From 4a3e0001e367a930cb7dec2dcd072cc512825aff Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Mon, 13 Oct 2025 11:10:41 +0200 Subject: [PATCH] [IR] Handle trunc for ptrtoaddr(inttoptr) cast pair (#162842) For ptrtoint(inttoptr) and ptrtoaddr(inttoptr), handle the case where the source and destination size do not match and convert to either zext or trunc. We can't do this if the middle size is smaller than both src/dest, because we'd have to perform an additional masking operation in that case. Most of these cases are handled by dint of ptrtoint/inttoptr size canonicalization (so I added some unit tests instead). However, the ptrtoaddr(inttoptr) case where the pointer size and address size differ is relevant, as in that case the mismatch in integer sizes is canonical. --- llvm/lib/IR/Instructions.cpp | 16 +++++--- llvm/test/Transforms/InstCombine/ptrtoaddr.ll | 5 +-- llvm/unittests/IR/InstructionsTest.cpp | 40 ++++++++++++++++++- 3 files changed, 50 insertions(+), 11 deletions(-) diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp index 88e7c44a8b88..9060a89bb15f 100644 --- a/llvm/lib/IR/Instructions.cpp +++ b/llvm/lib/IR/Instructions.cpp @@ -2965,8 +2965,7 @@ unsigned CastInst::isEliminableCastPair(Instruction::CastOps firstOp, // zext, sext -> zext, because sext can't sign extend after zext return Instruction::ZExt; case 11: { - // inttoptr, ptrtoint/ptrtoaddr -> bitcast if SrcSize<=PtrSize/AddrSize - // and SrcSize==DstSize + // inttoptr, ptrtoint/ptrtoaddr -> integer cast if (!DL) return 0; unsigned MidSize = secondOp == Instruction::PtrToAddr @@ -2974,10 +2973,15 @@ unsigned CastInst::isEliminableCastPair(Instruction::CastOps firstOp, : DL->getPointerTypeSizeInBits(MidTy); unsigned SrcSize = SrcTy->getScalarSizeInBits(); unsigned DstSize = DstTy->getScalarSizeInBits(); - // TODO: Could also produce zext or trunc here. - if (SrcSize <= MidSize && SrcSize == DstSize) - return Instruction::BitCast; - return 0; + // If the middle size is smaller than both source and destination, + // an additional masking operation would be required. + if (MidSize < SrcSize && MidSize < DstSize) + return 0; + if (DstSize < SrcSize) + return Instruction::Trunc; + if (DstSize > SrcSize) + return Instruction::ZExt; + return Instruction::BitCast; } case 12: // addrspacecast, addrspacecast -> bitcast, if SrcAS == DstAS diff --git a/llvm/test/Transforms/InstCombine/ptrtoaddr.ll b/llvm/test/Transforms/InstCombine/ptrtoaddr.ll index 7b0b15299021..ffaa8b110e32 100644 --- a/llvm/test/Transforms/InstCombine/ptrtoaddr.ll +++ b/llvm/test/Transforms/InstCombine/ptrtoaddr.ll @@ -23,10 +23,7 @@ define i64 @ptrtoaddr_inttoptr_arg(i64 %a) { define i32 @ptrtoaddr_inttoptr_arg_addrsize(i32 %a) { ; CHECK-LABEL: define i32 @ptrtoaddr_inttoptr_arg_addrsize( ; CHECK-SAME: i32 [[A:%.*]]) { -; CHECK-NEXT: [[TMP1:%.*]] = zext i32 [[A]] to i64 -; CHECK-NEXT: [[TOPTR:%.*]] = inttoptr i64 [[TMP1]] to ptr addrspace(1) -; CHECK-NEXT: [[TOADDR:%.*]] = ptrtoaddr ptr addrspace(1) [[TOPTR]] to i32 -; CHECK-NEXT: ret i32 [[TOADDR]] +; CHECK-NEXT: ret i32 [[A]] ; %toptr = inttoptr i32 %a to ptr addrspace(1) %toaddr = ptrtoaddr ptr addrspace(1) %toptr to i32 diff --git a/llvm/unittests/IR/InstructionsTest.cpp b/llvm/unittests/IR/InstructionsTest.cpp index fe9e7e822849..f4693bfb1a4d 100644 --- a/llvm/unittests/IR/InstructionsTest.cpp +++ b/llvm/unittests/IR/InstructionsTest.cpp @@ -606,12 +606,14 @@ TEST(InstructionTest, ConstrainedTrans) { TEST(InstructionsTest, isEliminableCastPair) { LLVMContext C; - DataLayout DL1("p1:32:32"); + DataLayout DL1("p1:32:32-p2:64:64:64:32"); Type *Int16Ty = Type::getInt16Ty(C); + Type *Int32Ty = Type::getInt32Ty(C); Type *Int64Ty = Type::getInt64Ty(C); Type *PtrTy64 = PointerType::get(C, 0); Type *PtrTy32 = PointerType::get(C, 1); + Type *PtrTy64_32 = PointerType::get(C, 2); // Source and destination pointers have same size -> bitcast. EXPECT_EQ(CastInst::isEliminableCastPair(CastInst::PtrToInt, @@ -637,6 +639,42 @@ TEST(InstructionsTest, isEliminableCastPair) { Int64Ty, &DL1), 0U); + // Destination larger than source. Pointer type same as destination. + EXPECT_EQ(CastInst::isEliminableCastPair(CastInst::IntToPtr, + CastInst::PtrToInt, Int16Ty, PtrTy64, + Int64Ty, &DL1), + CastInst::ZExt); + + // Destination larger than source. Pointer type different from destination. + EXPECT_EQ(CastInst::isEliminableCastPair(CastInst::IntToPtr, + CastInst::PtrToInt, Int16Ty, PtrTy32, + Int64Ty, &DL1), + CastInst::ZExt); + + // Destination smaller than source. Pointer type same as source. + EXPECT_EQ(CastInst::isEliminableCastPair(CastInst::IntToPtr, + CastInst::PtrToInt, Int64Ty, PtrTy64, + Int16Ty, &DL1), + CastInst::Trunc); + + // Destination smaller than source. Pointer type different from source. + EXPECT_EQ(CastInst::isEliminableCastPair(CastInst::IntToPtr, + CastInst::PtrToInt, Int64Ty, PtrTy32, + Int16Ty, &DL1), + CastInst::Trunc); + + // ptrtoaddr with address size != pointer size. Truncating case. + EXPECT_EQ(CastInst::isEliminableCastPair(CastInst::IntToPtr, + CastInst::PtrToAddr, Int64Ty, + PtrTy64_32, Int32Ty, &DL1), + CastInst::Trunc); + + // ptrtoaddr with address size != pointer size. Non-truncating case. + EXPECT_EQ(CastInst::isEliminableCastPair(CastInst::IntToPtr, + CastInst::PtrToAddr, Int32Ty, + PtrTy64_32, Int32Ty, &DL1), + CastInst::BitCast); + // Test that we don't eliminate bitcasts between different address spaces, // or if we don't have available pointer size information. DataLayout DL2("e-p:32:32:32-p1:16:16:16-p2:64:64:64-i1:8:8-i8:8:8-i16:16:16"