[RISCV] Support (addi (addi globaladdr, C1), C2) in RISCVMergeBaseOffset.

Add with immediates in the range [-4096, -2049] or [2048, 4095] get
convert to two ADDIs. Teach RISCVMergeBaseOffset to recognize this
pattern as well.

Reviewed By: luismarques

Differential Revision: https://reviews.llvm.org/D126843

diff --git a/llvm/lib/Target/RISCV/RISCVMergeBaseOffset.cpp b/llvm/lib/Target/RISCV/RISCVMergeBaseOffset.cpp
index 15f004b..6452f1a 100644 (file)
--- a/llvm/lib/Target/RISCV/RISCVMergeBaseOffset.cpp
+++ b/llvm/lib/Target/RISCV/RISCVMergeBaseOffset.cpp
@@ -207,6 +207,19 @@ bool RISCVMergeBaseOffsetOpt::detectAndFoldOffset(MachineInstr &HiLUI,
   case RISCV::ADDI: {
     // Offset is simply an immediate operand.
     int64_t Offset = Tail.getOperand(2).getImm();
+
+    // We might have two ADDIs in a row.
+    Register TailDestReg = Tail.getOperand(0).getReg();
+    if (MRI->hasOneUse(TailDestReg)) {
+      MachineInstr &TailTail = *MRI->use_instr_begin(TailDestReg);
+      if (TailTail.getOpcode() == RISCV::ADDI) {
+        Offset += TailTail.getOperand(2).getImm();
+        DeadInstrs.insert(&Tail);
+        foldOffset(HiLUI, LoADDI, TailTail, Offset);
+        return true;
+      }
+    }
+
     LLVM_DEBUG(dbgs() << "  Offset Instr: " << Tail);
     foldOffset(HiLUI, LoADDI, Tail, Offset);
     return true;

diff --git a/llvm/test/CodeGen/RISCV/hoist-global-addr-base.ll b/llvm/test/CodeGen/RISCV/hoist-global-addr-base.ll
index a0fe752..e7ede7e 100644 (file)
--- a/llvm/test/CodeGen/RISCV/hoist-global-addr-base.ll
+++ b/llvm/test/CodeGen/RISCV/hoist-global-addr-base.ll
@@ -221,3 +221,21 @@ define i8* @neg_offset_not_simm32() {
 ; RV64-NEXT:    ret
     ret i8* getelementptr inbounds ([0 x i8], [0 x i8]* @bar, i32 0, i64 -2147485013)
 }
+
+define i8* @offset_addi_addi() {
+; CHECK-LABEL: offset_addi_addi:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    lui a0, %hi(bar+3211)
+; CHECK-NEXT:    addi a0, a0, %lo(bar+3211)
+; CHECK-NEXT:    ret
+    ret i8* getelementptr inbounds ([0 x i8], [0 x i8]* @bar, i32 0, i64 3211)
+}
+
+define i8* @offset_addi_addi_neg() {
+; CHECK-LABEL: offset_addi_addi_neg:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    lui a0, %hi(bar-4000)
+; CHECK-NEXT:    addi a0, a0, %lo(bar-4000)
+; CHECK-NEXT:    ret
+    ret i8* getelementptr inbounds ([0 x i8], [0 x i8]* @bar, i32 0, i64 -4000)
+}