https://github.com/dtcxzyw closed
https://github.com/llvm/llvm-project/pull/87910
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@@ -897,7 +897,20 @@ Instruction *InstCombinerImpl::visitTrunc(TruncInst
) {
}
}
- return nullptr;
+ bool Changed = false;
+ if (!Trunc.hasNoSignedWrap() &&
+ ComputeMaxSignificantBits(Src, /*Depth=*/0, ) <= DestWidth) {
+Trunc.setHasNoSignedWrap(true);
+
https://github.com/nikic approved this pull request.
LGTM
https://github.com/llvm/llvm-project/pull/87910
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https://github.com/nikic edited https://github.com/llvm/llvm-project/pull/87910
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@@ -897,7 +897,20 @@ Instruction *InstCombinerImpl::visitTrunc(TruncInst
) {
}
}
- return nullptr;
+ bool Changed = false;
+ if (!Trunc.hasNoSignedWrap() &&
+ ComputeMaxSignificantBits(Src, /*Depth=*/0, ) <= DestWidth) {
+Trunc.setHasNoSignedWrap(true);
+
@@ -897,7 +897,20 @@ Instruction *InstCombinerImpl::visitTrunc(TruncInst
) {
}
}
- return nullptr;
+ bool Changed = false;
+ if (!Trunc.hasNoSignedWrap() &&
+ ComputeMaxSignificantBits(Src, /*Depth=*/0, ) <= DestWidth) {
+Trunc.setHasNoSignedWrap(true);
+
@@ -897,7 +897,20 @@ Instruction *InstCombinerImpl::visitTrunc(TruncInst
) {
}
}
- return nullptr;
+ bool Changed = false;
+ if (!Trunc.hasNoSignedWrap() &&
+ ComputeMaxSignificantBits(Src, /*Depth=*/0, ) <= DestWidth) {
+Trunc.setHasNoSignedWrap(true);
+
@@ -897,7 +897,20 @@ Instruction *InstCombinerImpl::visitTrunc(TruncInst
) {
}
}
- return nullptr;
+ bool Changed = false;
+ if (!Trunc.hasNoSignedWrap() &&
+ ComputeMaxSignificantBits(Src, /*Depth=*/0, ) <= DestWidth) {
+Trunc.setHasNoSignedWrap(true);
+
@@ -897,7 +897,20 @@ Instruction *InstCombinerImpl::visitTrunc(TruncInst
) {
}
}
- return nullptr;
+ bool Changed = false;
+ if (!Trunc.hasNoSignedWrap() &&
+ ComputeMaxSignificantBits(Src, /*Depth=*/0, ) <= DestWidth) {
+Trunc.setHasNoSignedWrap(true);
+
goldsteinn wrote:
LGTM.
https://github.com/llvm/llvm-project/pull/87910
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goldsteinn wrote:
Not an issue now but I think we should look into updating
`computeKnownBitsFromContext` to look use `trunc nsw/nuw` uses of `X`. If the
use is dominating / noundef, we can infer bits about `X`.
Not really an issue if we only use `KnownBits` to infer `nuw`/`nsw`, but once
we
@@ -897,7 +897,20 @@ Instruction *InstCombinerImpl::visitTrunc(TruncInst
) {
}
}
- return nullptr;
+ bool Changed = false;
+ if (!Trunc.hasNoSignedWrap() &&
+ ComputeMaxSignificantBits(Src, /*Depth=*/0, ) <= DestWidth) {
+Trunc.setHasNoSignedWrap(true);
+
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