[PATCH] D74857: [AMDGPU] simplifyI24 - replace GetDemandedBits with SimplifyMultipleUseDemandedBits

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added a reviewer: arsenm.
Herald added subscribers: kerbowa, hiraditya, t-tye, tpr, dstuttard, yaxunl, nhaehnle, wdng, jvesely, kzhuravl.
Herald added a project: LLVM.

GetDemandedBits mostly just calls SimplifyMultipleUseDemandedBits now, but it does a very blunt constant simplification that SimplifyMultipleUseDemandedBits avoids.

I think the changes in constants are correct (sign extended immediates are good?), otherwise we should really be handling this through ShrinkDemandedConstant/targetShrinkDemandedConstant.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D74857

Files:
  llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
  llvm/test/CodeGen/AMDGPU/amdgpu-mul24-knownbits.ll
  llvm/test/CodeGen/AMDGPU/lshl64-to-32.ll


Index: llvm/test/CodeGen/AMDGPU/lshl64-to-32.ll
===================================================================
--- llvm/test/CodeGen/AMDGPU/lshl64-to-32.ll
+++ llvm/test/CodeGen/AMDGPU/lshl64-to-32.ll
@@ -125,7 +125,7 @@
 ; GCN-NEXT:    v_mov_b32_e32 v4, v2
 ; GCN-NEXT:    s_waitcnt vmcnt(0)
 ; GCN-NEXT:    v_or_b32_e32 v0, 0x800000, v1
-; GCN-NEXT:    v_mul_i32_i24_e32 v0, 0xfffff9, v0
+; GCN-NEXT:    v_mul_i32_i24_e32 v0, -7, v0
 ; GCN-NEXT:    v_lshlrev_b32_e32 v1, 3, v0
 ; GCN-NEXT:    buffer_store_dwordx2 v[1:2], v[3:4], s[0:3], 0 addr64
 ; GCN-NEXT:    s_endpgm
Index: llvm/test/CodeGen/AMDGPU/amdgpu-mul24-knownbits.ll
===================================================================
--- llvm/test/CodeGen/AMDGPU/amdgpu-mul24-knownbits.ll
+++ llvm/test/CodeGen/AMDGPU/amdgpu-mul24-knownbits.ll
@@ -1,11 +1,11 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-
 ; RUN: llc -mtriple amdgcn-amd-amdhsa -mcpu=gfx900 < %s | FileCheck --check-prefix=GCN %s
+
 define weak_odr amdgpu_kernel void @test_mul24_knownbits_kernel(float addrspace(1)* %p) #4 {
 ; GCN-LABEL: test_mul24_knownbits_kernel:
 ; GCN:       ; %bb.0: ; %entry
 ; GCN-NEXT:    v_and_b32_e32 v0, 3, v0
-; GCN-NEXT:    v_mul_i32_i24_e32 v0, 0xfffffb, v0
+; GCN-NEXT:    v_mul_i32_i24_e32 v0, -5, v0
 ; GCN-NEXT:    s_load_dwordx2 s[0:1], s[4:5], 0x0
 ; GCN-NEXT:    v_and_b32_e32 v0, 0xffffffe0, v0
 ; GCN-NEXT:    v_ashrrev_i32_e32 v1, 31, v0
Index: llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
+++ llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
@@ -2813,6 +2813,7 @@
 static SDValue simplifyI24(SDNode *Node24,
                            TargetLowering::DAGCombinerInfo &DCI) {
   SelectionDAG &DAG = DCI.DAG;
+  const TargetLowering &TLI = DAG.getTargetLoweringInfo();
   bool IsIntrin = Node24->getOpcode() == ISD::INTRINSIC_WO_CHAIN;
 
   SDValue LHS = IsIntrin ? Node24->getOperand(1) : Node24->getOperand(0);
@@ -2826,11 +2827,11 @@
 
   APInt Demanded = APInt::getLowBitsSet(LHS.getValueSizeInBits(), 24);
 
-  // First try to simplify using GetDemandedBits which allows the operands to
-  // have other uses, but will only perform simplifications that involve
-  // bypassing some nodes for this user.
-  SDValue DemandedLHS = DAG.GetDemandedBits(LHS, Demanded);
-  SDValue DemandedRHS = DAG.GetDemandedBits(RHS, Demanded);
+  // First try to simplify using SimplifyMultipleUseDemandedBits which allows
+  // the operands to have other uses, but will only perform simplifications that
+  // involve bypassing some nodes for this user.
+  SDValue DemandedLHS = TLI.SimplifyMultipleUseDemandedBits(LHS, Demanded, DAG);
+  SDValue DemandedRHS = TLI.SimplifyMultipleUseDemandedBits(RHS, Demanded, DAG);
   if (DemandedLHS || DemandedRHS)
     return DAG.getNode(NewOpcode, SDLoc(Node24), Node24->getVTList(),
                        DemandedLHS ? DemandedLHS : LHS,
@@ -2838,7 +2839,6 @@
 
   // Now try SimplifyDemandedBits which can simplify the nodes used by our
   // operands if this node is the only user.
-  const TargetLowering &TLI = DAG.getTargetLoweringInfo();
   if (TLI.SimplifyDemandedBits(LHS, Demanded, DCI))
     return SDValue(Node24, 0);
   if (TLI.SimplifyDemandedBits(RHS, Demanded, DCI))


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