Author: Nikita Popov Date: 2020-08-31T16:09:42+02:00 New Revision: 2526d8c43499fc5dd6135556ab16ae20d280ddca
URL: https://github.com/llvm/llvm-project/commit/2526d8c43499fc5dd6135556ab16ae20d280ddca DIFF: https://github.com/llvm/llvm-project/commit/2526d8c43499fc5dd6135556ab16ae20d280ddca.diff LOG: [InstSimplify] Protect against more poison in SimplifyWithOpReplaced (PR47322) Replace the check for poison-producing instructions in SimplifyWithOpReplaced() with the generic helper canCreatePoison() that properly handles poisonous shifts and thus avoids the problem from PR47322. This additionally fixes a bug in IIQ.UseInstrInfo=false mode, which previously could have caused this code to ignore poison flags. Setting UseInstrInfo=false should reduce the possible optimizations, not increase them. This is not a full solution to the problem, as poison could be introduced more indirectly. This is just a minimal, easy to backport fix. Differential Revision: https://reviews.llvm.org/D86834 (cherry picked from commit a5be86fde5de2c253aa19704bf4e4854f1936f8c) Added: Modified: llvm/lib/Analysis/InstructionSimplify.cpp llvm/test/Transforms/InstSimplify/select.ll Removed: ################################################################################ diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp index d3bdf9d6aafd..9423ff9e3a66 100644 --- a/llvm/lib/Analysis/InstructionSimplify.cpp +++ b/llvm/lib/Analysis/InstructionSimplify.cpp @@ -3837,10 +3837,7 @@ static const Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp, // TODO: This is an unusual limitation because better analysis results in // worse simplification. InstCombine can do this fold more generally // by dropping the flags. Remove this fold to save compile-time? - if (isa<OverflowingBinaryOperator>(B)) - if (Q.IIQ.hasNoSignedWrap(B) || Q.IIQ.hasNoUnsignedWrap(B)) - return nullptr; - if (isa<PossiblyExactOperator>(B) && Q.IIQ.isExact(B)) + if (canCreatePoison(I)) return nullptr; if (MaxRecurse) { diff --git a/llvm/test/Transforms/InstSimplify/select.ll b/llvm/test/Transforms/InstSimplify/select.ll index b1264138a15e..05fa46ca3f49 100644 --- a/llvm/test/Transforms/InstSimplify/select.ll +++ b/llvm/test/Transforms/InstSimplify/select.ll @@ -919,3 +919,19 @@ define <2 x i32> @all_constant_true_undef_false_constexpr_vec() { %s = select i1 ptrtoint (<2 x i32> ()* @all_constant_true_undef_false_constexpr_vec to i1), <2 x i32> undef, <2 x i32><i32 -1, i32 ptrtoint (<2 x i32> ()* @all_constant_true_undef_false_constexpr_vec to i32)> ret <2 x i32> %s } + +define i32 @pr47322_more_poisonous_replacement(i32 %arg) { +; CHECK-LABEL: @pr47322_more_poisonous_replacement( +; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[ARG:%.*]], 0 +; CHECK-NEXT: [[TRAILING:%.*]] = call i32 @llvm.cttz.i32(i32 [[ARG]], i1 immarg true) +; CHECK-NEXT: [[SHIFTED:%.*]] = lshr i32 [[ARG]], [[TRAILING]] +; CHECK-NEXT: [[R1_SROA_0_1:%.*]] = select i1 [[CMP]], i32 0, i32 [[SHIFTED]] +; CHECK-NEXT: ret i32 [[R1_SROA_0_1]] +; + %cmp = icmp eq i32 %arg, 0 + %trailing = call i32 @llvm.cttz.i32(i32 %arg, i1 immarg true) + %shifted = lshr i32 %arg, %trailing + %r1.sroa.0.1 = select i1 %cmp, i32 0, i32 %shifted + ret i32 %r1.sroa.0.1 +} +declare i32 @llvm.cttz.i32(i32, i1 immarg) _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
