[llvm] [SeparateConstOffsetFromGEP] Decompose constant xor operand if possible (PR #135788)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,154 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -mtriple=amdgcn-amd-amdhsa -passes=separate-const-offset-from-gep \
+; RUN: -S < %s | FileCheck %s
+
+
+; Test a simple case of xor to or disjoint transformation
+define void @test_basic_transformation(ptr %ptr, i64 %input) {
+; CHECK-LABEL: define void @test_basic_transformation(
+; CHECK-SAME: ptr [[PTR:%.*]], i64 [[INPUT:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[BASE:%.*]] = and i64 [[INPUT]], -8192
+; CHECK-NEXT:    [[ADDR1:%.*]] = xor i64 [[BASE]], 32
+; CHECK-NEXT:    [[ADDR2_OR_DISJOINT:%.*]] = or disjoint i64 [[ADDR1]], 2048
+; CHECK-NEXT:    [[ADDR3_OR_DISJOINT:%.*]] = or disjoint i64 [[ADDR1]], 4096
+; CHECK-NEXT:    [[GEP1:%.*]] = getelementptr i8, ptr [[PTR]], i64 [[ADDR1]]
+; CHECK-NEXT:    [[GEP2:%.*]] = getelementptr i8, ptr [[PTR]], i64 [[ADDR2_OR_DISJOINT]]
+; CHECK-NEXT:    [[GEP3:%.*]] = getelementptr i8, ptr [[PTR]], i64 [[ADDR3_OR_DISJOINT]]
+; CHECK-NEXT:    [[VAL1:%.*]] = load half, ptr [[GEP1]], align 2
+; CHECK-NEXT:    [[VAL2:%.*]] = load half, ptr [[GEP2]], align 2
+; CHECK-NEXT:    [[VAL3:%.*]] = load half, ptr [[GEP3]], align 2
+; CHECK-NEXT:    ret void
+;
+entry:
+  %base = and i64 %input, -8192    ; Clear low bits
+  %addr1 = xor i64 %base, 32
+  %addr2 = xor i64 %base, 2080
+  %addr3 = xor i64 %base, 4128
+  %gep1 = getelementptr i8, ptr %ptr, i64 %addr1
+  %gep2 = getelementptr i8, ptr %ptr, i64 %addr2
+  %gep3 = getelementptr i8, ptr %ptr, i64 %addr3
+  %val1 = load half, ptr %gep1
+  %val2 = load half, ptr %gep2
+  %val3 = load half, ptr %gep3
+  ret void
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arsenm wrote:

Fix this to not be dead code

https://github.com/llvm/llvm-project/pull/135788