diff options
| -rw-r--r-- | lib/Transforms/Scalar/MemCpyOptimizer.cpp | 17 | ||||
| -rw-r--r-- | test/Transforms/MemCpyOpt/memcpy.ll | 9 |
2 files changed, 22 insertions, 4 deletions
diff --git a/lib/Transforms/Scalar/MemCpyOptimizer.cpp b/lib/Transforms/Scalar/MemCpyOptimizer.cpp index 6f93e326ba..4c487e0a34 100644 --- a/lib/Transforms/Scalar/MemCpyOptimizer.cpp +++ b/lib/Transforms/Scalar/MemCpyOptimizer.cpp @@ -762,6 +762,14 @@ bool MemCpyOpt::processMemCpy(MemCpyInst *M) { ConstantInt *CopySize = dyn_cast<ConstantInt>(M->getLength()); if (CopySize == 0 || M->isVolatile()) return false; + // If the source and destination of the memcpy are the same, then zap it. + if (M->getSource() == M->getDest()) { + MD->removeInstruction(M); + M->eraseFromParent(); + return false; + } + + // The are two possible optimizations we can do for memcpy: // a) memcpy-memcpy xform which exposes redundance for DSE. // b) call-memcpy xform for return slot optimization. @@ -773,10 +781,11 @@ bool MemCpyOpt::processMemCpy(MemCpyInst *M) { return processMemCpyMemCpyDependence(M, MDep, CopySize->getZExtValue()); if (CallInst *C = dyn_cast<CallInst>(DepInfo.getInst())) { - bool changed = performCallSlotOptzn(M, M->getDest(), M->getSource(), - CopySize->getZExtValue(), C); - if (changed) M->eraseFromParent(); - return changed; + if (performCallSlotOptzn(M, M->getDest(), M->getSource(), + CopySize->getZExtValue(), C)) { + M->eraseFromParent(); + return true; + } } return false; } diff --git a/test/Transforms/MemCpyOpt/memcpy.ll b/test/Transforms/MemCpyOpt/memcpy.ll index 16b80a628a..b387d32a7d 100644 --- a/test/Transforms/MemCpyOpt/memcpy.ll +++ b/test/Transforms/MemCpyOpt/memcpy.ll @@ -100,3 +100,12 @@ entry: ; CHECK: store i8 4 ; CHECK: call void @test5a(%struct.S* byval align 16 %y) } + +;; Noop memcpy should be zapped. +define void @test6(i8 *%P) { + call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %P, i64 8, i32 4, i1 false) + ret void +; CHECK: @test6 +; CHECK-NEXT: ret void +} + |