[RISCV][GISel] Support G_CTPOP with Zbb.

Author: topperc

llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp

@@ -105,11 +105,21 @@ RISCVLegalizerInfo::RISCVLegalizerInfo(const RISCVSubtarget &ST)
     BSwap.maxScalar(0, sXLen).lower();
 
   getActionDefinitionsBuilder(
-      {G_CTPOP, G_CTLZ, G_CTLZ_ZERO_UNDEF, G_CTTZ, G_CTTZ_ZERO_UNDEF})
+      {G_CTLZ, G_CTLZ_ZERO_UNDEF, G_CTTZ, G_CTTZ_ZERO_UNDEF})
       .maxScalar(0, sXLen)
       .scalarSameSizeAs(1, 0)
       .lower();
 
+  auto &CTPOPActions = getActionDefinitionsBuilder(G_CTPOP);
+  if (ST.hasStdExtZbb()) {
+    CTPOPActions.legalFor({{s32, s32}, {sXLen, sXLen}})
+        .clampScalar(0, s32, sXLen)
+        .widenScalarToNextPow2(0)
+        .scalarSameSizeAs(1, 0);
+  } else {
+    CTPOPActions.maxScalar(0, sXLen).scalarSameSizeAs(1, 0).lower();
+  }
+
   getActionDefinitionsBuilder({G_CONSTANT, G_IMPLICIT_DEF})
       .legalFor({s32, sXLen, p0})
       .widenScalarToNextPow2(0)

llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/ctpop-rv32.mir

@@ -0,0 +1,22 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=riscv32 -mattr=+zbb -run-pass=instruction-select \
+# RUN:   -simplify-mir -verify-machineinstrs %s -o - \
+# RUN:   | FileCheck -check-prefix=RV32I %s
+
+---
+name:            ctpop_s32
+legalized:       true
+regBankSelected: true
+body:             |
+  bb.0.entry:
+    ; RV32I-LABEL: name: ctpop_s32
+    ; RV32I: [[COPY:%[0-9]+]]:gpr = COPY $x10
+    ; RV32I-NEXT: [[CPOP:%[0-9]+]]:gpr = CPOP [[COPY]]
+    ; RV32I-NEXT: $x10 = COPY [[CPOP]]
+    ; RV32I-NEXT: PseudoRET implicit $x10
+    %0:gprb(s32) = COPY $x10
+    %1:gprb(s32) = G_CTPOP %0
+    $x10 = COPY %1(s32)
+    PseudoRET implicit $x10
+
+...

llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/ctpop-rv64.mir

@@ -0,0 +1,41 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=riscv64 -mattr=+zbb -run-pass=instruction-select \
+# RUN:   -simplify-mir -verify-machineinstrs %s -o - \
+# RUN:   | FileCheck -check-prefix=RV64I %s
+
+---
+name:            ctpop_s32
+legalized:       true
+regBankSelected: true
+body:             |
+  bb.0.entry:
+    ; RV64I-LABEL: name: ctpop_s32
+    ; RV64I: [[COPY:%[0-9]+]]:gpr = COPY $x10
+    ; RV64I-NEXT: [[CPOPW:%[0-9]+]]:gpr = CPOPW [[COPY]]
+    ; RV64I-NEXT: $x10 = COPY [[CPOPW]]
+    ; RV64I-NEXT: PseudoRET implicit $x10
+    %0:gprb(s64) = COPY $x10
+    %1:gprb(s32) = G_TRUNC %0
+    %2:gprb(s32) = G_CTPOP %1
+    %3:gprb(s64) = G_ANYEXT %2
+    $x10 = COPY %3(s64)
+    PseudoRET implicit $x10
+
+...
+---
+name:            ctpop_s64
+legalized:       true
+regBankSelected: true
+body:             |
+  bb.0.entry:
+    ; RV64I-LABEL: name: ctpop_s64
+    ; RV64I: [[COPY:%[0-9]+]]:gpr = COPY $x10
+    ; RV64I-NEXT: [[CPOP:%[0-9]+]]:gpr = CPOP [[COPY]]
+    ; RV64I-NEXT: $x10 = COPY [[CPOP]]
+    ; RV64I-NEXT: PseudoRET implicit $x10
+    %0:gprb(s64) = COPY $x10
+    %1:gprb(s64) = G_CTPOP %0
+    $x10 = COPY %1(s64)
+    PseudoRET implicit $x10
+
+...