[RISCV][GISel] Make G_ICMP of pointers legal.

[reames]

LGTM

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

RISCVLegalizerInfo::RISCVLegalizerInfo(const RISCVSubtarget &ST) {
   }
 
   getActionDefinitionsBuilder({G_CONSTANT, G_IMPLICIT_DEF})
       .legalFor({XLenLLT, p0})
       .widenScalarToNextPow2(0)
       .clampScalar(0, XLenLLT, XLenLLT);
 
   getActionDefinitionsBuilder(G_ICMP)
-      .legalFor({{XLenLLT, XLenLLT}})
+      .legalFor({{XLenLLT, XLenLLT}, {XLenLLT, p0}})
       .widenScalarToNextPow2(1)
       .clampScalar(1, XLenLLT, XLenLLT)
       .clampScalar(0, XLenLLT, XLenLLT);
 
   getActionDefinitionsBuilder(G_SELECT)
       .legalFor({{XLenLLT, XLenLLT}, {p0, XLenLLT}})
       .widenScalarToNextPow2(0)
       .clampScalar(0, XLenLLT, XLenLLT)

llvm/test/CodeGen/RISCV/GlobalISel/legalizer/rv32/legalize-icmp.mir

bb.0.entry:
     %x:_(s64) = G_MERGE_VALUES %xhi(s32), %xlo(s32)
     %y:_(s64) = G_MERGE_VALUES %yhi(s32), %ylo(s32)
     %z:_(s1) = G_ICMP intpred(ne), %x, %y
     %z0:_(s32) = G_ANYEXT %z(s1)
     $x10 = COPY %z0(s32)
     PseudoRET implicit $x10
 
 ...
+---
+name:            cmp_eq_ptr
+body:             |
+  bb.0.entry:
+    ; CHECK-LABEL: name: cmp_eq_ptr
+    ; CHECK: [[COPY:%[0-9]+]]:_(p0) = COPY $x10
+    ; CHECK-NEXT: [[COPY1:%[0-9]+]]:_(p0) = COPY $x11
+    ; CHECK-NEXT: [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(eq), [[COPY]](p0), [[COPY1]]
+    ; CHECK-NEXT: $x10 = COPY [[ICMP]](s32)
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:_(p0) = COPY $x10
+    %1:_(p0) = COPY $x11
+    %2:_(s1) = G_ICMP intpred(eq), %0(p0), %1
+    %3:_(s32) = G_ANYEXT %2(s1)
+    $x10 = COPY %3(s32)
+    PseudoRET implicit $x10
+
+...

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

bb.0.entry:
     %x:_(s128) = G_MERGE_VALUES %xhi(s64), %xlo(s64)
     %y:_(s128) = G_MERGE_VALUES %yhi(s64), %ylo(s64)
     %z:_(s1) = G_ICMP intpred(ne), %x, %y
     %z0:_(s64) = G_ANYEXT %z(s1)
     $x10 = COPY %z0(s64)
     PseudoRET implicit $x10
 
 ...
+---
+name:            cmp_ne_ptr
+body:             |
+  bb.0.entry:
+    ; CHECK-LABEL: name: cmp_ne_ptr
+    ; CHECK: [[COPY:%[0-9]+]]:_(p0) = COPY $x10
+    ; CHECK-NEXT: [[COPY1:%[0-9]+]]:_(p0) = COPY $x11
+    ; CHECK-NEXT: [[ICMP:%[0-9]+]]:_(s64) = G_ICMP intpred(ne), [[COPY]](p0), [[COPY1]]
+    ; CHECK-NEXT: $x10 = COPY [[ICMP]](s64)
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:_(p0) = COPY $x10
+    %1:_(p0) = COPY $x11
+    %2:_(s1) = G_ICMP intpred(ne), %0(p0), %1
+    %3:_(s64) = G_ANYEXT %2(s1)
+    $x10 = COPY %3(s64)
+    PseudoRET implicit $x10
+
+...