================
@@ -308,3 +308,70 @@ TEST(SSAUpdaterBulk, TwoBBLoop) {
EXPECT_EQ(Phi->getIncomingValueForBlock(Entry), ConstantInt::get(I32Ty, 0));
EXPECT_EQ(Phi->getIncomingValueForBlock(Loop), I);
}
+
+TEST(SSAUpdaterBulk, SimplifyPHIs) {
+ const char *IR = R"(
+ define void @main(i32 %val, i1 %cond) {
+ entry:
+ br i1 %cond, label %left, label %right
+ left:
+ %add = add i32 %val, 1
+ br label %exit
+ right:
+ %sub = sub i32 %val, 1
+ br label %exit
+ exit:
+ %phi = phi i32 [ %sub, %right ], [ %add, %left ]
+ %cmp = icmp slt i32 0, 42
+ ret void
+ }
+ )";
+
+ llvm::LLVMContext Context;
+ llvm::SMDiagnostic Err;
+ std::unique_ptr<llvm::Module> M = llvm::parseAssemblyString(IR, Err,
Context);
+ ASSERT_NE(M, nullptr) << "Failed to parse IR: " << Err.getMessage();
+
+ Function *F = M->getFunction("main");
+ auto *Entry = &F->getEntryBlock();
+ auto *Left = Entry->getTerminator()->getSuccessor(0);
+ auto *Right = Entry->getTerminator()->getSuccessor(1);
+ auto *Exit = Left->getSingleSuccessor();
+ auto *Val = &*F->arg_begin();
+ auto *Phi = &Exit->front();
+ auto *Cmp = &*std::next(Exit->begin());
+ auto *Add = &Left->front();
+ auto *Sub = &Right->front();
+
+ SSAUpdaterBulk Updater;
+ Type *I32Ty = Type::getInt32Ty(Context);
+
+ // Use %val directly instead of creating a phi.
+ unsigned ValVar = Updater.AddVariable("Val", I32Ty);
+ Updater.AddAvailableValue(ValVar, Left, Val);
+ Updater.AddAvailableValue(ValVar, Right, Val);
+ Updater.AddUse(ValVar, &Cmp->getOperandUse(0));
+
+ // Use existing %phi for %add and %sub values.
+ unsigned AddSubVar = Updater.AddVariable("AddSub", I32Ty);
+ Updater.AddAvailableValue(AddSubVar, Left, Add);
+ Updater.AddAvailableValue(AddSubVar, Right, Sub);
+ Updater.AddUse(AddSubVar, &Cmp->getOperandUse(1));
+
+ auto ExitSizeBefore = Exit->size();
+ DominatorTree DT(*F);
+ Updater.RewriteAndOptimizeAllUses(DT);
+
+#if 0 // Enable for debugging.
+ Exit->dump();
+ // Output:
+ // exit: ; preds = %right, %left
+ // %phi = phi i32 [ %sub, %right ], [ %add, %left ]
+ // %cmp = icmp slt i32 %val, %phi
+ // ret void
+#endif
----------------
arsenm wrote:
```suggestion
// Output:
// exit: ; preds = %right, %left
// %phi = phi i32 [ %sub, %right ], [ %add, %left ]
// %cmp = icmp slt i32 %val, %phi
// ret void
```
Don't leave the disabled code
https://github.com/llvm/llvm-project/pull/135180
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