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[InstCombine] Fold icmp of trunc nuw/nsw #90436

Closed nikic closed 1 week ago

nikic commented 2 weeks ago

Convert the existing foldICmpTruncWithTruncOrExt() fold to work with trunc nowrap flags instead of computeKnownBits(). This also allows us to generalize the fold to work with signed comparisons.

Interestingly, apart from the obvious combinations like signed predicates with trunc nsw, some non-obvious ones are also legal. For example for unsigned predicates we can do the transform for two trunc nsw as well (rather than only trunc nuw).

Proofs: https://alive2.llvm.org/ce/z/ndewwK

llvmbot commented 2 weeks ago

@llvm/pr-subscribers-llvm-ir

Author: Nikita Popov (nikic)

Changes Convert the existing foldICmpTruncWithTruncOrExt() fold to work with trunc nowrap flags instead of computeKnownBits(). This also allows us to generalize the fold to work with signed comparisons. Interestingly, apart from the obvious combinations like signed predicates with trunc nsw, some non-obvious ones are also legal. For example for unsigned predicates we can do the transform for two trunc nsw as well (rather than only trunc nuw). Proofs: https://alive2.llvm.org/ce/z/ndewwK --- Full diff: https://github.com/llvm/llvm-project/pull/90436.diff 3 Files Affected: - (modified) llvm/include/llvm/IR/PatternMatch.h (+27) - (modified) llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp (+30-25) - (modified) llvm/test/Transforms/InstCombine/icmp-of-trunc-ext.ll (+26-51) ``````````diff diff --git a/llvm/include/llvm/IR/PatternMatch.h b/llvm/include/llvm/IR/PatternMatch.h index 0b13b4aad9c326..f063e6531dda4f 100644 --- a/llvm/include/llvm/IR/PatternMatch.h +++ b/llvm/include/llvm/IR/PatternMatch.h @@ -1839,6 +1839,19 @@ template struct NNegZExt_match { } }; +template struct NoWrapTrunc_match { + Op_t Op; + + NoWrapTrunc_match(const Op_t &OpMatch) : Op(OpMatch) {} + + template bool match(OpTy *V) { + if (auto *I = dyn_cast(V)) + return (I->getNoWrapKind() & WrapFlags) == WrapFlags && + Op.match(I->getOperand(0)); + return false; + } +}; + /// Matches BitCast. template inline CastOperator_match @@ -1900,6 +1913,20 @@ inline CastOperator_match m_Trunc(const OpTy &Op) { return CastOperator_match(Op); } +/// Matches trunc nuw. +template +inline NoWrapTrunc_match +m_NUWTrunc(const OpTy &Op) { + return NoWrapTrunc_match(Op); +} + +/// Matches trunc nsw. +template +inline NoWrapTrunc_match +m_NSWTrunc(const OpTy &Op) { + return NoWrapTrunc_match(Op); +} + template inline match_combine_or, OpTy> m_TruncOrSelf(const OpTy &Op) { diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index 1064340cb53661..317b3aef40a97c 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -1479,19 +1479,29 @@ Instruction *InstCombinerImpl::foldICmpTruncConstant(ICmpInst &Cmp, return nullptr; } -/// Fold icmp (trunc X), (trunc Y). -/// Fold icmp (trunc X), (zext Y). +/// Fold icmp (trunc nuw/nsw X), (trunc nuw/nsw Y). +/// Fold icmp (trunc nuw/nsw X), (zext/sext Y). Instruction * InstCombinerImpl::foldICmpTruncWithTruncOrExt(ICmpInst &Cmp, const SimplifyQuery &Q) { - if (Cmp.isSigned()) - return nullptr; - Value *X, *Y; ICmpInst::Predicate Pred; - bool YIsZext = false; + bool YIsSExt = false; // Try to match icmp (trunc X), (trunc Y) if (match(&Cmp, m_ICmp(Pred, m_Trunc(m_Value(X)), m_Trunc(m_Value(Y))))) { + unsigned NoWrapFlags = cast(Cmp.getOperand(0))->getNoWrapKind() & + cast(Cmp.getOperand(1))->getNoWrapKind(); + if (Cmp.isSigned()) { + // For signed comparisons, both truncs must be nsw. + if (!(NoWrapFlags & TruncInst::NoSignedWrap)) + return nullptr; + } else { + // For unsigned and equality comparisons, either both must be nuw or + // both must be nsw, we don't care which. + if (!NoWrapFlags) + return nullptr; + } + if (X->getType() != Y->getType() && (!Cmp.getOperand(0)->hasOneUse() || !Cmp.getOperand(1)->hasOneUse())) return nullptr; @@ -1501,12 +1511,19 @@ InstCombinerImpl::foldICmpTruncWithTruncOrExt(ICmpInst &Cmp, Pred = Cmp.getSwappedPredicate(Pred); } } - // Try to match icmp (trunc X), (zext Y) - else if (match(&Cmp, m_c_ICmp(Pred, m_Trunc(m_Value(X)), - m_OneUse(m_ZExt(m_Value(Y)))))) - - YIsZext = true; - else + // Try to match icmp (trunc nuw X), (zext Y) + else if (!Cmp.isSigned() && + match(&Cmp, m_c_ICmp(Pred, m_NUWTrunc(m_Value(X)), + m_OneUse(m_ZExt(m_Value(Y)))))) { + // Can fold trunc nuw + zext for unsigned and equality predicates. + } + // Try to match icmp (trunc nsw X), (sext Y) + else if (match(&Cmp, m_c_ICmp(Pred, m_NSWTrunc(m_Value(X)), + m_OneUse(m_ZExtOrSExt(m_Value(Y)))))) { + // Can fold trunc nsw + zext/sext for all predicates. + YIsSExt = isa(Cmp.getOperand(0)) || + isa(Cmp.getOperand(1)); + } else return nullptr; Type *TruncTy = Cmp.getOperand(0)->getType(); @@ -1518,19 +1535,7 @@ InstCombinerImpl::foldICmpTruncWithTruncOrExt(ICmpInst &Cmp, !isDesirableIntType(X->getType()->getScalarSizeInBits())) return nullptr; - // Check if the trunc is unneeded. - KnownBits KnownX = llvm::computeKnownBits(X, /*Depth*/ 0, Q); - if (KnownX.countMaxActiveBits() > TruncBits) - return nullptr; - - if (!YIsZext) { - // If Y is also a trunc, make sure it is unneeded. - KnownBits KnownY = llvm::computeKnownBits(Y, /*Depth*/ 0, Q); - if (KnownY.countMaxActiveBits() > TruncBits) - return nullptr; - } - - Value *NewY = Builder.CreateZExtOrTrunc(Y, X->getType()); + Value *NewY = Builder.CreateIntCast(Y, X->getType(), YIsSExt); return new ICmpInst(Pred, X, NewY); } diff --git a/llvm/test/Transforms/InstCombine/icmp-of-trunc-ext.ll b/llvm/test/Transforms/InstCombine/icmp-of-trunc-ext.ll index a61694919ab040..0a8bf013dc55d2 100644 --- a/llvm/test/Transforms/InstCombine/icmp-of-trunc-ext.ll +++ b/llvm/test/Transforms/InstCombine/icmp-of-trunc-ext.ll @@ -271,9 +271,7 @@ define i1 @icmp_trunc_x_zext_y_fail_multiuse(i32 %x, i8 %y) { define i1 @trunc_unsigned_nuw(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_unsigned_nuw( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nuw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp ult i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp ult i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw i16 %x to i8 @@ -284,9 +282,7 @@ define i1 @trunc_unsigned_nuw(i16 %x, i16 %y) { define i1 @trunc_unsigned_nsw(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_unsigned_nsw( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nsw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp ult i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp ult i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i16 %x to i8 @@ -297,9 +293,7 @@ define i1 @trunc_unsigned_nsw(i16 %x, i16 %y) { define i1 @trunc_unsigned_both(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_unsigned_both( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw nsw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nuw nsw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp ult i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp ult i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw nsw i16 %x to i8 @@ -336,9 +330,7 @@ define i1 @trunc_signed_nuw(i16 %x, i16 %y) { define i1 @trunc_signed_nsw(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_signed_nsw( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nsw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp slt i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp slt i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i16 %x to i8 @@ -349,9 +341,7 @@ define i1 @trunc_signed_nsw(i16 %x, i16 %y) { define i1 @trunc_signed_both(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_signed_both( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw nsw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nuw nsw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp slt i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp slt i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw nsw i16 %x to i8 @@ -375,9 +365,7 @@ define i1 @trunc_signed_either(i16 %x, i16 %y) { define i1 @trunc_equality_nuw(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_equality_nuw( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nuw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp eq i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw i16 %x to i8 @@ -388,9 +376,7 @@ define i1 @trunc_equality_nuw(i16 %x, i16 %y) { define i1 @trunc_equality_nsw(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_equality_nsw( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nsw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp eq i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i16 %x to i8 @@ -401,9 +387,7 @@ define i1 @trunc_equality_nsw(i16 %x, i16 %y) { define i1 @trunc_equality_both(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_equality_both( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw nsw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nuw nsw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp eq i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw nsw i16 %x to i8 @@ -427,9 +411,8 @@ define i1 @trunc_equality_either(i16 %x, i16 %y) { define i1 @trunc_unsigned_nuw_zext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_unsigned_nuw_zext( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = zext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ult i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = zext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ugt i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw i32 %x to i16 @@ -453,9 +436,8 @@ define i1 @trunc_unsigned_nuw_sext(i32 %x, i8 %y) { define i1 @trunc_unsigned_nsw_zext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_unsigned_nsw_zext( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = zext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ult i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = zext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ugt i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i32 %x to i16 @@ -466,9 +448,8 @@ define i1 @trunc_unsigned_nsw_zext(i32 %x, i8 %y) { define i1 @trunc_unsigned_nsw_sext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_unsigned_nsw_sext( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = sext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ult i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = sext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ugt i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i32 %x to i16 @@ -479,9 +460,8 @@ define i1 @trunc_unsigned_nsw_sext(i32 %x, i8 %y) { define i1 @trunc_signed_nsw_sext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_signed_nsw_sext( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = sext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp slt i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = sext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp sgt i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i32 %x to i16 @@ -492,9 +472,8 @@ define i1 @trunc_signed_nsw_sext(i32 %x, i8 %y) { define i1 @trunc_signed_nsw_zext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_signed_nsw_zext( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = zext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp slt i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = zext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp sgt i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i32 %x to i16 @@ -531,9 +510,8 @@ define i1 @trunc_signed_nuw_zext(i32 %x, i8 %y) { define i1 @trunc_equality_nuw_zext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_equality_nuw_zext( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = zext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ne i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = zext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ne i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw i32 %x to i16 @@ -557,9 +535,8 @@ define i1 @trunc_equality_nuw_sext(i32 %x, i8 %y) { define i1 @trunc_equality_nsw_zext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_equality_nsw_zext( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = zext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ne i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = zext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ne i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i32 %x to i16 @@ -570,9 +547,8 @@ define i1 @trunc_equality_nsw_zext(i32 %x, i8 %y) { define i1 @trunc_equality_nsw_sext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_equality_nsw_sext( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = sext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ne i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = sext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ne i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i32 %x to i16 @@ -583,9 +559,8 @@ define i1 @trunc_equality_nsw_sext(i32 %x, i8 %y) { define i1 @trunc_equality_both_sext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_equality_both_sext( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = sext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ne i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = sext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ne i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw nsw i32 %x to i16 ``````````
llvmbot commented 2 weeks ago

@llvm/pr-subscribers-llvm-transforms

Author: Nikita Popov (nikic)

Changes Convert the existing foldICmpTruncWithTruncOrExt() fold to work with trunc nowrap flags instead of computeKnownBits(). This also allows us to generalize the fold to work with signed comparisons. Interestingly, apart from the obvious combinations like signed predicates with trunc nsw, some non-obvious ones are also legal. For example for unsigned predicates we can do the transform for two trunc nsw as well (rather than only trunc nuw). Proofs: https://alive2.llvm.org/ce/z/ndewwK --- Full diff: https://github.com/llvm/llvm-project/pull/90436.diff 3 Files Affected: - (modified) llvm/include/llvm/IR/PatternMatch.h (+27) - (modified) llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp (+30-25) - (modified) llvm/test/Transforms/InstCombine/icmp-of-trunc-ext.ll (+26-51) ``````````diff diff --git a/llvm/include/llvm/IR/PatternMatch.h b/llvm/include/llvm/IR/PatternMatch.h index 0b13b4aad9c326..f063e6531dda4f 100644 --- a/llvm/include/llvm/IR/PatternMatch.h +++ b/llvm/include/llvm/IR/PatternMatch.h @@ -1839,6 +1839,19 @@ template struct NNegZExt_match { } }; +template struct NoWrapTrunc_match { + Op_t Op; + + NoWrapTrunc_match(const Op_t &OpMatch) : Op(OpMatch) {} + + template bool match(OpTy *V) { + if (auto *I = dyn_cast(V)) + return (I->getNoWrapKind() & WrapFlags) == WrapFlags && + Op.match(I->getOperand(0)); + return false; + } +}; + /// Matches BitCast. template inline CastOperator_match @@ -1900,6 +1913,20 @@ inline CastOperator_match m_Trunc(const OpTy &Op) { return CastOperator_match(Op); } +/// Matches trunc nuw. +template +inline NoWrapTrunc_match +m_NUWTrunc(const OpTy &Op) { + return NoWrapTrunc_match(Op); +} + +/// Matches trunc nsw. +template +inline NoWrapTrunc_match +m_NSWTrunc(const OpTy &Op) { + return NoWrapTrunc_match(Op); +} + template inline match_combine_or, OpTy> m_TruncOrSelf(const OpTy &Op) { diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index 1064340cb53661..317b3aef40a97c 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -1479,19 +1479,29 @@ Instruction *InstCombinerImpl::foldICmpTruncConstant(ICmpInst &Cmp, return nullptr; } -/// Fold icmp (trunc X), (trunc Y). -/// Fold icmp (trunc X), (zext Y). +/// Fold icmp (trunc nuw/nsw X), (trunc nuw/nsw Y). +/// Fold icmp (trunc nuw/nsw X), (zext/sext Y). Instruction * InstCombinerImpl::foldICmpTruncWithTruncOrExt(ICmpInst &Cmp, const SimplifyQuery &Q) { - if (Cmp.isSigned()) - return nullptr; - Value *X, *Y; ICmpInst::Predicate Pred; - bool YIsZext = false; + bool YIsSExt = false; // Try to match icmp (trunc X), (trunc Y) if (match(&Cmp, m_ICmp(Pred, m_Trunc(m_Value(X)), m_Trunc(m_Value(Y))))) { + unsigned NoWrapFlags = cast(Cmp.getOperand(0))->getNoWrapKind() & + cast(Cmp.getOperand(1))->getNoWrapKind(); + if (Cmp.isSigned()) { + // For signed comparisons, both truncs must be nsw. + if (!(NoWrapFlags & TruncInst::NoSignedWrap)) + return nullptr; + } else { + // For unsigned and equality comparisons, either both must be nuw or + // both must be nsw, we don't care which. + if (!NoWrapFlags) + return nullptr; + } + if (X->getType() != Y->getType() && (!Cmp.getOperand(0)->hasOneUse() || !Cmp.getOperand(1)->hasOneUse())) return nullptr; @@ -1501,12 +1511,19 @@ InstCombinerImpl::foldICmpTruncWithTruncOrExt(ICmpInst &Cmp, Pred = Cmp.getSwappedPredicate(Pred); } } - // Try to match icmp (trunc X), (zext Y) - else if (match(&Cmp, m_c_ICmp(Pred, m_Trunc(m_Value(X)), - m_OneUse(m_ZExt(m_Value(Y)))))) - - YIsZext = true; - else + // Try to match icmp (trunc nuw X), (zext Y) + else if (!Cmp.isSigned() && + match(&Cmp, m_c_ICmp(Pred, m_NUWTrunc(m_Value(X)), + m_OneUse(m_ZExt(m_Value(Y)))))) { + // Can fold trunc nuw + zext for unsigned and equality predicates. + } + // Try to match icmp (trunc nsw X), (sext Y) + else if (match(&Cmp, m_c_ICmp(Pred, m_NSWTrunc(m_Value(X)), + m_OneUse(m_ZExtOrSExt(m_Value(Y)))))) { + // Can fold trunc nsw + zext/sext for all predicates. + YIsSExt = isa(Cmp.getOperand(0)) || + isa(Cmp.getOperand(1)); + } else return nullptr; Type *TruncTy = Cmp.getOperand(0)->getType(); @@ -1518,19 +1535,7 @@ InstCombinerImpl::foldICmpTruncWithTruncOrExt(ICmpInst &Cmp, !isDesirableIntType(X->getType()->getScalarSizeInBits())) return nullptr; - // Check if the trunc is unneeded. - KnownBits KnownX = llvm::computeKnownBits(X, /*Depth*/ 0, Q); - if (KnownX.countMaxActiveBits() > TruncBits) - return nullptr; - - if (!YIsZext) { - // If Y is also a trunc, make sure it is unneeded. - KnownBits KnownY = llvm::computeKnownBits(Y, /*Depth*/ 0, Q); - if (KnownY.countMaxActiveBits() > TruncBits) - return nullptr; - } - - Value *NewY = Builder.CreateZExtOrTrunc(Y, X->getType()); + Value *NewY = Builder.CreateIntCast(Y, X->getType(), YIsSExt); return new ICmpInst(Pred, X, NewY); } diff --git a/llvm/test/Transforms/InstCombine/icmp-of-trunc-ext.ll b/llvm/test/Transforms/InstCombine/icmp-of-trunc-ext.ll index a61694919ab040..0a8bf013dc55d2 100644 --- a/llvm/test/Transforms/InstCombine/icmp-of-trunc-ext.ll +++ b/llvm/test/Transforms/InstCombine/icmp-of-trunc-ext.ll @@ -271,9 +271,7 @@ define i1 @icmp_trunc_x_zext_y_fail_multiuse(i32 %x, i8 %y) { define i1 @trunc_unsigned_nuw(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_unsigned_nuw( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nuw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp ult i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp ult i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw i16 %x to i8 @@ -284,9 +282,7 @@ define i1 @trunc_unsigned_nuw(i16 %x, i16 %y) { define i1 @trunc_unsigned_nsw(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_unsigned_nsw( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nsw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp ult i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp ult i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i16 %x to i8 @@ -297,9 +293,7 @@ define i1 @trunc_unsigned_nsw(i16 %x, i16 %y) { define i1 @trunc_unsigned_both(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_unsigned_both( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw nsw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nuw nsw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp ult i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp ult i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw nsw i16 %x to i8 @@ -336,9 +330,7 @@ define i1 @trunc_signed_nuw(i16 %x, i16 %y) { define i1 @trunc_signed_nsw(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_signed_nsw( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nsw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp slt i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp slt i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i16 %x to i8 @@ -349,9 +341,7 @@ define i1 @trunc_signed_nsw(i16 %x, i16 %y) { define i1 @trunc_signed_both(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_signed_both( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw nsw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nuw nsw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp slt i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp slt i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw nsw i16 %x to i8 @@ -375,9 +365,7 @@ define i1 @trunc_signed_either(i16 %x, i16 %y) { define i1 @trunc_equality_nuw(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_equality_nuw( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nuw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp eq i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw i16 %x to i8 @@ -388,9 +376,7 @@ define i1 @trunc_equality_nuw(i16 %x, i16 %y) { define i1 @trunc_equality_nsw(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_equality_nsw( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nsw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp eq i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i16 %x to i8 @@ -401,9 +387,7 @@ define i1 @trunc_equality_nsw(i16 %x, i16 %y) { define i1 @trunc_equality_both(i16 %x, i16 %y) { ; CHECK-LABEL: @trunc_equality_both( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw nsw i16 [[X:%.*]] to i8 -; CHECK-NEXT: [[YT:%.*]] = trunc nuw nsw i16 [[Y:%.*]] to i8 -; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[XT]], [[YT]] +; CHECK-NEXT: [[C:%.*]] = icmp eq i16 [[X:%.*]], [[Y:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw nsw i16 %x to i8 @@ -427,9 +411,8 @@ define i1 @trunc_equality_either(i16 %x, i16 %y) { define i1 @trunc_unsigned_nuw_zext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_unsigned_nuw_zext( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = zext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ult i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = zext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ugt i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw i32 %x to i16 @@ -453,9 +436,8 @@ define i1 @trunc_unsigned_nuw_sext(i32 %x, i8 %y) { define i1 @trunc_unsigned_nsw_zext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_unsigned_nsw_zext( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = zext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ult i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = zext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ugt i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i32 %x to i16 @@ -466,9 +448,8 @@ define i1 @trunc_unsigned_nsw_zext(i32 %x, i8 %y) { define i1 @trunc_unsigned_nsw_sext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_unsigned_nsw_sext( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = sext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ult i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = sext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ugt i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i32 %x to i16 @@ -479,9 +460,8 @@ define i1 @trunc_unsigned_nsw_sext(i32 %x, i8 %y) { define i1 @trunc_signed_nsw_sext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_signed_nsw_sext( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = sext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp slt i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = sext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp sgt i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i32 %x to i16 @@ -492,9 +472,8 @@ define i1 @trunc_signed_nsw_sext(i32 %x, i8 %y) { define i1 @trunc_signed_nsw_zext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_signed_nsw_zext( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = zext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp slt i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = zext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp sgt i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i32 %x to i16 @@ -531,9 +510,8 @@ define i1 @trunc_signed_nuw_zext(i32 %x, i8 %y) { define i1 @trunc_equality_nuw_zext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_equality_nuw_zext( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = zext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ne i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = zext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ne i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw i32 %x to i16 @@ -557,9 +535,8 @@ define i1 @trunc_equality_nuw_sext(i32 %x, i8 %y) { define i1 @trunc_equality_nsw_zext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_equality_nsw_zext( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = zext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ne i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = zext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ne i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i32 %x to i16 @@ -570,9 +547,8 @@ define i1 @trunc_equality_nsw_zext(i32 %x, i8 %y) { define i1 @trunc_equality_nsw_sext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_equality_nsw_sext( -; CHECK-NEXT: [[XT:%.*]] = trunc nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = sext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ne i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = sext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ne i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nsw i32 %x to i16 @@ -583,9 +559,8 @@ define i1 @trunc_equality_nsw_sext(i32 %x, i8 %y) { define i1 @trunc_equality_both_sext(i32 %x, i8 %y) { ; CHECK-LABEL: @trunc_equality_both_sext( -; CHECK-NEXT: [[XT:%.*]] = trunc nuw nsw i32 [[X:%.*]] to i16 -; CHECK-NEXT: [[YE:%.*]] = sext i8 [[Y:%.*]] to i16 -; CHECK-NEXT: [[C:%.*]] = icmp ne i16 [[XT]], [[YE]] +; CHECK-NEXT: [[TMP1:%.*]] = sext i8 [[Y:%.*]] to i32 +; CHECK-NEXT: [[C:%.*]] = icmp ne i32 [[TMP1]], [[X:%.*]] ; CHECK-NEXT: ret i1 [[C]] ; %xt = trunc nuw nsw i32 %x to i16 ``````````
github-actions[bot] commented 2 weeks ago

:white_check_mark: With the latest revision this PR passed the C/C++ code formatter.

dtcxzyw commented 2 weeks ago

instead of computeKnownBits().

Does it improve the compile-time?

nikic commented 2 weeks ago

instead of computeKnownBits().

Does it improve the compile-time?

I don't see any significant compile-time change: https://llvm-compile-time-tracker.com/compare.php?from=e1622e189e8c0ef457bfac528f90a7a930d9aad2&to=b48d51be8e5956645d323123550638ba911eef69&stat=instructions:u

dtcxzyw commented 2 weeks ago

We should handle icmp pred (trunc nsw/nuw X), C first to avoid regression https://github.com/dtcxzyw/llvm-opt-benchmark/pull/567/files#r1583426017.

nikic commented 2 weeks ago

We should handle icmp pred (trunc nsw/nuw X), C first to avoid regression https://github.com/dtcxzyw/llvm-opt-benchmark/pull/567/files#r1583426017.

There is a PR for that one already here: https://github.com/llvm/llvm-project/pull/87935