https://github.com/arsenm created
https://github.com/llvm/llvm-project/pull/134794
Use splitBasicBlock and avoid directly dealing with the specific of
how to trim the existing terminators. We just need to deal with
unconditional branch to return.
>From c1e5029de5918b2317f6d01517e5f2d50cf676ad Mon Sep 17 00:00:00 2001
From: Matt Arsenault <matthew.arsena...@amd.com>
Date: Tue, 8 Apr 2025 11:16:01 +0700
Subject: [PATCH] llvm-reduce: Support exotic terminators in
instructions-to-return
Use splitBasicBlock and avoid directly dealing with the specific of
how to trim the existing terminators. We just need to deal with
unconditional branch to return.
---
.../reduce-values-to-return-callbr.ll | 54 ++++++++++++++++++
.../reduce-values-to-return-invoke.ll | 56 +++++++++++++++++++
.../deltas/ReduceValuesToReturn.cpp | 50 ++++-------------
llvm/tools/llvm-reduce/deltas/Utils.cpp | 2 +-
4 files changed, 122 insertions(+), 40 deletions(-)
create mode 100644
llvm/test/tools/llvm-reduce/reduce-values-to-return-callbr.ll
create mode 100644
llvm/test/tools/llvm-reduce/reduce-values-to-return-invoke.ll
diff --git a/llvm/test/tools/llvm-reduce/reduce-values-to-return-callbr.ll
b/llvm/test/tools/llvm-reduce/reduce-values-to-return-callbr.ll
new file mode 100644
index 0000000000000..da2f225f0405b
--- /dev/null
+++ b/llvm/test/tools/llvm-reduce/reduce-values-to-return-callbr.ll
@@ -0,0 +1,54 @@
+; RUN: llvm-reduce --abort-on-invalid-reduction
--delta-passes=instructions-to-return --test FileCheck --test-arg
--check-prefix=INTERESTING --test-arg %s --test-arg --input-file %s -o %t
+; RUN: FileCheck --check-prefix=RESULT %s < %t
+
+@gv = global i32 0, align 4
+
+; INTERESTING-LABEL: @callbr0(
+; INTERESTING: %load0 = load i32, ptr %arg0
+; INTERESTING: store i32 %load0, ptr @gv
+
+; RESULT-LABEL: define void @callbr0(ptr %arg0) {
+; RESULT: %load0 = load i32, ptr %arg0, align 4
+; RESULT-NEXT: %callbr = callbr i32 asm
+define void @callbr0(ptr %arg0) {
+entry:
+ %load0 = load i32, ptr %arg0
+ %callbr = callbr i32 asm "", "=r,r,!i,!i"(i32 %load0)
+ to label %one [label %two, label %three]
+one:
+ store i32 %load0, ptr @gv
+ ret void
+
+two:
+ store i32 %load0, ptr @gv
+ ret void
+
+three:
+ store i32 %load0, ptr @gv
+ ret void
+}
+
+; INTERESTING-LABEL: @callbr1(
+; INTERESTING: %load0 = load i32, ptr %arg0
+
+; RESULT-LABEL: define i32 @callbr1(ptr %arg0) {
+; RESULT-NEXT: entry:
+; RESULT-NEXT: %load0 = load i32, ptr %arg0
+; RESULT-NEXT: ret i32 %load0
+define void @callbr1(ptr %arg0) {
+entry:
+ %load0 = load i32, ptr %arg0
+ %callbr = callbr i32 asm "", "=r,r,!i,!i"(i32 %load0)
+ to label %one [label %two, label %three]
+one:
+ store i32 %load0, ptr @gv
+ ret void
+
+two:
+ store i32 %load0, ptr @gv
+ ret void
+
+three:
+ store i32 %load0, ptr @gv
+ ret void
+}
diff --git a/llvm/test/tools/llvm-reduce/reduce-values-to-return-invoke.ll
b/llvm/test/tools/llvm-reduce/reduce-values-to-return-invoke.ll
new file mode 100644
index 0000000000000..efa1e5377160e
--- /dev/null
+++ b/llvm/test/tools/llvm-reduce/reduce-values-to-return-invoke.ll
@@ -0,0 +1,56 @@
+; RUN: llvm-reduce --abort-on-invalid-reduction
--delta-passes=instructions-to-return --test FileCheck --test-arg
--check-prefix=INTERESTING --test-arg %s --test-arg --input-file %s -o %t
+; RUN: FileCheck --check-prefix=RESULT %s < %t
+
+@gv = global i32 0, align 4
+
+
+define i32 @has_invoke_user(ptr %arg) {
+ %load = load i32, ptr %arg
+ store i32 %load, ptr @gv
+ ret i32 9
+}
+
+declare i32 @__gxx_personality_v0(...)
+
+; INTERESTING-LABEL: @invoker_keep_invoke(
+; INTERESTING: %invoke
+; RESULT: %invoke = invoke i32 @has_invoke_user(ptr %arg)
+define void @invoker_keep_invoke(ptr %arg) personality ptr
@__gxx_personality_v0 {
+bb:
+ %invoke = invoke i32 @has_invoke_user(ptr %arg)
+ to label %bb3 unwind label %bb1
+
+bb1:
+ landingpad { ptr, i32 }
+ catch ptr null
+ ret void
+
+bb3:
+ store i32 %invoke, ptr null
+ ret void
+}
+
+; INTERESTING-LABEL: @invoker_drop_invoke(
+; INTERESTING: %add = add i32
+
+; RESULT-LABEL: define i32 @invoker_drop_invoke(i32 %arg0, ptr %arg1)
personality ptr @__gxx_personality_v0 {
+; RESULT-NEXT: bb:
+; RESULT-NEXT: %add = add i32 %arg0, 9
+; RESULT-NEXT: ret i32 %add
+; RESULT-NEXT: }
+define void @invoker_drop_invoke(i32 %arg0, ptr %arg1) personality ptr
@__gxx_personality_v0 {
+bb:
+ %add = add i32 %arg0, 9
+ %invoke = invoke i32 @has_invoke_user(ptr %arg1)
+ to label %bb3 unwind label %bb1
+
+bb1:
+ landingpad { ptr, i32 }
+ catch ptr null
+ br label %bb3
+
+bb3:
+ %phi = phi i32 [ %invoke, %bb ], [ %add, %bb1 ]
+ store i32 %phi, ptr null
+ ret void
+}
diff --git a/llvm/tools/llvm-reduce/deltas/ReduceValuesToReturn.cpp
b/llvm/tools/llvm-reduce/deltas/ReduceValuesToReturn.cpp
index 72cfa830579a2..d2adce8381044 100644
--- a/llvm/tools/llvm-reduce/deltas/ReduceValuesToReturn.cpp
+++ b/llvm/tools/llvm-reduce/deltas/ReduceValuesToReturn.cpp
@@ -22,7 +22,6 @@
#include "llvm/IR/Attributes.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Instructions.h"
-#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
using namespace llvm;
@@ -55,7 +54,7 @@ static void rewriteFuncWithReturnType(Function &OldF, Value
*NewRetValue) {
BasicBlock *NewRetBlock = NewRetI ? NewRetI->getParent() : &EntryBB;
BasicBlock::iterator NewValIt =
- NewRetI ? NewRetI->getIterator() : EntryBB.end();
+ NewRetI ? std::next(NewRetI->getIterator()) : EntryBB.begin();
Type *OldRetTy = OldFuncTy->getReturnType();
@@ -73,28 +72,16 @@ static void rewriteFuncWithReturnType(Function &OldF, Value
*NewRetValue) {
}
}
- // Now prune any CFG edges we have to deal with.
- //
- // Use KeepOneInputPHIs in case the instruction we are using for the return
is
- // that phi.
- // TODO: Could avoid this with fancier iterator management.
- for (BasicBlock *Succ : successors(NewRetBlock))
- Succ->removePredecessor(NewRetBlock, /*KeepOneInputPHIs=*/true);
-
- // Now delete the tail of this block, in reverse to delete uses before defs.
- for (Instruction &I : make_early_inc_range(
- make_range(NewRetBlock->rbegin(), NewValIt.getReverse()))) {
- Value *Replacement = getDefaultValue(I.getType());
- I.replaceAllUsesWith(Replacement);
- I.eraseFromParent();
- }
+ // If we're returning an instruction, split the basic block so we can let
+ // EliminateUnreachableBlocks cleanup the successors.
+ BasicBlock *TailBB = NewRetBlock->splitBasicBlock(NewValIt);
+ // Replace the unconditional branch splitBasicBlock created
+ NewRetBlock->getTerminator()->eraseFromParent();
ReturnInst::Create(Ctx, NewRetValue, NewRetBlock);
- // TODO: We may be eliminating blocks that were originally unreachable. We
- // probably ought to only be pruning blocks that became dead directly as a
- // result of our pruning here.
- EliminateUnreachableBlocks(OldF);
+ // Now prune any CFG edges we have to deal with.
+ simpleSimplifyCFG(OldF, {TailBB}, /*FoldBlockIntoPredecessor=*/false);
// Drop the incompatible attributes before we copy over to the new function.
if (OldRetTy != NewRetTy) {
@@ -199,20 +186,6 @@ static bool shouldReplaceNonVoidReturnValue(const
BasicBlock &BB,
return true;
}
-static bool canHandleSuccessors(const BasicBlock &BB) {
- // TODO: Handle invoke and other exotic terminators
- if (!isa<ReturnInst, UnreachableInst, BranchInst, SwitchInst>(
- BB.getTerminator()))
- return false;
-
- for (const BasicBlock *Succ : successors(&BB)) {
- if (!Succ->canSplitPredecessors())
- return false;
- }
-
- return true;
-}
-
static bool shouldForwardValueToReturn(const BasicBlock &BB, const Value *V,
Type *RetTy) {
if (!isReallyValidReturnType(V->getType()))
@@ -231,10 +204,9 @@ static bool tryForwardingInstructionsToReturn(
Type *RetTy = F.getReturnType();
for (BasicBlock &BB : F) {
- if (!canHandleSuccessors(BB))
- continue;
-
- for (Instruction &I : BB) {
+ // Skip the terminator, we can't insert a second terminator to return its
+ // value.
+ for (Instruction &I : make_range(BB.begin(), std::prev(BB.end()))) {
if (shouldForwardValueToReturn(BB, &I, RetTy) && !O.shouldKeep()) {
FuncsToReplace.emplace_back(&F, &I);
return true;
diff --git a/llvm/tools/llvm-reduce/deltas/Utils.cpp
b/llvm/tools/llvm-reduce/deltas/Utils.cpp
index a980a0f9fad2f..e2ebeb5eefc3c 100644
--- a/llvm/tools/llvm-reduce/deltas/Utils.cpp
+++ b/llvm/tools/llvm-reduce/deltas/Utils.cpp
@@ -79,7 +79,7 @@ void llvm::simpleSimplifyCFG(Function &F, ArrayRef<BasicBlock
*> BBs,
for (BasicBlock *BB : Unreachable) {
for (BasicBlock *Successor : successors(&*BB))
if (Visited.count(Successor))
- Successor->removePredecessor(&*BB);
+ Successor->removePredecessor(&*BB, /*KeepOneInputPHIs=*/true);
BB->dropAllReferences();
}
_______________________________________________
llvm-branch-commits mailing list
llvm-branch-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
