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| author | Sanjay Patel <spatel@rotateright.com> | 2020-10-23 08:29:27 -0400 |
|---|---|---|
| committer | Sanjay Patel <spatel@rotateright.com> | 2020-10-23 08:43:45 -0400 |
| commit | 3fb0d6b0d55b52a214a3e5118dda3c7d3422782a (patch) | |
| tree | 2b667e779f1da3049ad61cd31b246a8052b363c5 /llvm/lib/Analysis/ValueTracking.cpp | |
| parent | 0351bd959faefe54456b43933b2f628ea14efb0d (diff) | |
| download | llvm-3fb0d6b0d55b52a214a3e5118dda3c7d3422782a.zip llvm-3fb0d6b0d55b52a214a3e5118dda3c7d3422782a.tar.gz llvm-3fb0d6b0d55b52a214a3e5118dda3c7d3422782a.tar.bz2 | |
[ValueTracking] add range limits for ctlz
As discussed in D89952,
instcombine can sometimes find a way to reduce similar patterns,
but it is incomplete.
InstSimplify uses the computeConstantRange() ValueTracking analysis
via simplifyICmpWithConstant(), so we just need to fill in the max
value of ctlz to process any "icmp pred ctlz(X), C" pattern (the
min value is initialized to zero automatically).
Follow-up to D89976.
Diffstat (limited to 'llvm/lib/Analysis/ValueTracking.cpp')
| -rw-r--r-- | llvm/lib/Analysis/ValueTracking.cpp | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index 7124ca8..e277b02 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -6461,7 +6461,8 @@ static void setLimitsForIntrinsic(const IntrinsicInst &II, APInt &Lower, const APInt *C; switch (II.getIntrinsicID()) { case Intrinsic::ctpop: - // Maximum of set bits is the bit width. + case Intrinsic::ctlz: + // Maximum of set/clear bits is the bit width. assert(Lower == 0 && "Expected lower bound to be zero"); Upper = Width + 1; break; |