diff options
| -rw-r--r-- | llvm/lib/CodeGen/CodeGenPrepare.cpp | 16 | ||||
| -rw-r--r-- | llvm/test/Transforms/CodeGenPrepare/X86/sink-addrmode.ll | 35 |
2 files changed, 45 insertions, 6 deletions
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp index 3080757487e..45dc13d58de 100644 --- a/llvm/lib/CodeGen/CodeGenPrepare.cpp +++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp @@ -4278,11 +4278,17 @@ bool CodeGenPrepare::optimizeMemoryInst(Instruction *MemoryInst, Value *Addr, Value *V = worklist.back(); worklist.pop_back(); - // Break use-def graph loops. - if (!Visited.insert(V).second) { - AddrModeFound = false; - break; - } + // We allow traversing cyclic Phi nodes. + // In case of success after this loop we ensure that traversing through + // Phi nodes ends up with all cases to compute address of the form + // BaseGV + Base + Scale * Index + Offset + // where Scale and Offset are constans and BaseGV, Base and Index + // are exactly the same Values in all cases. + // It means that BaseGV, Scale and Offset dominate our memory instruction + // and have the same value as they had in address computation represented + // as Phi. So we can safely sink address computation to memory instruction. + if (!Visited.insert(V).second) + continue; // For a PHI node, push all of its incoming values. if (PHINode *P = dyn_cast<PHINode>(V)) { diff --git a/llvm/test/Transforms/CodeGenPrepare/X86/sink-addrmode.ll b/llvm/test/Transforms/CodeGenPrepare/X86/sink-addrmode.ll index b6b77579782..088b177c2e1 100644 --- a/llvm/test/Transforms/CodeGenPrepare/X86/sink-addrmode.ll +++ b/llvm/test/Transforms/CodeGenPrepare/X86/sink-addrmode.ll @@ -194,7 +194,6 @@ rare.2: br label %fallthrough } - declare void @slowpath(i32, i32*) ; Make sure we don't end up in an infinite loop after we fail to sink. @@ -218,3 +217,37 @@ load.i145: pl_loop.i.i122: br label %pl_loop.i.i122 } + +; Make sure we can sink address computation even +; if there is a cycle in phi nodes. +define void @test9(i1 %cond, i64* %base) { +; CHECK-LABEL: @test9 +entry: + %addr = getelementptr inbounds i64, i64* %base, i64 5 + %casted = bitcast i64* %addr to i32* + br label %header + +header: + %iv = phi i32 [0, %entry], [%iv.inc, %backedge] + %casted.loop = phi i32* [%casted, %entry], [%casted.merged, %backedge] + br i1 %cond, label %if.then, label %backedge + +if.then: + call void @foo(i32 %iv) + %addr.1 = getelementptr inbounds i64, i64* %base, i64 5 + %casted.1 = bitcast i64* %addr.1 to i32* + br label %backedge + +backedge: +; CHECK-LABEL: backedge: +; CHECK: getelementptr i8, {{.+}} 40 + %casted.merged = phi i32* [%casted.loop, %header], [%casted.1, %if.then] + %v = load i32, i32* %casted.merged, align 4 + call void @foo(i32 %v) + %iv.inc = add i32 %iv, 1 + %cmp = icmp slt i32 %iv.inc, 1000 + br i1 %cmp, label %header, label %exit + +exit: + ret void +} |
