[llvm] [ConstantRange] Handle `Intrinsic::cttz` and `Intrinsic::ctpop` (PR #67917)

[via llvm-commits]

================
@@ -1010,6 +1010,60 @@ else:
   ret i1 %res2
 }
 
+define i1 @cttz_fold(i16 %x) {
+; CHECK-LABEL: @cttz_fold(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i16 [[X:%.*]], 256
+; CHECK-NEXT:    br i1 [[CMP]], label [[IF:%.*]], label [[ELSE:%.*]]
+; CHECK:       if:
+; CHECK-NEXT:    [[CTTZ:%.*]] = call i16 @llvm.cttz.i16(i16 [[X]], i1 true)
+; CHECK-NEXT:    ret i1 false
+; CHECK:       else:
+; CHECK-NEXT:    [[CTTZ2:%.*]] = call i16 @llvm.cttz.i16(i16 [[X]], i1 true)
+; CHECK-NEXT:    [[RES2:%.*]] = icmp ult i16 [[CTTZ2]], 8
+; CHECK-NEXT:    ret i1 [[RES2]]
+;
+  %cmp = icmp ult i16 %x, 256
+  br i1 %cmp, label %if, label %else
+
+if:
+  %cttz = call i16 @llvm.cttz.i16(i16 %x, i1 true)
+  %res = icmp uge i16 %cttz, 8
+  ret i1 %res
+
+else:
+  %cttz2 = call i16 @llvm.cttz.i16(i16 %x, i1 true)
+  %res2 = icmp ult i16 %cttz2, 8
+  ret i1 %res2
+}
+
+define i1 @ctpop_fold(i16 %x) {
+; CHECK-LABEL: @ctpop_fold(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i16 [[X:%.*]], 256
+; CHECK-NEXT:    br i1 [[CMP]], label [[IF:%.*]], label [[ELSE:%.*]]
+; CHECK:       if:
+; CHECK-NEXT:    [[CTPOP:%.*]] = call i16 @llvm.ctpop.i16(i16 [[X]])
+; CHECK-NEXT:    ret i1 true
+; CHECK:       else:
+; CHECK-NEXT:    [[CTPOP2:%.*]] = call i16 @llvm.ctpop.i16(i16 [[X]])
+; CHECK-NEXT:    [[RES2:%.*]] = icmp ugt i16 [[CTPOP2]], 8
+; CHECK-NEXT:    ret i1 [[RES2]]
+;
+  %cmp = icmp ult i16 %x, 256
+  br i1 %cmp, label %if, label %else
+
+if:
+  %ctpop = call i16 @llvm.ctpop.i16(i16 %x)
+  %res = icmp ule i16 %ctpop, 8
+  ret i1 %res
+
+else:
+  %ctpop2 = call i16 @llvm.ctpop.i16(i16 %x)
+  %res2 = icmp ugt i16 %ctpop2, 8
+  ret i1 %res2
+}
+
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goldsteinn wrote:

As per usual, please precommit tests.

https://github.com/llvm/llvm-project/pull/67917