[GlobalISel] Add G_ABS computeKnownBits

llvm/lib/CodeGen/GlobalISel/GISelValueTracking.cpp

@@ -675,6 +675,14 @@ void GISelValueTracking::computeKnownBitsImpl(Register R, KnownBits &Known,
     }
     break;
   }
+  case TargetOpcode::G_ABS: {
+    Register SrcReg = MI.getOperand(1).getReg();
+    computeKnownBitsImpl(SrcReg, Known, DemandedElts, Depth + 1);
+    Known = Known.abs();
+    Known.Zero.setHighBits(computeNumSignBits(SrcReg, DemandedElts, Depth + 1) -
+                           1);
+    break;
+  }
   }
 
   LLVM_DEBUG(dumpResult(MI, Known, Depth));

llvm/test/CodeGen/AArch64/GlobalISel/knownbits-abs.mir

@@ -0,0 +1,83 @@
+# NOTE: Assertions have been autogenerated by utils/update_givaluetracking_test_checks.py UTC_ARGS: --version 5
+# RUN: llc -mtriple=aarch64 -passes='print<gisel-value-tracking>' -filetype=null %s 2>&1 | FileCheck %s
+
+---
+name: Cst
+body: |
+  bb.0:
+  ; CHECK-LABEL: name: @Cst
+  ; CHECK-NEXT: %0:_ KnownBits:00010011 SignBits:3
+  ; CHECK-NEXT: %1:_ KnownBits:00010011 SignBits:3
+    %0:_(s8) = G_CONSTANT i8 19
+    %1:_(s8) = G_ABS %0
+...
+---
+name: CstNeg
+body: |
+  bb.0:
+  ; CHECK-LABEL: name: @CstNeg
+  ; CHECK-NEXT: %0:_ KnownBits:11101110 SignBits:3
+  ; CHECK-NEXT: %1:_ KnownBits:00010010 SignBits:3
+    %0:_(s8) = G_CONSTANT i8 238
+    %1:_(s8) = G_ABS %0
+...
+---
+name: SplatVecCst
+body: |
+  bb.0:
+  ; CHECK-LABEL: name: @SplatVecCst
+  ; CHECK-NEXT: %0:_ KnownBits:11111010 SignBits:5
+  ; CHECK-NEXT: %1:_ KnownBits:11111010 SignBits:5
+  ; CHECK-NEXT: %2:_ KnownBits:00000110 SignBits:5
+    %0:_(s8) = G_CONSTANT i8 250
+    %1:_(<vscale x 16 x s8>) = G_SPLAT_VECTOR %0(s8)
+    %2:_(<vscale x 16 x s8>) = G_ABS %1
+...
+---
+name: VecCst
+body: |
+  bb.0:
+  ; CHECK-LABEL: name: @VecCst
+  ; CHECK-NEXT: %0:_ KnownBits:00011001 SignBits:3
+  ; CHECK-NEXT: %1:_ KnownBits:11100001 SignBits:3
+  ; CHECK-NEXT: %2:_ KnownBits:?????001 SignBits:3
+  ; CHECK-NEXT: %3:_ KnownBits:00?????1 SignBits:2
+    %0:_(s8) = G_CONSTANT i8 25
+    %1:_(s8) = G_CONSTANT i8 225
+    %2:_(<2 x s8>) = G_BUILD_VECTOR %0:_(s8), %1:_(s8)
+    %3:_(<2 x s8>) = G_ABS %2
+...
+---
+name: ImplicitDef
+body: |
+  bb.0:
+  ; CHECK-LABEL: name: @ImplicitDef
+  ; CHECK-NEXT: %0:_ KnownBits:???????? SignBits:1
+  ; CHECK-NEXT: %1:_ KnownBits:???????? SignBits:1
+    %0:_(s8) = G_IMPLICIT_DEF
+    %1:_(s8) = G_ABS %0
+...
+---
+name: CstSext
+body: |
+  bb.0:
+  ; CHECK-LABEL: name: @CstSext
+  ; CHECK-NEXT: %0:_ KnownBits:11000111 SignBits:2
+  ; CHECK-NEXT: %1:_ KnownBits:1111111111000111 SignBits:10
+  ; CHECK-NEXT: %2:_ KnownBits:0000000000111001 SignBits:10
+    %0:_(s8) = G_CONSTANT i8 199
+    %1:_(s16) = G_SEXT %0
+    %2:_(s16) = G_ABS %1
+...
+---
+name: ImplicitDefSext
+body: |
+  bb.0:
+  ; CHECK-LABEL: name: @ImplicitDefSext
+  ; CHECK-NEXT: %0:_ KnownBits:???????? SignBits:1
+  ; CHECK-NEXT: %1:_ KnownBits:???????????????? SignBits:9
+  ; CHECK-NEXT: %2:_ KnownBits:00000000???????? SignBits:8
+    %0:_(s8) = G_IMPLICIT_DEF
+    %1:_(s16) = G_SEXT %0
+    %2:_(s16) = G_ABS %1
+...