[PATCH] D47702: DAG: ComputeNumSignBits from load range metadata

[Matt Arsenault via Phabricator via llvm-commits]

arsenm updated this revision to Diff 475637.
arsenm edited the summary of this revision.
arsenm added a comment.
Herald added subscribers: kosarev, hiraditya.
Herald added projects: LLVM, All.

Rebase, on top of baseline test commit. Also try to handle the unequal result size case, though poorly tested


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D47702/new/

https://reviews.llvm.org/D47702

Files:
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  llvm/test/CodeGen/AMDGPU/load-range-metadata-sign-bits.ll


Index: llvm/test/CodeGen/AMDGPU/load-range-metadata-sign-bits.ll
===================================================================
--- llvm/test/CodeGen/AMDGPU/load-range-metadata-sign-bits.ll
+++ llvm/test/CodeGen/AMDGPU/load-range-metadata-sign-bits.ll
@@ -7,7 +7,6 @@
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
 ; GCN-NEXT:    global_load_dword v0, v[0:1], off glc
 ; GCN-NEXT:    s_waitcnt vmcnt(0)
-; GCN-NEXT:    v_bfe_i32 v0, v0, 0, 8
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %val = load volatile i32, ptr addrspace(1) %ptr, align 4, !range !0 ; [-127, 128)
   %shl = shl i32 %val, 24
@@ -61,11 +60,8 @@
 ; GCN-LABEL: range_metadata_sextload_i8_signed_range_i4_i32:
 ; GCN:       ; %bb.0:
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; GCN-NEXT:    global_load_ubyte v0, v[0:1], off glc
+; GCN-NEXT:    global_load_sbyte v0, v[0:1], off glc
 ; GCN-NEXT:    s_waitcnt vmcnt(0)
-; GCN-NEXT:    v_lshlrev_b16_e32 v0, 11, v0
-; GCN-NEXT:    v_ashrrev_i16_e32 v0, 11, v0
-; GCN-NEXT:    v_bfe_i32 v0, v0, 0, 16
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %load = load volatile i8, ptr addrspace(1) %ptr, align 1, !range !4
   %shl = shl i8 %load, 3
@@ -94,7 +90,6 @@
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
 ; GCN-NEXT:    global_load_dword v0, v[0:1], off glc
 ; GCN-NEXT:    s_waitcnt vmcnt(0)
-; GCN-NEXT:    v_bfe_i32 v0, v0, 0, 1
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %val = load volatile i32, ptr addrspace(1) %ptr, align 4, !range !6
   %shl = shl i32 %val, 31
@@ -123,8 +118,6 @@
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
 ; GCN-NEXT:    global_load_dwordx2 v[0:1], v[0:1], off glc
 ; GCN-NEXT:    s_waitcnt vmcnt(0)
-; GCN-NEXT:    v_lshlrev_b64 v[0:1], 31, v[0:1]
-; GCN-NEXT:    v_ashrrev_i64 v[0:1], 31, v[0:1]
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %val = load volatile i64, ptr addrspace(1) %ptr, align 4, !range !7
   %shl = shl i64 %val, 31
@@ -138,8 +131,6 @@
 ; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
 ; GCN-NEXT:    global_load_dwordx2 v[0:1], v[0:1], off glc
 ; GCN-NEXT:    s_waitcnt vmcnt(0)
-; GCN-NEXT:    v_lshlrev_b64 v[0:1], 30, v[0:1]
-; GCN-NEXT:    v_ashrrev_i64 v[0:1], 30, v[0:1]
 ; GCN-NEXT:    s_setpc_b64 s[30:31]
   %val = load volatile i64, ptr addrspace(1) %ptr, align 4, !range !8
   %shl = shl i64 %val, 30
Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -46,6 +46,7 @@
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
 #include "llvm/CodeGen/ValueTypes.h"
 #include "llvm/IR/Constant.h"
+#include "llvm/IR/ConstantRange.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DebugInfoMetadata.h"
@@ -4406,6 +4407,34 @@
     assert(Tmp <= VTBits && "Failed to determine minimum sign bits");
     return Tmp;
   }
+  case ISD::LOAD: {
+    LoadSDNode *LD = cast<LoadSDNode>(Op);
+    if (const MDNode *Ranges = LD->getRanges()) {
+      if (DemandedElts != 1)
+        break;
+
+      ConstantRange CR = getConstantRangeFromMetadata(*Ranges);
+      if (VTBits > CR.getBitWidth()) {
+        switch (LD->getExtensionType()) {
+        case ISD::SEXTLOAD:
+          CR = CR.signExtend(VTBits);
+          break;
+        case ISD::ZEXTLOAD:
+          CR = CR.zeroExtend(VTBits);
+          break;
+        default:
+          break;
+        }
+      }
+
+      if (VTBits != CR.getBitWidth())
+        break;
+      return std::min(CR.getSignedMin().getNumSignBits(),
+                      CR.getSignedMax().getNumSignBits());
+    }
+
+    break;
+  }
   case ISD::ATOMIC_CMP_SWAP:
   case ISD::ATOMIC_CMP_SWAP_WITH_SUCCESS:
   case ISD::ATOMIC_SWAP:


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