Add test to check we can instcombine after reassociate. NFC.

The pattern became optimized after b92412f.

Differential Revision: https://reviews.llvm.org/D112258

Author: rampitec

llvm/test/Transforms/PhaseOrdering/reassociate-instcombine.ll

@@ -0,0 +1,38 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -O1 -S < %s | FileCheck %s
+
+; Make sure we reassociate and1 with and2 before instcombine to allow
+; Demorgan logic fold:
+; (a & ~b) & ~c --> a & ~(b | c)
+define i4 @not_reassociate_and_and_not(i4 %a, i4 %b, i4 %c, i4 %d) {
+; CHECK-LABEL: @not_reassociate_and_and_not(
+; CHECK-NEXT:    [[TMP1:%.*]] = or i4 [[B:%.*]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = xor i4 [[TMP1]], -1
+; CHECK-NEXT:    [[AND2:%.*]] = and i4 [[TMP2]], [[A:%.*]]
+; CHECK-NEXT:    [[AND3:%.*]] = and i4 [[AND2]], [[D:%.*]]
+; CHECK-NEXT:    ret i4 [[AND3]]
+;
+  %notb = xor i4 %b, -1
+  %notc = xor i4 %c, -1
+  %and1 = and i4 %a, %notb
+  %and2 = and i4 %and1, %d
+  %and3 = and i4 %and2, %notc
+  ret i4 %and3
+}
+
+; (a | ~b) | ~c --> a | ~(b & c)
+define i32 @not_reassociate_or_or_not(i32 %a, i32 %b, i32 %c, i32 %d) {
+; CHECK-LABEL: @not_reassociate_or_or_not(
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[B:%.*]], [[C:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = xor i32 [[TMP1]], -1
+; CHECK-NEXT:    [[B2:%.*]] = or i32 [[TMP2]], [[A:%.*]]
+; CHECK-NEXT:    [[B3:%.*]] = or i32 [[B2]], [[D:%.*]]
+; CHECK-NEXT:    ret i32 [[B3]]
+;
+  %notb = xor i32 %b, -1
+  %notc = xor i32 %c, -1
+  %b1 = or i32 %a, %notb
+  %b2 = or i32 %b1, %d
+  %b3 = or i32 %b2, %notc
+  ret i32 %b3
+}