[ValueTracking] Add fast path to avoid second recursive call in isKnownPositive; NFC

[goldsteinn]

Just a simple compile time improvement. This function isn't used much,
however, so its not particularly impactful.

[llvmbot]

@llvm/pr-subscribers-llvm-analysis

Author: None (goldsteinn)

Changes

Just a simple compile time improvement. This function isn't used much,
however, so its not particularly impactful.

---

Full diff: https://github.com/llvm/llvm-project/pull/83638.diff

1 Files Affected:

• (modified) llvm/lib/Analysis/ValueTracking.cpp (+5-3)

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index e591ac504e9f05..3d25585a9f9353 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -293,9 +293,11 @@ bool llvm::isKnownPositive(const Value *V, const SimplifyQuery &SQ,
   if (auto *CI = dyn_cast<ConstantInt>(V))
     return CI->getValue().isStrictlyPositive();
 
-  // TODO: We'd doing two recursive queries here.  We should factor this such
-  // that only a single query is needed.
-  return isKnownNonNegative(V, SQ, Depth) && ::isKnownNonZero(V, Depth, SQ);
+  // If `isKnownNonNegative` ever becomes more sophisticated, make sure to keep
+  // this updated.
+  KnownBits Known = computeKnownBits(V, Depth, SQ);
+  return Known.isNonNegative() &&
+         (Known.isNonZero() || ::isKnownNonZero(V, Depth, SQ));
 }
 
 bool llvm::isKnownNegative(const Value *V, const SimplifyQuery &SQ,

[dtcxzyw]

FYI https://dtcxzyw.github.io/llvm-opt-benchmark/coverage/home/dtcxzyw/llvm-project/llvm/lib/Analysis/ValueTracking.cpp.html#L291

[goldsteinn]

FYI https://dtcxzyw.github.io/llvm-opt-benchmark/coverage/home/dtcxzyw/llvm-project/llvm/lib/Analysis/ValueTracking.cpp.html#L291

Neat :)
so it will save maybe a few calls, but not much.

Edit: I'm not so attached this patch, just saw it and figured why not, but either way...

[nikic]

LGTM