From 45efcf0c9608e12f1536c855d5e9df94bb4fedb2 Mon Sep 17 00:00:00 2001 From: Reid Kleckner Date: Mon, 8 May 2017 23:20:27 +0000 Subject: Use the frame index side table for byval and inalloca arguments Summary: For inalloca functions, this is a very common code pattern: %argpack = type <{ i32, i32, i32 }> define void @f(%argpack* inalloca %args) { entry: %a = getelementptr inbounds %argpack, %argpack* %args, i32 0, i32 0 %b = getelementptr inbounds %argpack, %argpack* %args, i32 0, i32 1 %c = getelementptr inbounds %argpack, %argpack* %args, i32 0, i32 2 tail call void @llvm.dbg.declare(metadata i32* %a, ... "a") tail call void @llvm.dbg.declare(metadata i32* %c, ... "b") tail call void @llvm.dbg.declare(metadata i32* %b, ... "c") Even though these GEPs can be simplified to a constant offset from EBP or RSP, we don't do that at -O0, and each GEP is computed into a register. Registers used to compute argument addresses are typically spilled and clobbered very quickly after the initial computation, so live debug variable tracking loses information very quickly if we use DBG_VALUE instructions. This change moves processing of dbg.declare between argument lowering and basic block isel, so that we can ask if an argument has a frame index or not. If the argument lives in a register as is the case for byval arguments on some targets, then we don't put it in the side table and during ISel we emit DBG_VALUE instructions. Reviewers: aprantl Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D32980 llvm-svn: 302483 --- llvm/lib/CodeGen/SelectionDAG/FastISel.cpp | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) (limited to 'llvm/lib/CodeGen/SelectionDAG/FastISel.cpp') diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp index 8c98e3740f6..f37790d0983 100644 --- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp @@ -1150,16 +1150,16 @@ bool FastISel::selectIntrinsicCall(const IntrinsicInst *II) { return true; } - unsigned Offset = 0; + // Byval arguments with frame indices were already handled after argument + // lowering and before isel. + const auto *Arg = + dyn_cast(Address->stripInBoundsConstantOffsets()); + if (Arg && FuncInfo.getArgumentFrameIndex(Arg) != INT_MAX) + return true; + Optional Op; - if (const auto *Arg = dyn_cast(Address)) - // Some arguments' frame index is recorded during argument lowering. - Offset = FuncInfo.getArgumentFrameIndex(Arg); - if (Offset) - Op = MachineOperand::CreateFI(Offset); - if (!Op) - if (unsigned Reg = lookUpRegForValue(Address)) - Op = MachineOperand::CreateReg(Reg, false); + if (unsigned Reg = lookUpRegForValue(Address)) + Op = MachineOperand::CreateReg(Reg, false); // If we have a VLA that has a "use" in a metadata node that's then used // here but it has no other uses, then we have a problem. E.g., -- cgit v1.2.3