[PATCH] [LegalizeTypes][RISCV] Correctly sign-extend comparison for ATOMIC_CMP_XCHG

Summary:
Currently, the comparison argument used for ATOMIC_CMP_XCHG is legalised
with GetPromotedInteger, which leaves the upper bits of the value
undefind. Since this is used for comparing in an LR/SC loop with a
full-width comparison, we must sign extend it. We introduce a new
getExtendForAtomicCmpSwapArg to complement getExtendForAtomicOps, since
many targets have compare-and-swap instructions (or pseudos) that
correctly handle an any-extend input, and the existing function
determines the extension of the result, whereas we are concerned with
the input.

This is related to https://reviews.llvm.org/D58829, which solved the
issue for ATOMIC_CMP_SWAP_WITH_SUCCESS, but not the simpler
ATOMIC_CMP_SWAP.

Reviewers: asb, lenary, efriedma

Reviewed By: asb

Subscribers: arichardson, hiraditya, rbar, johnrusso, simoncook, sabuasal, niosHD, kito-cheng, shiva0217, MaskRay, zzheng, edward-jones, rogfer01, MartinMosbeck, brucehoult, the_o, rkruppe, jfb, PkmX, jocewei, psnobl, benna, Jim, s.egerton, pzheng, sameer.abuasal, apazos, luismarques, evandro, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74453

Gbp-Pq: Name D74453-riscv-atomic_cmp_xchg.diff

diff --git a/llvm/include/llvm/CodeGen/TargetLowering.h b/llvm/include/llvm/CodeGen/TargetLowering.h
index ca7548cd8d6f5654d61fcf2dcfe86f5305b51e56..3c9e0bd39a9cd5f951e53abede8a3919b4020e28 100644 (file)
--- a/llvm/include/llvm/CodeGen/TargetLowering.h
+++ b/llvm/include/llvm/CodeGen/TargetLowering.h
@@ -1814,6 +1814,18 @@ public:
     return ISD::ZERO_EXTEND;
   }
 
+  /// Returns how the platform's atomic compare and swap expects its comparison
+  /// value to be extended (ZERO_EXTEND, SIGN_EXTEND, or ANY_EXTEND). This is
+  /// separate from getExtendForAtomicOps, which is concerned with the
+  /// sign-extension of the instruction's output, whereas here we are concerned
+  /// with the sign-extension of the input. For targets with compare-and-swap
+  /// instructions (or sub-word comparisons in their LL/SC loop expansions),
+  /// the input can be ANY_EXTEND, but the output will still have a specific
+  /// extension.
+  virtual ISD::NodeType getExtendForAtomicCmpSwapArg() const {
+    return ISD::ANY_EXTEND;
+  }
+
   /// @}
 
   /// Returns true if we should normalize

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
index 15ac45c37c667734ee3b1d053dbc823a5cba26e9..94adcd742f903f1ffc5de370ddd968e08b4c2bb1 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
@@ -259,8 +259,24 @@ SDValue DAGTypeLegalizer::PromoteIntRes_AtomicCmpSwap(AtomicSDNode *N,
     return Res.getValue(1);
   }
 
-  SDValue Op2 = GetPromotedInteger(N->getOperand(2));
+  // Op2 is used for the comparison and thus must be extended according to the
+  // target's atomic operations. Op3 is merely stored and so can be left alone.
+  SDValue Op2 = N->getOperand(2);
   SDValue Op3 = GetPromotedInteger(N->getOperand(3));
+  switch (TLI.getExtendForAtomicCmpSwapArg()) {
+  case ISD::SIGN_EXTEND:
+    Op2 = SExtPromotedInteger(Op2);
+    break;
+  case ISD::ZERO_EXTEND:
+    Op2 = ZExtPromotedInteger(Op2);
+    break;
+  case ISD::ANY_EXTEND:
+    Op2 = GetPromotedInteger(Op2);
+    break;
+  default:
+    llvm_unreachable("Invalid atomic op extension");
+  }
+
   SDVTList VTs =
       DAG.getVTList(Op2.getValueType(), N->getValueType(1), MVT::Other);
   SDValue Res = DAG.getAtomicCmpSwap(

diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.h b/llvm/lib/Target/RISCV/RISCVISelLowering.h
index e2059e70831deb331b3bdd2edb2be23d0bde87e3..e0ca22dd201e89f61ca310602b03b03eb76cdb0f 100644 (file)
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.h
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.h
@@ -127,6 +127,10 @@ public:
     return ISD::SIGN_EXTEND;
   }
 
+  ISD::NodeType getExtendForAtomicCmpSwapArg() const override {
+    return ISD::SIGN_EXTEND;
+  }
+
   bool shouldExpandShift(SelectionDAG &DAG, SDNode *N) const override {
     if (DAG.getMachineFunction().getFunction().hasMinSize())
       return false;

diff --git a/llvm/test/CodeGen/RISCV/atomic-cmpxchg.ll b/llvm/test/CodeGen/RISCV/atomic-cmpxchg.ll
index a4526b7f46e769d64e0b524f97c408d585cc9561..6722b43cf65c656e419505fcf83a9829c0b6b6f9 100644 (file)
--- a/llvm/test/CodeGen/RISCV/atomic-cmpxchg.ll
+++ b/llvm/test/CodeGen/RISCV/atomic-cmpxchg.ll
@@ -1628,6 +1628,7 @@ define void @cmpxchg_i32_monotonic_monotonic(i32* %ptr, i32 %cmp, i32 %val) noun
 ;
 ; RV64IA-LABEL: cmpxchg_i32_monotonic_monotonic:
 ; RV64IA:       # %bb.0:
+; RV64IA-NEXT:    sext.w a1, a1
 ; RV64IA-NEXT:  .LBB20_1: # =>This Inner Loop Header: Depth=1
 ; RV64IA-NEXT:    lr.w a3, (a0)
 ; RV64IA-NEXT:    bne a3, a1, .LBB20_3
@@ -1680,6 +1681,7 @@ define void @cmpxchg_i32_acquire_monotonic(i32* %ptr, i32 %cmp, i32 %val) nounwi
 ;
 ; RV64IA-LABEL: cmpxchg_i32_acquire_monotonic:
 ; RV64IA:       # %bb.0:
+; RV64IA-NEXT:    sext.w a1, a1
 ; RV64IA-NEXT:  .LBB21_1: # =>This Inner Loop Header: Depth=1
 ; RV64IA-NEXT:    lr.w.aq a3, (a0)
 ; RV64IA-NEXT:    bne a3, a1, .LBB21_3
@@ -1732,6 +1734,7 @@ define void @cmpxchg_i32_acquire_acquire(i32* %ptr, i32 %cmp, i32 %val) nounwind
 ;
 ; RV64IA-LABEL: cmpxchg_i32_acquire_acquire:
 ; RV64IA:       # %bb.0:
+; RV64IA-NEXT:    sext.w a1, a1
 ; RV64IA-NEXT:  .LBB22_1: # =>This Inner Loop Header: Depth=1
 ; RV64IA-NEXT:    lr.w.aq a3, (a0)
 ; RV64IA-NEXT:    bne a3, a1, .LBB22_3
@@ -1784,6 +1787,7 @@ define void @cmpxchg_i32_release_monotonic(i32* %ptr, i32 %cmp, i32 %val) nounwi
 ;
 ; RV64IA-LABEL: cmpxchg_i32_release_monotonic:
 ; RV64IA:       # %bb.0:
+; RV64IA-NEXT:    sext.w a1, a1
 ; RV64IA-NEXT:  .LBB23_1: # =>This Inner Loop Header: Depth=1
 ; RV64IA-NEXT:    lr.w a3, (a0)
 ; RV64IA-NEXT:    bne a3, a1, .LBB23_3
@@ -1836,6 +1840,7 @@ define void @cmpxchg_i32_release_acquire(i32* %ptr, i32 %cmp, i32 %val) nounwind
 ;
 ; RV64IA-LABEL: cmpxchg_i32_release_acquire:
 ; RV64IA:       # %bb.0:
+; RV64IA-NEXT:    sext.w a1, a1
 ; RV64IA-NEXT:  .LBB24_1: # =>This Inner Loop Header: Depth=1
 ; RV64IA-NEXT:    lr.w a3, (a0)
 ; RV64IA-NEXT:    bne a3, a1, .LBB24_3
@@ -1888,6 +1893,7 @@ define void @cmpxchg_i32_acq_rel_monotonic(i32* %ptr, i32 %cmp, i32 %val) nounwi
 ;
 ; RV64IA-LABEL: cmpxchg_i32_acq_rel_monotonic:
 ; RV64IA:       # %bb.0:
+; RV64IA-NEXT:    sext.w a1, a1
 ; RV64IA-NEXT:  .LBB25_1: # =>This Inner Loop Header: Depth=1
 ; RV64IA-NEXT:    lr.w.aq a3, (a0)
 ; RV64IA-NEXT:    bne a3, a1, .LBB25_3
@@ -1940,6 +1946,7 @@ define void @cmpxchg_i32_acq_rel_acquire(i32* %ptr, i32 %cmp, i32 %val) nounwind
 ;
 ; RV64IA-LABEL: cmpxchg_i32_acq_rel_acquire:
 ; RV64IA:       # %bb.0:
+; RV64IA-NEXT:    sext.w a1, a1
 ; RV64IA-NEXT:  .LBB26_1: # =>This Inner Loop Header: Depth=1
 ; RV64IA-NEXT:    lr.w.aq a3, (a0)
 ; RV64IA-NEXT:    bne a3, a1, .LBB26_3
@@ -1992,6 +1999,7 @@ define void @cmpxchg_i32_seq_cst_monotonic(i32* %ptr, i32 %cmp, i32 %val) nounwi
 ;
 ; RV64IA-LABEL: cmpxchg_i32_seq_cst_monotonic:
 ; RV64IA:       # %bb.0:
+; RV64IA-NEXT:    sext.w a1, a1
 ; RV64IA-NEXT:  .LBB27_1: # =>This Inner Loop Header: Depth=1
 ; RV64IA-NEXT:    lr.w.aqrl a3, (a0)
 ; RV64IA-NEXT:    bne a3, a1, .LBB27_3
@@ -2044,6 +2052,7 @@ define void @cmpxchg_i32_seq_cst_acquire(i32* %ptr, i32 %cmp, i32 %val) nounwind
 ;
 ; RV64IA-LABEL: cmpxchg_i32_seq_cst_acquire:
 ; RV64IA:       # %bb.0:
+; RV64IA-NEXT:    sext.w a1, a1
 ; RV64IA-NEXT:  .LBB28_1: # =>This Inner Loop Header: Depth=1
 ; RV64IA-NEXT:    lr.w.aqrl a3, (a0)
 ; RV64IA-NEXT:    bne a3, a1, .LBB28_3
@@ -2096,6 +2105,7 @@ define void @cmpxchg_i32_seq_cst_seq_cst(i32* %ptr, i32 %cmp, i32 %val) nounwind
 ;
 ; RV64IA-LABEL: cmpxchg_i32_seq_cst_seq_cst:
 ; RV64IA:       # %bb.0:
+; RV64IA-NEXT:    sext.w a1, a1
 ; RV64IA-NEXT:  .LBB29_1: # =>This Inner Loop Header: Depth=1
 ; RV64IA-NEXT:    lr.w.aqrl a3, (a0)
 ; RV64IA-NEXT:    bne a3, a1, .LBB29_3