[NFC][testcases] add testcases for folding srem whose operands are negatived.

Finish same optimization for add instruction in D49216 and sdiv instruction in 
D49382. This patch is for srem instruction.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@337270 91177308-0d34-0410-b5e6-96231b3b80d8

Author: Chen Zheng

test/Transforms/InstSimplify/srem.ll

@@ -0,0 +1,49 @@
+; RUN: opt < %s -instsimplify -S | FileCheck %s
+
+define i32 @negated_operand(i32 %x) {
+; CHECK-LABEL: @negated_operand(
+; CHECK-NEXT:    [[NEGX:%.*]] = sub i32 0, [[X:%.*]]
+; CHECK-NEXT:    [[REM:%.*]] = srem i32 [[NEGX]], [[X]]
+; CHECK-NEXT:    ret i32 [[REM]]
+;
+  %negx = sub i32 0, %x
+  %rem = srem i32 %negx, %x
+  ret i32 %rem
+}
+
+define <2 x i32> @negated_operand_commute_vec(<2 x i32> %x) {
+; CHECK-LABEL: @negated_operand_commute_vec(
+; CHECK-NEXT:    [[NEGX:%.*]] = sub nsw <2 x i32> zeroinitializer, [[X:%.*]]
+; CHECK-NEXT:    [[REM:%.*]] = srem <2 x i32> [[NEGX]], [[X]]
+; CHECK-NEXT:    ret <2 x i32> [[REM]]
+;
+  %negx = sub nsw <2 x i32> zeroinitializer, %x
+  %rem = srem <2 x i32> %negx, %x
+  ret <2 x i32> %rem
+}
+
+define i32 @knownnegation(i32 %x, i32 %y) {
+; CHECK-LABEL: @knownnegation(
+; CHECK-NEXT:    [[XY:%.*]] = sub nsw i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[YX:%.*]] = sub nsw i32 [[Y]], [[X]]
+; CHECK-NEXT:    [[REM:%.*]] = srem i32 [[XY]], [[YX]]
+; CHECK-NEXT:    ret i32 [[REM]]
+;
+  %xy = sub nsw i32 %x, %y
+  %yx = sub nsw i32 %y, %x
+  %rem = srem i32 %xy, %yx
+  ret i32 %rem
+}
+
+define <2 x i32> @knownnegation_commute_vec(<2 x i32> %x, <2 x i32> %y) {
+; CHECK-LABEL: @knownnegation_commute_vec(
+; CHECK-NEXT:    [[XY:%.*]] = sub nsw <2 x i32> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[YX:%.*]] = sub nsw <2 x i32> [[Y]], [[X]]
+; CHECK-NEXT:    [[REM:%.*]] = srem <2 x i32> [[XY]], [[YX]]
+; CHECK-NEXT:    ret <2 x i32> [[REM]]
+;
+  %xy = sub nsw <2 x i32> %x, %y
+  %yx = sub nsw <2 x i32> %y, %x
+  %rem = srem <2 x i32> %xy, %yx
+  ret <2 x i32> %rem
+}