Value-number GVNHoist loads by result type as well as pointer address.

Avoids merge errors when opaque pointers are loaded into different types. Reviewed by: jcranmer-intel, hiraditya Differential Revision: https://reviews.llvm.org/D122521
llvm · Mar 30, 2022 · c28ce74 · c28ce74
1 parent 85eae45
commit c28ce74
Show file tree

Hide file tree

Showing 2 changed files with 124 additions and 3 deletions.
diff --git a/llvm/lib/Transforms/Scalar/GVNHoist.cpp b/llvm/lib/Transforms/Scalar/GVNHoist.cpp
@@ -124,7 +124,7 @@ using HoistingPointInfo = std::pair<BasicBlock *, SmallVecInsn>;
 using HoistingPointList = SmallVector<HoistingPointInfo, 4>;
 
 // A map from a pair of VNs to all the instructions with those VNs.
-using VNType = std::pair<unsigned, unsigned>;
+using VNType = std::pair<unsigned, uintptr_t>;
 
 using VNtoInsns = DenseMap<VNType, SmallVector<Instruction *, 4>>;
 
@@ -159,7 +159,7 @@ using InValuesType =
 
 // An invalid value number Used when inserting a single value number into
 // VNtoInsns.
-enum : unsigned { InvalidVN = ~2U };
+enum : uintptr_t { InvalidVN = ~(uintptr_t)2 };
 
 // Records all scalar instructions candidate for code hoisting.
 class InsnInfo {
@@ -185,7 +185,9 @@ class LoadInfo {
   void insert(LoadInst *Load, GVNPass::ValueTable &VN) {
     if (Load->isSimple()) {
       unsigned V = VN.lookupOrAdd(Load->getPointerOperand());
-      VNtoLoads[{V, InvalidVN}].push_back(Load);
+      // With opaque pointers we may have loads from the same pointer with
+      // different result types, which should be disambiguated.
+      VNtoLoads[{V, (uintptr_t)Load->getType()}].push_back(Load);
     }
   }
 

diff --git a/llvm/test/Transforms/GVNHoist/opaque-diff-type.ll b/llvm/test/Transforms/GVNHoist/opaque-diff-type.ll
@@ -0,0 +1,119 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -opaque-pointers -passes="gvn-hoist" -S %s | FileCheck %s
+
+; Checks that gvn-hoist does not try to merge loads of the same source pointer
+; when the results are different types.
+
+define linkonce_odr void @i16i32(ptr %arg) {
+; CHECK-LABEL: @i16i32(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    br i1 false, label [[BB1:%.*]], label [[BB2:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[T:%.*]] = load i16, ptr [[ARG:%.*]], align 4
+; CHECK-NEXT:    br label [[BB2]]
+; CHECK:       bb2:
+; CHECK-NEXT:    [[T3:%.*]] = load i32, ptr [[ARG]], align 8
+; CHECK-NEXT:    ret void
+;
+bb:
+  br i1 false, label %bb1, label %bb2
+
+bb1:                                              ; preds = %bb
+  %t = load i16, ptr %arg, align 4
+  br label %bb2
+
+bb2:                                              ; preds = %bb1, %bb
+  %t3 = load i32, ptr %arg, align 8
+  ret void
+}
+
+define linkonce_odr void @i32f32(ptr %arg) {
+; CHECK-LABEL: @i32f32(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    br i1 false, label [[BB1:%.*]], label [[BB2:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[T:%.*]] = load i32, ptr [[ARG:%.*]], align 4
+; CHECK-NEXT:    br label [[BB2]]
+; CHECK:       bb2:
+; CHECK-NEXT:    [[T3:%.*]] = load float, ptr [[ARG]], align 8
+; CHECK-NEXT:    ret void
+;
+bb:
+  br i1 false, label %bb1, label %bb2
+
+bb1:                                              ; preds = %bb
+  %t = load i32, ptr %arg, align 4
+  br label %bb2
+
+bb2:                                              ; preds = %bb1, %bb
+  %t3 = load float, ptr %arg, align 8
+  ret void
+}
+
+define linkonce_odr void @i64ptr(ptr %arg) {
+; CHECK-LABEL: @i64ptr(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    br i1 false, label [[BB1:%.*]], label [[BB2:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[T:%.*]] = load i64, ptr [[ARG:%.*]], align 4
+; CHECK-NEXT:    br label [[BB2]]
+; CHECK:       bb2:
+; CHECK-NEXT:    [[T3:%.*]] = load ptr, ptr [[ARG]], align 8
+; CHECK-NEXT:    ret void
+;
+bb:
+  br i1 false, label %bb1, label %bb2
+
+bb1:                                              ; preds = %bb
+  %t = load i64, ptr %arg, align 4
+  br label %bb2
+
+bb2:                                              ; preds = %bb1, %bb
+  %t3 = load ptr, ptr %arg, align 8
+  ret void
+}
+
+define linkonce_odr void @ptrptr_diff_aspace(ptr %arg) {
+; CHECK-LABEL: @ptrptr_diff_aspace(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    br i1 false, label [[BB1:%.*]], label [[BB2:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[T:%.*]] = load ptr addrspace(4), ptr [[ARG:%.*]], align 4
+; CHECK-NEXT:    br label [[BB2]]
+; CHECK:       bb2:
+; CHECK-NEXT:    [[T3:%.*]] = load ptr addrspace(2), ptr [[ARG]], align 8
+; CHECK-NEXT:    ret void
+;
+bb:
+  br i1 false, label %bb1, label %bb2
+
+bb1:                                              ; preds = %bb
+  %t = load ptr addrspace(4), ptr %arg, align 4
+  br label %bb2
+
+bb2:                                              ; preds = %bb1, %bb
+  %t3 = load ptr addrspace(2), ptr %arg, align 8
+  ret void
+}
+
+define linkonce_odr void @ptrptr(ptr %arg) {
+; CHECK-LABEL: @ptrptr(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    [[T3:%.*]] = load ptr, ptr [[ARG:%.*]], align 4
+; CHECK-NEXT:    br i1 false, label [[BB1:%.*]], label [[BB2:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    br label [[BB2]]
+; CHECK:       bb2:
+; CHECK-NEXT:    ret void
+;
+bb:
+  br i1 false, label %bb1, label %bb2
+
+bb1:                                              ; preds = %bb
+  %t = load ptr, ptr %arg, align 4
+  br label %bb2
+
+bb2:                                              ; preds = %bb1, %bb
+  %t3 = load ptr, ptr %arg, align 8
+  ret void
+}