[GlobalISel] Add computeNumSignBits for ASHR

Author: davemgreen

llvm/lib/CodeGen/GlobalISel/GISelValueTracking.cpp

@@ -864,6 +864,16 @@ unsigned GISelValueTracking::computeNumSignBits(Register R,
       return TyBits - 1; // Every always-zero bit is a sign bit.
     break;
   }
+  case TargetOpcode::G_ASHR: {
+    Register Src1 = MI.getOperand(1).getReg();
+    Register Src2 = MI.getOperand(2).getReg();
+    LLT SrcTy = MRI.getType(Src1);
+    FirstAnswer = computeNumSignBits(Src1, DemandedElts, Depth + 1);
+    if (auto C = getIConstantSplatVal(Src2, MRI))
+      FirstAnswer = std::max<uint64_t>(FirstAnswer + C->getZExtValue(),
+                                       SrcTy.getScalarSizeInBits());
+    break;
+  }
   case TargetOpcode::G_INTRINSIC:
   case TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS:
   case TargetOpcode::G_INTRINSIC_CONVERGENT:

llvm/test/CodeGen/AArch64/aarch64-smull.ll

@@ -2265,68 +2265,25 @@ define <2 x i64> @lsr_const(<2 x i64> %a, <2 x i64> %b) {
 }
 
 define <2 x i64> @asr(<2 x i64> %a, <2 x i64> %b) {
-; CHECK-NEON-LABEL: asr:
-; CHECK-NEON:       // %bb.0:
-; CHECK-NEON-NEXT:    shrn v0.2s, v0.2d, #32
-; CHECK-NEON-NEXT:    shrn v1.2s, v1.2d, #32
-; CHECK-NEON-NEXT:    smull v0.2d, v0.2s, v1.2s
-; CHECK-NEON-NEXT:    ret
-;
-; CHECK-SVE-LABEL: asr:
-; CHECK-SVE:       // %bb.0:
-; CHECK-SVE-NEXT:    shrn v0.2s, v0.2d, #32
-; CHECK-SVE-NEXT:    shrn v1.2s, v1.2d, #32
-; CHECK-SVE-NEXT:    smull v0.2d, v0.2s, v1.2s
-; CHECK-SVE-NEXT:    ret
-;
-; CHECK-GI-LABEL: asr:
-; CHECK-GI:       // %bb.0:
-; CHECK-GI-NEXT:    sshr v0.2d, v0.2d, #32
-; CHECK-GI-NEXT:    sshr v1.2d, v1.2d, #32
-; CHECK-GI-NEXT:    fmov x8, d0
-; CHECK-GI-NEXT:    fmov x9, d1
-; CHECK-GI-NEXT:    mov x10, v0.d[1]
-; CHECK-GI-NEXT:    mov x11, v1.d[1]
-; CHECK-GI-NEXT:    mul x8, x8, x9
-; CHECK-GI-NEXT:    mul x9, x10, x11
-; CHECK-GI-NEXT:    mov v0.d[0], x8
-; CHECK-GI-NEXT:    mov v0.d[1], x9
-; CHECK-GI-NEXT:    ret
+; CHECK-LABEL: asr:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    shrn v0.2s, v0.2d, #32
+; CHECK-NEXT:    shrn v1.2s, v1.2d, #32
+; CHECK-NEXT:    smull v0.2d, v0.2s, v1.2s
+; CHECK-NEXT:    ret
     %x = ashr <2 x i64> %a, <i64 32, i64 32>
     %y = ashr <2 x i64> %b, <i64 32, i64 32>
     %z = mul nsw <2 x i64> %x, %y
     ret <2 x i64> %z
 }
 
 define <2 x i64> @asr_const(<2 x i64> %a, <2 x i64> %b) {
-; CHECK-NEON-LABEL: asr_const:
-; CHECK-NEON:       // %bb.0:
-; CHECK-NEON-NEXT:    movi v1.2s, #31
-; CHECK-NEON-NEXT:    shrn v0.2s, v0.2d, #32
-; CHECK-NEON-NEXT:    smull v0.2d, v0.2s, v1.2s
-; CHECK-NEON-NEXT:    ret
-;
-; CHECK-SVE-LABEL: asr_const:
-; CHECK-SVE:       // %bb.0:
-; CHECK-SVE-NEXT:    movi v1.2s, #31
-; CHECK-SVE-NEXT:    shrn v0.2s, v0.2d, #32
-; CHECK-SVE-NEXT:    smull v0.2d, v0.2s, v1.2s
-; CHECK-SVE-NEXT:    ret
-;
-; CHECK-GI-LABEL: asr_const:
-; CHECK-GI:       // %bb.0:
-; CHECK-GI-NEXT:    adrp x8, .LCPI81_0
-; CHECK-GI-NEXT:    sshr v0.2d, v0.2d, #32
-; CHECK-GI-NEXT:    ldr q1, [x8, :lo12:.LCPI81_0]
-; CHECK-GI-NEXT:    fmov x8, d0
-; CHECK-GI-NEXT:    fmov x9, d1
-; CHECK-GI-NEXT:    mov x10, v0.d[1]
-; CHECK-GI-NEXT:    mov x11, v1.d[1]
-; CHECK-GI-NEXT:    mul x8, x8, x9
-; CHECK-GI-NEXT:    mul x9, x10, x11
-; CHECK-GI-NEXT:    mov v0.d[0], x8
-; CHECK-GI-NEXT:    mov v0.d[1], x9
-; CHECK-GI-NEXT:    ret
+; CHECK-LABEL: asr_const:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    movi v1.2s, #31
+; CHECK-NEXT:    shrn v0.2s, v0.2d, #32
+; CHECK-NEXT:    smull v0.2d, v0.2s, v1.2s
+; CHECK-NEXT:    ret
     %x = ashr <2 x i64> %a, <i64 32, i64 32>
     %z = mul nsw <2 x i64> %x, <i64 31, i64 31>
     ret <2 x i64> %z

llvm/test/CodeGen/RISCV/GlobalISel/legalizer/legalize-abs-rv64.mir

@@ -88,8 +88,7 @@ body:             |
     ; RV64I-NEXT: [[ADD:%[0-9]+]]:_(s64) = G_ADD [[ASSERT_SEXT]], [[ASHR]]
     ; RV64I-NEXT: [[SEXT_INREG:%[0-9]+]]:_(s64) = G_SEXT_INREG [[ADD]], 32
     ; RV64I-NEXT: [[XOR:%[0-9]+]]:_(s64) = G_XOR [[SEXT_INREG]], [[ASHR]]
-    ; RV64I-NEXT: [[SEXT_INREG1:%[0-9]+]]:_(s64) = G_SEXT_INREG [[XOR]], 32
-    ; RV64I-NEXT: $x10 = COPY [[SEXT_INREG1]](s64)
+    ; RV64I-NEXT: $x10 = COPY [[XOR]](s64)
     ; RV64I-NEXT: PseudoRET implicit $x10
     ;
     ; RV64ZBB-LABEL: name: abs_i32

llvm/test/CodeGen/RISCV/GlobalISel/rv64zbb.ll

@@ -1053,9 +1053,8 @@ define signext i32 @abs_i32_sext(i32 signext %x) {
 ; RV64I-LABEL: abs_i32_sext:
 ; RV64I:       # %bb.0:
 ; RV64I-NEXT:    srai a1, a0, 31
-; RV64I-NEXT:    add a0, a0, a1
+; RV64I-NEXT:    addw a0, a0, a1
 ; RV64I-NEXT:    xor a0, a0, a1
-; RV64I-NEXT:    sext.w a0, a0
 ; RV64I-NEXT:    ret
 ;
 ; RV64ZBB-LABEL: abs_i32_sext: