[NFC][InstCombine] Add some tests with sdiv-by-negative-power-of-two

Author: LebedevRI

llvm/test/Transforms/InstCombine/sdiv-of-non-negative-by-negative-power-of-two.ll

@@ -0,0 +1,47 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt %s -instcombine -S | FileCheck %s
+
+; Fold
+;   x s/ (-1 << y)
+; to
+;   -(x >> y)
+; iff x is known non-negative.
+
+declare void @llvm.assume(i1)
+
+define i8 @t0(i8 %x, i8 %y) {
+; CHECK-LABEL: @t0(
+; CHECK-NEXT:    [[X_IS_NONNEGATIVE:%.*]] = icmp sgt i8 [[X:%.*]], -1
+; CHECK-NEXT:    call void @llvm.assume(i1 [[X_IS_NONNEGATIVE]])
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i8 [[X]], -32
+; CHECK-NEXT:    ret i8 [[DIV]]
+;
+  %x_is_nonnegative = icmp sge i8 %x, 0
+  call void @llvm.assume(i1 %x_is_nonnegative)
+  %div = sdiv i8 %x, -32
+  ret i8 %div
+}
+define i8 @n1(i8 %x, i8 %y) {
+; CHECK-LABEL: @n1(
+; CHECK-NEXT:    [[X_IS_NONNEGATIVE:%.*]] = icmp sgt i8 [[X:%.*]], -2
+; CHECK-NEXT:    call void @llvm.assume(i1 [[X_IS_NONNEGATIVE]])
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i8 [[X]], -32
+; CHECK-NEXT:    ret i8 [[DIV]]
+;
+  %x_is_nonnegative = icmp sge i8 %x, -1 ; could be negative
+  call void @llvm.assume(i1 %x_is_nonnegative)
+  %div = sdiv i8 %x, -32
+  ret i8 %div
+}
+define i8 @n2(i8 %x, i8 %y) {
+; CHECK-LABEL: @n2(
+; CHECK-NEXT:    [[X_IS_NONNEGATIVE:%.*]] = icmp sgt i8 [[X:%.*]], -1
+; CHECK-NEXT:    call void @llvm.assume(i1 [[X_IS_NONNEGATIVE]])
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i8 [[X]], -31
+; CHECK-NEXT:    ret i8 [[DIV]]
+;
+  %x_is_nonnegative = icmp sge i8 %x, 0
+  call void @llvm.assume(i1 %x_is_nonnegative)
+  %div = sdiv i8 %x, -31 ; not a negative power of two
+  ret i8 %div
+}