[PATCH] D67799: [InstCombine] Fold a shifty implementation of clamp0.

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp:1933-1936
+    if (match(&I, m_c_And(m_Value(Shift), m_Value(V))) &&
+        match(Shift,
+              m_OneUse(m_AShr(m_OneUse(m_NSWSub(m_Zero(), m_Specific(V))),
+                              m_APInt(ShAmt)))) &&
----------------
1. Only `m_AShr` has to be one-use
2. This doesn't actually deal with commutativity correctly

You want
```
match(&I, m_c_And(m_OneUse(m_AShr(m_NSWSub(m_Zero(),
                                           m_Specific(V)),
                                  m_APInt(ShAmt))),
                  m_Value(V)))
```


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D67799/new/

https://reviews.llvm.org/D67799