
Simon Pilgrim
7648371c25 Revert 4d7c5ad58467502fcbc433591edff40d8a4d697d "[NewPM] Update CodeGenPreparePass reference in CodeGenPassBuilder (#77054)" 
Revert e0c554ad87d18dcbfcb9b6485d0da800ae1338d1 "Port CodeGenPrepare to new pass manager (and BasicBlockSectionsProfil… (#75380)"

Revert #75380 and #77054 as they were breaking EXPENSIVE_CHECKS buildbots: https://lab.llvm.org/buildbot/#/builders/104
 2024-01-05 12:28:10 +00:00
Nick Anderson
e0c554ad87
Port CodeGenPrepare to new pass manager (and BasicBlockSectionsProfil… (#75380) 
Port CodeGenPrepare to new pass manager and dependency
BasicBlockSectionsProfileReader
Fixes: #64560

Co-authored-by: Krishna-13-cyber <84722531+Krishna-13-cyber@users.noreply.github.com>
 2024-01-05 13:47:56 +07:00
David Green
dd5c52029d [CPG][ARM] Optimize towards branch on zero in codegenprepare 
This adds a simple fold into codegenprepare that converts comparison of
branches towards comparison with zero if possible. For example:
  %c = icmp ult %x, 8
  br %c, bla, blb
  %tc = lshr %x, 3
becomes
  %tc = lshr %x, 3
  %c = icmp eq %tc, 0
  br %c, bla, blb

As a first order approximation, this can reduce the number of
instructions needed to perform the branch as the shift is (often) needed
anyway. At the moment this does not effect very much, as llvm tends to
prefer the opposite form. But it can protect against regressions from
commits like rG9423f78240a2.

Simple cases of Add and Sub are added along with Shift, equally as the
comparison to zero can often be folded with cpsr flags.

Differential Revision: https://reviews.llvm.org/D101778
 2021-05-16 17:54:06 +01:00
David Green
d539357e1b [ARM] Extra branch on zero tests. NFC 2021-05-16 17:22:52 +01:00