llvm-reduce: Do not reduce alloca array sizes to 0 (#132864)

Fixes #64340

Author: arsenm

llvm/test/tools/llvm-reduce/reduce-operands-alloca.ll

@@ -0,0 +1,69 @@
+; RUN: llvm-reduce --abort-on-invalid-reduction --delta-passes=operands-zero --test FileCheck --test-arg --check-prefix=CHECK --test-arg %s --test-arg --input-file %s -o %t
+; RUN: FileCheck %s --check-prefixes=CHECK,ZERO < %t
+
+; RUN: llvm-reduce --abort-on-invalid-reduction --delta-passes=operands-one --test FileCheck --test-arg --check-prefix=CHECK --test-arg %s --test-arg --input-file %s -o %t
+; RUN: FileCheck %s --check-prefixes=CHECK,ONE < %t
+
+; RUN: llvm-reduce --abort-on-invalid-reduction --delta-passes=operands-poison --test FileCheck --test-arg --check-prefix=CHECK --test-arg %s --test-arg --input-file %s -o %t
+; RUN: FileCheck %s --check-prefixes=CHECK,POISON < %t
+
+
+; CHECK-LABEL: @dyn_alloca(
+; ZERO: %alloca = alloca i32, i32 %size, align 4
+; ONE: %alloca = alloca i32, align 4
+; POISON: %alloca = alloca i32, i32 %size, align 4
+define void @dyn_alloca(i32 %size) {
+ %alloca = alloca i32, i32 %size
+ store i32 0, ptr %alloca
+ ret void
+}
+
+; CHECK-LABEL: @alloca_0_elt(
+; ZERO: %alloca = alloca i32, i32 0, align 4
+; ONE: %alloca = alloca i32, i32 0, align 4
+; POISON:  %alloca = alloca i32, i32 0, align 4
+define void @alloca_0_elt() {
+ %alloca = alloca i32, i32 0
+ store i32 0, ptr %alloca
+ ret void
+}
+
+; CHECK-LABEL: @alloca_1_elt(
+; ZERO: %alloca = alloca i32, align 4
+; ONE: %alloca = alloca i32, align 4
+; POISON: %alloca = alloca i32, align 4
+define void @alloca_1_elt() {
+ %alloca = alloca i32, i32 1
+ store i32 0, ptr %alloca
+ ret void
+}
+
+; CHECK-LABEL: @alloca_1024_elt(
+; ZERO: %alloca = alloca i32, i32 1024, align 4
+; ONE: %alloca = alloca i32, align 4
+; POISON: %alloca = alloca i32, i32 1024, align 4
+define void @alloca_1024_elt() {
+ %alloca = alloca i32, i32 1024
+ store i32 0, ptr %alloca
+ ret void
+}
+
+; CHECK-LABEL: @alloca_poison_elt(
+; ZERO: %alloca = alloca i32, i32 poison, align 4
+; ONE: %alloca = alloca i32, align 4
+; POISON: %alloca = alloca i32, i32 poison, align 4
+define void @alloca_poison_elt() {
+ %alloca = alloca i32, i32 poison
+ store i32 0, ptr %alloca
+ ret void
+}
+
+; CHECK-LABEL: @alloca_constexpr_elt(
+; ZERO: %alloca = alloca i32, i32 ptrtoint (ptr @alloca_constexpr_elt to i32)
+; ONE: %alloca = alloca i32, align 4
+; POISON: %alloca = alloca i32, i32 ptrtoint (ptr @alloca_constexpr_elt to i32)
+define void @alloca_constexpr_elt() {
+ %alloca = alloca i32, i32 ptrtoint (ptr @alloca_constexpr_elt to i32)
+ store i32 0, ptr %alloca
+ ret void
+}

llvm/tools/llvm-reduce/deltas/ReduceOperands.cpp

@@ -125,6 +125,11 @@ void llvm::reduceOperandsZeroDeltaPass(Oracle &O, ReducerWorkItem &WorkItem) {
   auto ReduceValue = [](Use &Op) -> Value * {
     if (!shouldReduceOperand(Op))
       return nullptr;
+
+    // Avoid introducing 0-sized allocations.
+    if (isa<AllocaInst>(Op.getUser()))
+      return nullptr;
+
     // Don't duplicate an existing switch case.
     if (auto *IntTy = dyn_cast<IntegerType>(Op->getType()))
       if (switchCaseExists(Op, ConstantInt::get(IntTy, 0)))