Remove abs, add a couple more tests

Author: dakersnar

llvm/lib/Transforms/Scalar/InferAlignment.cpp

@@ -74,7 +74,7 @@ bool inferAlignment(Function &F, AssumptionCache &AC, DominatorTree &DT) {
     // Derive the base pointer alignment from the load/store alignment
     // and the offset from the base pointer.
     Align BasePointerAlign =
-        commonAlignment(LoadStoreAlign, OffsetFromBase.abs().getLimitedValue());
+        commonAlignment(LoadStoreAlign, OffsetFromBase.getLimitedValue());
 
     auto [It, Inserted] =
         BestBasePointerAligns.try_emplace(PtrOp, BasePointerAlign);
@@ -85,7 +85,7 @@ bool inferAlignment(Function &F, AssumptionCache &AC, DominatorTree &DT) {
       // improved base pointer alignment for future iterations.
       if (It->second > BasePointerAlign) {
         Align BetterLoadStoreAlign =
-            commonAlignment(It->second, OffsetFromBase.abs().getLimitedValue());
+            commonAlignment(It->second, OffsetFromBase.getLimitedValue());
         return BetterLoadStoreAlign;
       }
       It->second = BasePointerAlign;

llvm/test/Transforms/InferAlignment/propagate-from-other-load-stores.ll

@@ -164,3 +164,31 @@ define void @prop_align_negative_offset_2(ptr %v) {
   %loadUnaligned= load float, ptr %v, align 4
   ret void
 }
+
+define void @prop_align_negative_offset_3(ptr %v) {
+; CHECK-LABEL: define void @prop_align_negative_offset_3(
+; CHECK-SAME: ptr [[V:%.*]]) {
+; CHECK-NEXT:    [[LOADALIGNED:%.*]] = load float, ptr [[V]], align 16
+; CHECK-NEXT:    [[GEPNEGATIVE:%.*]] = getelementptr inbounds nuw i8, ptr [[V]], i64 -8
+; CHECK-NEXT:    [[LOADUNALIGNED:%.*]] = load float, ptr [[GEPNEGATIVE]], align 8
+; CHECK-NEXT:    ret void
+;
+  %loadAligned= load float, ptr %v, align 16
+  %gepNegative = getelementptr inbounds nuw i8, ptr %v, i64 -8
+  %loadUnaligned = load float, ptr %gepNegative, align 4
+  ret void
+}
+
+define void @prop_align_negative_offset_4(ptr %v) {
+; CHECK-LABEL: define void @prop_align_negative_offset_4(
+; CHECK-SAME: ptr [[V:%.*]]) {
+; CHECK-NEXT:    [[LOADALIGNED:%.*]] = load float, ptr [[V]], align 16
+; CHECK-NEXT:    [[GEPNEGATIVE:%.*]] = getelementptr inbounds nuw i8, ptr [[V]], i64 -20
+; CHECK-NEXT:    [[LOADUNALIGNED:%.*]] = load float, ptr [[GEPNEGATIVE]], align 4
+; CHECK-NEXT:    ret void
+;
+  %loadAligned= load float, ptr %v, align 16
+  %gepNegative = getelementptr inbounds nuw i8, ptr %v, i64 -20
+  %loadUnaligned = load float, ptr %gepNegative, align 4
+  ret void
+}