[InstCombine] Add tests for cttz of lowest set bit (NFC)

Author: nikic

llvm/test/Transforms/InstCombine/cttz.ll

@@ -2,6 +2,7 @@
 ; RUN: opt < %s -S -passes=instcombine | FileCheck %s
 
 declare i32 @llvm.cttz.i32(i32, i1)
+declare i32 @llvm.ctlz.i32(i32, i1)
 declare <2 x i64> @llvm.cttz.v2i64(<2 x i64>, i1)
 declare void @use(i32)
 
@@ -118,3 +119,109 @@ define <2 x i64> @cttz_sext_zero_def_vec(<2 x i32> %x) {
   %tz = tail call <2 x i64> @llvm.cttz.v2i64(<2 x i64> %s, i1 false)
   ret <2 x i64> %tz
 }
+
+define i32 @cttz_of_lowest_set_bit(i32 %x) {
+; CHECK-LABEL: @cttz_of_lowest_set_bit(
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[X:%.*]]
+; CHECK-NEXT:    [[AND:%.*]] = and i32 [[SUB]], [[X]]
+; CHECK-NEXT:    [[TZ:%.*]] = call i32 @llvm.cttz.i32(i32 [[AND]], i1 false), !range [[RNG1]]
+; CHECK-NEXT:    ret i32 [[TZ]]
+;
+  %sub = sub i32 0, %x
+  %and = and i32 %sub, %x
+  %tz = call i32 @llvm.cttz.i32(i32 %and, i1 false)
+  ret i32 %tz
+}
+
+define i32 @cttz_of_lowest_set_bit_commuted(i32 %xx) {
+; CHECK-LABEL: @cttz_of_lowest_set_bit_commuted(
+; CHECK-NEXT:    [[X:%.*]] = udiv i32 42, [[XX:%.*]]
+; CHECK-NEXT:    [[SUB:%.*]] = sub nsw i32 0, [[X]]
+; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X]], [[SUB]]
+; CHECK-NEXT:    [[TZ:%.*]] = call i32 @llvm.cttz.i32(i32 [[AND]], i1 false), !range [[RNG1]]
+; CHECK-NEXT:    ret i32 [[TZ]]
+;
+  %x = udiv i32 42, %xx ; thwart complexity-based canonicalization
+  %sub = sub i32 0, %x
+  %and = and i32 %x, %sub
+  %tz = call i32 @llvm.cttz.i32(i32 %and, i1 false)
+  ret i32 %tz
+}
+
+define i32 @cttz_of_lowest_set_bit_poison_flag(i32 %x) {
+; CHECK-LABEL: @cttz_of_lowest_set_bit_poison_flag(
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[X:%.*]]
+; CHECK-NEXT:    [[AND:%.*]] = and i32 [[SUB]], [[X]]
+; CHECK-NEXT:    [[TZ:%.*]] = call i32 @llvm.cttz.i32(i32 [[AND]], i1 true), !range [[RNG1]]
+; CHECK-NEXT:    ret i32 [[TZ]]
+;
+  %sub = sub i32 0, %x
+  %and = and i32 %sub, %x
+  %tz = call i32 @llvm.cttz.i32(i32 %and, i1 true)
+  ret i32 %tz
+}
+
+define <2 x i64> @cttz_of_lowest_set_bit_vec(<2 x i64> %x) {
+; CHECK-LABEL: @cttz_of_lowest_set_bit_vec(
+; CHECK-NEXT:    [[SUB:%.*]] = sub <2 x i64> zeroinitializer, [[X:%.*]]
+; CHECK-NEXT:    [[AND:%.*]] = and <2 x i64> [[SUB]], [[X]]
+; CHECK-NEXT:    [[TZ:%.*]] = call <2 x i64> @llvm.cttz.v2i64(<2 x i64> [[AND]], i1 false), !range [[RNG2]]
+; CHECK-NEXT:    ret <2 x i64> [[TZ]]
+;
+  %sub = sub <2 x i64> zeroinitializer, %x
+  %and = and <2 x i64> %sub, %x
+  %tz = call <2 x i64> @llvm.cttz.v2i64(<2 x i64> %and, i1 false)
+  ret <2 x i64> %tz
+}
+
+define <2 x i64> @cttz_of_lowest_set_bit_vec_undef(<2 x i64> %x) {
+; CHECK-LABEL: @cttz_of_lowest_set_bit_vec_undef(
+; CHECK-NEXT:    [[SUB:%.*]] = sub <2 x i64> zeroinitializer, [[X:%.*]]
+; CHECK-NEXT:    [[AND:%.*]] = and <2 x i64> [[SUB]], [[X]]
+; CHECK-NEXT:    [[TZ:%.*]] = call <2 x i64> @llvm.cttz.v2i64(<2 x i64> [[AND]], i1 false), !range [[RNG2]]
+; CHECK-NEXT:    ret <2 x i64> [[TZ]]
+;
+  %sub = sub <2 x i64> zeroinitializer, %x
+  %and = and <2 x i64> %sub, %x
+  %tz = call <2 x i64> @llvm.cttz.v2i64(<2 x i64> %and, i1 false)
+  ret <2 x i64> %tz
+}
+
+define i32 @cttz_of_lowest_set_bit_wrong_const(i32 %x) {
+; CHECK-LABEL: @cttz_of_lowest_set_bit_wrong_const(
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 1, [[X:%.*]]
+; CHECK-NEXT:    [[AND:%.*]] = and i32 [[SUB]], [[X]]
+; CHECK-NEXT:    [[TZ:%.*]] = call i32 @llvm.cttz.i32(i32 [[AND]], i1 false), !range [[RNG3:![0-9]+]]
+; CHECK-NEXT:    ret i32 [[TZ]]
+;
+  %sub = sub i32 1, %x
+  %and = and i32 %sub, %x
+  %tz = call i32 @llvm.cttz.i32(i32 %and, i1 false)
+  ret i32 %tz
+}
+
+define i32 @cttz_of_lowest_set_bit_wrong_operand(i32 %x, i32 %y) {
+; CHECK-LABEL: @cttz_of_lowest_set_bit_wrong_operand(
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[Y:%.*]]
+; CHECK-NEXT:    [[AND:%.*]] = and i32 [[SUB]], [[X:%.*]]
+; CHECK-NEXT:    [[TZ:%.*]] = call i32 @llvm.cttz.i32(i32 [[AND]], i1 false), !range [[RNG1]]
+; CHECK-NEXT:    ret i32 [[TZ]]
+;
+  %sub = sub i32 0, %y
+  %and = and i32 %sub, %x
+  %tz = call i32 @llvm.cttz.i32(i32 %and, i1 false)
+  ret i32 %tz
+}
+
+define i32 @cttz_of_lowest_set_bit_wrong_intrinsic(i32 %x) {
+; CHECK-LABEL: @cttz_of_lowest_set_bit_wrong_intrinsic(
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[X:%.*]]
+; CHECK-NEXT:    [[AND:%.*]] = and i32 [[SUB]], [[X]]
+; CHECK-NEXT:    [[TZ:%.*]] = call i32 @llvm.ctlz.i32(i32 [[AND]], i1 false), !range [[RNG1]]
+; CHECK-NEXT:    ret i32 [[TZ]]
+;
+  %sub = sub i32 0, %x
+  %and = and i32 %sub, %x
+  %tz = call i32 @llvm.ctlz.i32(i32 %and, i1 false)
+  ret i32 %tz
+}