[llvm] 66b34bc - [RISCV] Handled the uimm9 offset while FrameIndex folding. (#149303)

[via llvm-commits]

Author: UmeshKalappa
Date: 2025-07-30T17:43:10+02:00
New Revision: 66b34bc943644c7e20f5c5c22a706a091dd9b053

URL: https://github.com/llvm/llvm-project/commit/66b34bc943644c7e20f5c5c22a706a091dd9b053
DIFF: https://github.com/llvm/llvm-project/commit/66b34bc943644c7e20f5c5c22a706a091dd9b053.diff

LOG: [RISCV] Handled the uimm9 offset while FrameIndex folding. (#149303)

Reverted the https://github.com/llvm/llvm-project/pull/148779 changes
and

- handled the uimm9 offset in eliminateFrameIndex ()
- updated the testcase.

Added: 
    

Modified: 
    llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
    llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
    llvm/test/CodeGen/RISCV/xmips-cbop.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
index 7b0fe5f4e0f23..f223fdbef4359 100644
--- a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
@@ -2942,8 +2942,8 @@ bool RISCVDAGToDAGISel::SelectAddrRegImm(SDValue Addr, SDValue &Base,
 /// Similar to SelectAddrRegImm, except that the offset is restricted to uimm9.
 bool RISCVDAGToDAGISel::SelectAddrRegImm9(SDValue Addr, SDValue &Base,
                                           SDValue &Offset) {
-  // FIXME: Support FrameIndex. Need to teach eliminateFrameIndex that only
-  // a 9-bit immediate can be folded.
+  if (SelectAddrFrameIndex(Addr, Base, Offset))
+    return true;
 
   SDLoc DL(Addr);
   MVT VT = Addr.getSimpleValueType();
@@ -2953,8 +2953,8 @@ bool RISCVDAGToDAGISel::SelectAddrRegImm9(SDValue Addr, SDValue &Base,
     if (isUInt<9>(CVal)) {
       Base = Addr.getOperand(0);
 
-      // FIXME: Support FrameIndex. Need to teach eliminateFrameIndex that only
-      // a 9-bit immediate can be folded.
+      if (auto *FIN = dyn_cast<FrameIndexSDNode>(Base))
+        Base = CurDAG->getTargetFrameIndex(FIN->getIndex(), VT);
       Offset = CurDAG->getSignedTargetConstant(CVal, DL, VT);
       return true;
     }

diff  --git a/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp b/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
index 214536d7f3a74..af7b221c4c3b6 100644
--- a/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
@@ -576,6 +576,8 @@ bool RISCVRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
     int64_t Val = Offset.getFixed();
     int64_t Lo12 = SignExtend64<12>(Val);
     unsigned Opc = MI.getOpcode();
+    auto &Subtarget = MF.getSubtarget<RISCVSubtarget>();
+
     if (Opc == RISCV::ADDI && !isInt<12>(Val)) {
       // We chose to emit the canonical immediate sequence rather than folding
       // the offset into the using add under the theory that doing so doesn't
@@ -588,6 +590,9 @@ bool RISCVRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
                (Lo12 & 0b11111) != 0) {
       // Prefetch instructions require the offset to be 32 byte aligned.
       MI.getOperand(FIOperandNum + 1).ChangeToImmediate(0);
+    } else if (Opc == RISCV::MIPS_PREFETCH && !isUInt<9>(Val)) {
+      // MIPS Prefetch instructions require the offset to be 9 bits encoded.
+      MI.getOperand(FIOperandNum + 1).ChangeToImmediate(0);
     } else if ((Opc == RISCV::PseudoRV32ZdinxLD ||
                 Opc == RISCV::PseudoRV32ZdinxSD) &&
                Lo12 >= 2044) {

diff  --git a/llvm/test/CodeGen/RISCV/xmips-cbop.ll b/llvm/test/CodeGen/RISCV/xmips-cbop.ll
index cbbd1de13192c..0d5defc833763 100644
--- a/llvm/test/CodeGen/RISCV/xmips-cbop.ll
+++ b/llvm/test/CodeGen/RISCV/xmips-cbop.ll
@@ -1,7 +1,7 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
-; RUN: llc -mtriple=riscv32 -mattr=+xmipscbop -mattr=+m -verify-machineinstrs < %s \
+; RUN: llc -mtriple=riscv32 -mattr=+xmipscbop  -verify-machineinstrs < %s \
 ; RUN:   | FileCheck %s -check-prefix=RV32XMIPSPREFETCH
-; RUN: llc -mtriple=riscv64 -mattr=+xmipscbop -mattr=+m -verify-machineinstrs < %s \
+; RUN: llc -mtriple=riscv64 -mattr=+xmipscbop  -verify-machineinstrs < %s \
 ; RUN:   | FileCheck %s -check-prefix=RV64XMIPSPREFETCH
 
 define void @prefetch_data_read(ptr noundef %ptr) nounwind {
@@ -49,3 +49,54 @@ define void @prefetch_inst_read(ptr noundef %ptr) nounwind  {
   tail call void @llvm.prefetch.p0(ptr nonnull %arrayidx, i32 0, i32 0, i32 0)
   ret void
 }
+
+define void @prefetch_frameindex_test_neg() nounwind {
+; RV32XMIPSPREFETCH-LABEL: prefetch_frameindex_test_neg:
+; RV32XMIPSPREFETCH:       # %bb.0:
+; RV32XMIPSPREFETCH-NEXT:    lui a0, 1
+; RV32XMIPSPREFETCH-NEXT:    addi a0, a0, 16
+; RV32XMIPSPREFETCH-NEXT:    sub sp, sp, a0
+; RV32XMIPSPREFETCH-NEXT:    addi a0, sp, 524
+; RV32XMIPSPREFETCH-NEXT:    mips.pref 8, 0(a0)
+; RV32XMIPSPREFETCH-NEXT:    lui a0, 1
+; RV32XMIPSPREFETCH-NEXT:    addi a0, a0, 16
+; RV32XMIPSPREFETCH-NEXT:    add sp, sp, a0
+; RV32XMIPSPREFETCH-NEXT:    ret
+;
+; RV64XMIPSPREFETCH-LABEL: prefetch_frameindex_test_neg:
+; RV64XMIPSPREFETCH:       # %bb.0:
+; RV64XMIPSPREFETCH-NEXT:    lui a0, 1
+; RV64XMIPSPREFETCH-NEXT:    addi a0, a0, 16
+; RV64XMIPSPREFETCH-NEXT:    sub sp, sp, a0
+; RV64XMIPSPREFETCH-NEXT:    addi a0, sp, 524
+; RV64XMIPSPREFETCH-NEXT:    mips.pref 8, 0(a0)
+; RV64XMIPSPREFETCH-NEXT:    lui a0, 1
+; RV64XMIPSPREFETCH-NEXT:    addi a0, a0, 16
+; RV64XMIPSPREFETCH-NEXT:    add sp, sp, a0
+; RV64XMIPSPREFETCH-NEXT:    ret
+  %data = alloca [1024 x i32], align 4
+  %ptr = getelementptr [1024 x i32], ptr %data, i32 0, i32 127
+  call void @llvm.prefetch(ptr %ptr, i32 0, i32 0, i32 1)
+  ret void
+}
+
+define void @prefetch_frameindex_test() nounwind {
+; RV32XMIPSPREFETCH-LABEL: prefetch_frameindex_test:
+; RV32XMIPSPREFETCH:       # %bb.0:
+; RV32XMIPSPREFETCH-NEXT:    addi sp, sp, -512
+; RV32XMIPSPREFETCH-NEXT:    mips.pref 8, 32(sp)
+; RV32XMIPSPREFETCH-NEXT:    addi sp, sp, 512
+; RV32XMIPSPREFETCH-NEXT:    ret
+;
+; RV64XMIPSPREFETCH-LABEL: prefetch_frameindex_test:
+; RV64XMIPSPREFETCH:       # %bb.0:
+; RV64XMIPSPREFETCH-NEXT:    addi sp, sp, -512
+; RV64XMIPSPREFETCH-NEXT:    mips.pref 8, 32(sp)
+; RV64XMIPSPREFETCH-NEXT:    addi sp, sp, 512
+; RV64XMIPSPREFETCH-NEXT:    ret
+  %data = alloca [128 x i32], align 4
+  %base = bitcast ptr %data to ptr
+  %ptr = getelementptr [128 x i32], ptr %base, i32 0, i32 8
+  call void @llvm.prefetch(ptr %ptr, i32 0, i32 0, i32 1)
+  ret void
+}