[RISCV] Don't fold offsets into auipc if offset is larger than the reference global variable.

The global variable should be within 2GB of the PC, but an offset
to an address outside the global might not be.

Fixes #134525.

Author: topperc

llvm/lib/Target/RISCV/RISCVMergeBaseOffset.cpp

@@ -35,7 +35,7 @@ class RISCVMergeBaseOffsetOpt : public MachineFunctionPass {
   bool detectFoldable(MachineInstr &Hi, MachineInstr *&Lo);
 
   bool detectAndFoldOffset(MachineInstr &Hi, MachineInstr &Lo);
-  void foldOffset(MachineInstr &Hi, MachineInstr &Lo, MachineInstr &Tail,
+  bool foldOffset(MachineInstr &Hi, MachineInstr &Lo, MachineInstr &Tail,
                   int64_t Offset);
   bool foldLargeOffset(MachineInstr &Hi, MachineInstr &Lo,
                        MachineInstr &TailAdd, Register GSReg);
@@ -142,9 +142,21 @@ bool RISCVMergeBaseOffsetOpt::detectFoldable(MachineInstr &Hi,
 // Update the offset in Hi and Lo instructions.
 // Delete the tail instruction and update all the uses to use the
 // output from Lo.
-void RISCVMergeBaseOffsetOpt::foldOffset(MachineInstr &Hi, MachineInstr &Lo,
+bool RISCVMergeBaseOffsetOpt::foldOffset(MachineInstr &Hi, MachineInstr &Lo,
                                          MachineInstr &Tail, int64_t Offset) {
   assert(isInt<32>(Offset) && "Unexpected offset");
+
+  // If Hi is an AUIPC, don't fold the offset if it is outside the bounds of
+  // the global object. The object may be within 2GB of the PC, but addresses
+  // outside of the object might not be.
+  if (Hi.getOpcode() == RISCV::AUIPC && Hi.getOperand(1).isGlobal()) {
+    const GlobalValue *GV = Hi.getOperand(1).getGlobal();
+    Type *Ty = GV->getValueType();
+    if (!Ty->isSized() || Offset < 0 ||
+        (uint64_t)Offset > GV->getDataLayout().getTypeAllocSize(Ty))
+      return false;
+  }
+
   // Put the offset back in Hi and the Lo
   Hi.getOperand(1).setOffset(Offset);
   if (Hi.getOpcode() != RISCV::AUIPC)
@@ -156,6 +168,7 @@ void RISCVMergeBaseOffsetOpt::foldOffset(MachineInstr &Hi, MachineInstr &Lo,
   Tail.eraseFromParent();
   LLVM_DEBUG(dbgs() << "  Merged offset " << Offset << " into base.\n"
                     << "     " << Hi << "     " << Lo;);
+  return true;
 }
 
 // Detect patterns for large offsets that are passed into an ADD instruction.
@@ -205,7 +218,8 @@ bool RISCVMergeBaseOffsetOpt::foldLargeOffset(MachineInstr &Hi,
     // Handle rs1 of ADDI is X0.
     if (AddiReg == RISCV::X0) {
       LLVM_DEBUG(dbgs() << "  Offset Instrs: " << OffsetTail);
-      foldOffset(Hi, Lo, TailAdd, OffLo);
+      if (!foldOffset(Hi, Lo, TailAdd, OffLo))
+        return false;
       OffsetTail.eraseFromParent();
       return true;
     }
@@ -226,7 +240,8 @@ bool RISCVMergeBaseOffsetOpt::foldLargeOffset(MachineInstr &Hi,
       return false;
     LLVM_DEBUG(dbgs() << "  Offset Instrs: " << OffsetTail
                       << "                 " << OffsetLui);
-    foldOffset(Hi, Lo, TailAdd, Offset);
+    if (!foldOffset(Hi, Lo, TailAdd, Offset))
+      return false;
     OffsetTail.eraseFromParent();
     OffsetLui.eraseFromParent();
     return true;
@@ -235,7 +250,8 @@ bool RISCVMergeBaseOffsetOpt::foldLargeOffset(MachineInstr &Hi,
     // exists.
     LLVM_DEBUG(dbgs() << "  Offset Instr: " << OffsetTail);
     int64_t Offset = SignExtend64<32>(OffsetTail.getOperand(1).getImm() << 12);
-    foldOffset(Hi, Lo, TailAdd, Offset);
+    if (!foldOffset(Hi, Lo, TailAdd, Offset))
+      return false;
     OffsetTail.eraseFromParent();
     return true;
   }
@@ -294,7 +310,8 @@ bool RISCVMergeBaseOffsetOpt::foldShiftedOffset(MachineInstr &Hi,
   Offset = (uint64_t)Offset << ShAmt;
 
   LLVM_DEBUG(dbgs() << "  Offset Instr: " << OffsetTail);
-  foldOffset(Hi, Lo, TailShXAdd, Offset);
+  if (!foldOffset(Hi, Lo, TailShXAdd, Offset))
+    return false;
   OffsetTail.eraseFromParent();
   return true;
 }
@@ -327,15 +344,15 @@ bool RISCVMergeBaseOffsetOpt::detectAndFoldOffset(MachineInstr &Hi,
       if (TailTail.getOpcode() == RISCV::ADDI) {
         Offset += TailTail.getOperand(2).getImm();
         LLVM_DEBUG(dbgs() << "  Offset Instrs: " << Tail << TailTail);
-        foldOffset(Hi, Lo, TailTail, Offset);
+        if (!foldOffset(Hi, Lo, TailTail, Offset))
+          return false;
         Tail.eraseFromParent();
         return true;
       }
     }
 
     LLVM_DEBUG(dbgs() << "  Offset Instr: " << Tail);
-    foldOffset(Hi, Lo, Tail, Offset);
-    return true;
+    return foldOffset(Hi, Lo, Tail, Offset);
   }
   case RISCV::ADD:
     // The offset is too large to fit in the immediate field of ADDI.

llvm/test/CodeGen/RISCV/fold-addi-loadstore.ll

@@ -1227,3 +1227,72 @@ for.inc.peel:                                     ; preds = %entry
   store i32 %spec.select, ptr null, align 4
   ret i32 0
 }
+
+@ki_end = external dso_local global [0 x i8], align 1
+
+define i1 @pr134525() nounwind {
+; RV32I-LABEL: pr134525:
+; RV32I:       # %bb.0: # %entry
+; RV32I-NEXT:    lui a0, %hi(ki_end)
+; RV32I-NEXT:    addi a0, a0, %lo(ki_end)
+; RV32I-NEXT:    lui a1, 523776
+; RV32I-NEXT:    lui a2, 32
+; RV32I-NEXT:    add a1, a0, a1
+; RV32I-NEXT:    addi a2, a2, 1
+; RV32I-NEXT:    sltu a2, a1, a2
+; RV32I-NEXT:    sltu a0, a1, a0
+; RV32I-NEXT:    not a0, a0
+; RV32I-NEXT:    and a0, a0, a2
+; RV32I-NEXT:    ret
+;
+; RV32I-MEDIUM-LABEL: pr134525:
+; RV32I-MEDIUM:       # %bb.0: # %entry
+; RV32I-MEDIUM-NEXT:  .Lpcrel_hi15:
+; RV32I-MEDIUM-NEXT:    auipc a0, %pcrel_hi(ki_end)
+; RV32I-MEDIUM-NEXT:    lui a1, 523776
+; RV32I-MEDIUM-NEXT:    lui a2, 32
+; RV32I-MEDIUM-NEXT:    addi a0, a0, %pcrel_lo(.Lpcrel_hi15)
+; RV32I-MEDIUM-NEXT:    addi a2, a2, 1
+; RV32I-MEDIUM-NEXT:    add a1, a0, a1
+; RV32I-MEDIUM-NEXT:    sltu a2, a1, a2
+; RV32I-MEDIUM-NEXT:    sltu a0, a1, a0
+; RV32I-MEDIUM-NEXT:    not a0, a0
+; RV32I-MEDIUM-NEXT:    and a0, a0, a2
+; RV32I-MEDIUM-NEXT:    ret
+;
+; RV64I-LABEL: pr134525:
+; RV64I:       # %bb.0: # %entry
+; RV64I-NEXT:    lui a0, %hi(ki_end+2145386496)
+; RV64I-NEXT:    addi a0, a0, %lo(ki_end+2145386496)
+; RV64I-NEXT:    lui a1, 32
+; RV64I-NEXT:    addiw a1, a1, 1
+; RV64I-NEXT:    sltu a0, a0, a1
+; RV64I-NEXT:    ret
+;
+; RV64I-MEDIUM-LABEL: pr134525:
+; RV64I-MEDIUM:       # %bb.0: # %entry
+; RV64I-MEDIUM-NEXT:  .Lpcrel_hi15:
+; RV64I-MEDIUM-NEXT:    auipc a0, %pcrel_hi(ki_end)
+; RV64I-MEDIUM-NEXT:    lui a1, 523776
+; RV64I-MEDIUM-NEXT:    addi a0, a0, %pcrel_lo(.Lpcrel_hi15)
+; RV64I-MEDIUM-NEXT:    add a0, a0, a1
+; RV64I-MEDIUM-NEXT:    lui a1, 32
+; RV64I-MEDIUM-NEXT:    addiw a1, a1, 1
+; RV64I-MEDIUM-NEXT:    sltu a0, a0, a1
+; RV64I-MEDIUM-NEXT:    ret
+;
+; RV64I-LARGE-LABEL: pr134525:
+; RV64I-LARGE:       # %bb.0: # %entry
+; RV64I-LARGE-NEXT:  .Lpcrel_hi16:
+; RV64I-LARGE-NEXT:    auipc a0, %pcrel_hi(.LCPI22_0)
+; RV64I-LARGE-NEXT:    ld a0, %pcrel_lo(.Lpcrel_hi16)(a0)
+; RV64I-LARGE-NEXT:    lui a1, 523776
+; RV64I-LARGE-NEXT:    add a0, a0, a1
+; RV64I-LARGE-NEXT:    lui a1, 32
+; RV64I-LARGE-NEXT:    addiw a1, a1, 1
+; RV64I-LARGE-NEXT:    sltu a0, a0, a1
+; RV64I-LARGE-NEXT:    ret
+entry:
+  %cmp = icmp ult i64 sub (i64 ptrtoint (ptr @ki_end to i64), i64 -2145386496), 131073
+  ret i1 %cmp
+}