[PATCH] D107622: [FuncSpec] Return changed if function is changed by tryToReplaceWithConstant

[Chuanqi Xu via Phabricator via llvm-commits]

ChuanqiXu created this revision.
ChuanqiXu added reviewers: SjoerdMeijer, fhahn.
Herald added subscribers: snehasish, ormris, hiraditya.
ChuanqiXu requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

The may get changed before specialization by RunSCCPSolver. In other words, the pass may change the function without specialization happens. Add test and comment to reveal this. 
And it may return `No Changed` if the function get changed by RunSCCPSolver before the specialization. It looks like a potential bug.

Test Plan: check-all


https://reviews.llvm.org/D107622

Files:
  llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
  llvm/test/Transforms/FunctionSpecialization/function-specialization-constant-expression.ll


Index: llvm/test/Transforms/FunctionSpecialization/function-specialization-constant-expression.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/FunctionSpecialization/function-specialization-constant-expression.ll
@@ -0,0 +1,49 @@
+; Test function specialization wouldn't crash due to constant expression.
+; Note that this test case shows that function specialization pass would
+; transform the function even if no specialization happened.
+; RUN: opt -function-specialization -S < %s | FileCheck %s
+
+; CHECK: plus:
+; CHECK-NEXT:  %{{.*}} = call i64 @func2(i64* getelementptr inbounds (%struct, %struct* @Global, i32 0, i32 3))
+; CHECK: minus:
+; CHECK-NEXT: %{{.*}} = call i64 @func2(i64* getelementptr inbounds (%struct, %struct* @Global, i32 0, i32 4))
+
+%struct = type { i8, i16, i32, i64, i64}
+ at Global = internal constant %struct {i8 0, i16 1, i32 2, i64 3, i64 4}
+define internal i64 @zoo(i1 %flag) {
+entry:
+  br i1 %flag, label %plus, label %minus
+
+plus:
+  %arg = getelementptr %struct, %struct* @Global, i32 0, i32 3
+  %tmp0 = call i64 @func2(i64* %arg)
+  br label %merge
+
+minus:
+  %arg2 = getelementptr %struct, %struct* @Global, i32 0, i32 4
+  %tmp1 = call i64 @func2(i64* %arg2)
+  br label %merge
+
+merge:
+  %tmp2 = phi i64 [ %tmp0, %plus ], [ %tmp1, %minus]
+  ret i64 %tmp2
+}
+
+define internal i64 @func2(i64 *%x) {
+entry:
+  %val = ptrtoint i64* %x to i64
+  ret i64 %val
+}
+
+define internal i64 @func(i64 *%x, i64 (i64*)* %binop) {
+entry:
+  %tmp0 = call i64 %binop(i64* %x)
+  ret i64 %tmp0
+}
+
+define i64 @main() {
+    %1 = call i64 @zoo(i1 0)
+    %2 = call i64 @zoo(i1 1)
+    %3 = add i64 %1, %2
+    ret i64 %3
+}
\ No newline at end of file
Index: llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
===================================================================
--- llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
+++ llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
@@ -26,6 +26,8 @@
 // `func-specialization-max-iters`
 //   increases linearly. See discussion in https://reviews.llvm.org/D106426 for
 //   details.
+// - Don't transform the function if there is no function specialization
+// happens.
 //
 //===----------------------------------------------------------------------===//
 
@@ -760,7 +762,7 @@
         if (!Solver.isBlockExecutable(&BB))
           continue;
         for (auto &I : make_early_inc_range(BB))
-          FS.tryToReplaceWithConstant(&I);
+          Changed |= FS.tryToReplaceWithConstant(&I);
       }
     }
   };


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