diff options
| -rw-r--r-- | llvm/include/llvm/IR/Instruction.h | 8 | ||||
| -rw-r--r-- | llvm/lib/IR/Instruction.cpp | 5 | ||||
| -rw-r--r-- | llvm/lib/Transforms/Scalar/SCCP.cpp | 2 | ||||
| -rw-r--r-- | llvm/test/Transforms/IPConstantProp/remove-call-inst.ll | 33 | ||||
| -rw-r--r-- | llvm/test/Transforms/IPConstantProp/user-with-multiple-uses.ll | 5 |
5 files changed, 49 insertions, 4 deletions
diff --git a/llvm/include/llvm/IR/Instruction.h b/llvm/include/llvm/IR/Instruction.h index 6af9cbfae5d..76bc4010d8c 100644 --- a/llvm/include/llvm/IR/Instruction.h +++ b/llvm/include/llvm/IR/Instruction.h @@ -535,6 +535,14 @@ public: /// matters, isSafeToSpeculativelyExecute may be more appropriate. bool mayHaveSideEffects() const { return mayWriteToMemory() || mayThrow(); } + /// Return true if the instruction can be removed if the result is unused. + /// + /// When constant folding some instructions cannot be removed even if their + /// results are unused. Specifically terminator instructions and calls that + /// may have side effects cannot be removed without semantically changing the + /// generated program. + bool isSafeToRemove() const; + /// Return true if the instruction is a variety of EH-block. bool isEHPad() const { switch (getOpcode()) { diff --git a/llvm/lib/IR/Instruction.cpp b/llvm/lib/IR/Instruction.cpp index 5f2a6146ad8..215c6907256 100644 --- a/llvm/lib/IR/Instruction.cpp +++ b/llvm/lib/IR/Instruction.cpp @@ -589,6 +589,11 @@ bool Instruction::mayThrow() const { return isa<ResumeInst>(this); } +bool Instruction::isSafeToRemove() const { + return (!isa<CallInst>(this) || !this->mayHaveSideEffects()) && + !isa<TerminatorInst>(this); +} + bool Instruction::isAssociative() const { unsigned Opcode = getOpcode(); if (isAssociative(Opcode)) diff --git a/llvm/lib/Transforms/Scalar/SCCP.cpp b/llvm/lib/Transforms/Scalar/SCCP.cpp index df6053ac201..b6d034e9fb9 100644 --- a/llvm/lib/Transforms/Scalar/SCCP.cpp +++ b/llvm/lib/Transforms/Scalar/SCCP.cpp @@ -1900,7 +1900,7 @@ static bool runIPSCCP(Module &M, const DataLayout &DL, if (Inst->getType()->isVoidTy()) continue; if (tryToReplaceWithConstant(Solver, Inst)) { - if (!isa<CallInst>(Inst) && !isa<TerminatorInst>(Inst)) + if (Inst->isSafeToRemove()) Inst->eraseFromParent(); // Hey, we just changed something! MadeChanges = true; diff --git a/llvm/test/Transforms/IPConstantProp/remove-call-inst.ll b/llvm/test/Transforms/IPConstantProp/remove-call-inst.ll new file mode 100644 index 00000000000..943086ab466 --- /dev/null +++ b/llvm/test/Transforms/IPConstantProp/remove-call-inst.ll @@ -0,0 +1,33 @@ +; RUN: opt < %s -S -ipsccp | FileCheck %s +; PR5596 + +; IPSCCP should propagate the 0 argument, eliminate the switch, and propagate +; the result. + +; CHECK: define i32 @main() #0 { +; CHECK-NEXT: entry: +; CHECK-NOT: call +; CHECK-NEXT: ret i32 123 + +define i32 @main() noreturn nounwind { +entry: + %call2 = tail call i32 @wwrite(i64 0) nounwind + ret i32 %call2 +} + +define internal i32 @wwrite(i64 %i) nounwind readnone { +entry: + switch i64 %i, label %sw.default [ + i64 3, label %return + i64 10, label %return + ] + +sw.default: + ret i32 123 + +return: + ret i32 0 +} + +; CHECK: attributes #0 = { noreturn nounwind } +; CHECK: attributes #1 = { nounwind readnone } diff --git a/llvm/test/Transforms/IPConstantProp/user-with-multiple-uses.ll b/llvm/test/Transforms/IPConstantProp/user-with-multiple-uses.ll index 968718084e4..3146709aec6 100644 --- a/llvm/test/Transforms/IPConstantProp/user-with-multiple-uses.ll +++ b/llvm/test/Transforms/IPConstantProp/user-with-multiple-uses.ll @@ -15,7 +15,7 @@ entry: ret i32 %call2 } -define internal i32 @wwrite(i64 %i) nounwind readnone { +define internal i32 @wwrite(i64 %i) nounwind { entry: switch i64 %i, label %sw.default [ i64 3, label %return @@ -30,5 +30,4 @@ return: } ; CHECK: attributes #0 = { noreturn nounwind } -; CHECK: attributes #1 = { nounwind readnone } -; CHECK: attributes [[NUW]] = { nounwind } +; CHECK: attributes #1 = { nounwind } |
