[SCCP] Check whether the default case is reachable #76295
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
@llvm/pr-subscribers-function-specialization Author: Yingwei Zheng (dtcxzyw) ChangesThis patch eliminates unreachable default cases using range information. Full diff: https://github.com/llvm/llvm-project/pull/76295.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/Utils/SCCPSolver.cpp b/llvm/lib/Transforms/Utils/SCCPSolver.cpp
index ab95698abc4399..3dc6016a0a373f 100644
--- a/llvm/lib/Transforms/Utils/SCCPSolver.cpp
+++ b/llvm/lib/Transforms/Utils/SCCPSolver.cpp
@@ -310,6 +310,7 @@ bool SCCPSolver::removeNonFeasibleEdges(BasicBlock *BB, DomTreeUpdater &DTU,
new UnreachableInst(DefaultDest->getContext(), NewUnreachableBB);
}
+ DefaultDest->removePredecessor(BB);
SI->setDefaultDest(NewUnreachableBB);
Updates.push_back({DominatorTree::Delete, BB, DefaultDest});
Updates.push_back({DominatorTree::Insert, BB, NewUnreachableBB});
@@ -1063,14 +1064,17 @@ void SCCPInstVisitor::getFeasibleSuccessors(Instruction &TI,
// is ready.
if (SCValue.isConstantRange(/*UndefAllowed=*/false)) {
const ConstantRange &Range = SCValue.getConstantRange();
+ unsigned ReachableCaseCount = 0;
for (const auto &Case : SI->cases()) {
const APInt &CaseValue = Case.getCaseValue()->getValue();
- if (Range.contains(CaseValue))
+ if (Range.contains(CaseValue)) {
Succs[Case.getSuccessorIndex()] = true;
+ ++ReachableCaseCount;
+ }
}
- // TODO: Determine whether default case is reachable.
- Succs[SI->case_default()->getSuccessorIndex()] = true;
+ Succs[SI->case_default()->getSuccessorIndex()] =
+ Range.isSizeLargerThan(ReachableCaseCount);
return;
}
diff --git a/llvm/test/Transforms/SCCP/switch.ll b/llvm/test/Transforms/SCCP/switch.ll
index 19e72217fd03bf..306f0eebf2b408 100644
--- a/llvm/test/Transforms/SCCP/switch.ll
+++ b/llvm/test/Transforms/SCCP/switch.ll
@@ -4,6 +4,8 @@
; Make sure we always consider the default edge executable for a switch
; with no cases.
declare void @foo()
+declare i32 @g(i32)
+
define void @test1() {
; CHECK-LABEL: @test1(
; CHECK-NEXT: switch i32 undef, label [[D:%.*]] [
@@ -115,17 +117,16 @@ switch.1:
ret i32 %phi
}
-; TODO: Determine that the default destination is dead.
define i32 @test_local_range(ptr %p) {
; CHECK-LABEL: @test_local_range(
; CHECK-NEXT: [[X:%.*]] = load i32, ptr [[P:%.*]], align 4, !range [[RNG0]]
-; CHECK-NEXT: switch i32 [[X]], label [[SWITCH_DEFAULT:%.*]] [
+; CHECK-NEXT: switch i32 [[X]], label [[DEFAULT_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 0, label [[SWITCH_0:%.*]]
; CHECK-NEXT: i32 1, label [[SWITCH_1:%.*]]
; CHECK-NEXT: i32 2, label [[SWITCH_2:%.*]]
; CHECK-NEXT: ]
-; CHECK: switch.default:
-; CHECK-NEXT: ret i32 -1
+; CHECK: default.unreachable:
+; CHECK-NEXT: unreachable
; CHECK: switch.0:
; CHECK-NEXT: ret i32 0
; CHECK: switch.1:
@@ -161,14 +162,14 @@ switch.3:
define i32 @test_duplicate_successors(ptr %p) {
; CHECK-LABEL: @test_duplicate_successors(
; CHECK-NEXT: [[X:%.*]] = load i32, ptr [[P:%.*]], align 4, !range [[RNG0]]
-; CHECK-NEXT: switch i32 [[X]], label [[SWITCH_DEFAULT:%.*]] [
+; CHECK-NEXT: switch i32 [[X]], label [[DEFAULT_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 0, label [[SWITCH_0:%.*]]
; CHECK-NEXT: i32 1, label [[SWITCH_0]]
; CHECK-NEXT: i32 2, label [[SWITCH_1:%.*]]
; CHECK-NEXT: i32 3, label [[SWITCH_1]]
; CHECK-NEXT: ]
-; CHECK: switch.default:
-; CHECK-NEXT: ret i32 -1
+; CHECK: default.unreachable:
+; CHECK-NEXT: unreachable
; CHECK: switch.0:
; CHECK-NEXT: ret i32 0
; CHECK: switch.1:
@@ -201,13 +202,13 @@ switch.2:
; range information.
define internal i32 @test_ip_range(i32 %x) {
; CHECK-LABEL: @test_ip_range(
-; CHECK-NEXT: switch i32 [[X:%.*]], label [[SWITCH_DEFAULT:%.*]] [
+; CHECK-NEXT: switch i32 [[X:%.*]], label [[DEFAULT_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 3, label [[SWITCH_3:%.*]]
; CHECK-NEXT: i32 1, label [[SWITCH_1:%.*]]
; CHECK-NEXT: i32 2, label [[SWITCH_2:%.*]]
; CHECK-NEXT: ], !prof [[PROF1:![0-9]+]]
-; CHECK: switch.default:
-; CHECK-NEXT: ret i32 -1
+; CHECK: default.unreachable:
+; CHECK-NEXT: unreachable
; CHECK: switch.1:
; CHECK-NEXT: ret i32 1
; CHECK: switch.2:
@@ -240,8 +241,8 @@ switch.3:
define void @call_test_ip_range() {
; CHECK-LABEL: @call_test_ip_range(
-; CHECK-NEXT: [[TMP1:%.*]] = call i32 @test_ip_range(i32 1)
-; CHECK-NEXT: [[TMP2:%.*]] = call i32 @test_ip_range(i32 3)
+; CHECK-NEXT: [[TMP1:%.*]] = call i32 @test_ip_range(i32 1), !range [[RNG2:![0-9]+]]
+; CHECK-NEXT: [[TMP2:%.*]] = call i32 @test_ip_range(i32 3), !range [[RNG2]]
; CHECK-NEXT: ret void
;
call i32 @test_ip_range(i32 1)
@@ -301,6 +302,72 @@ end.2:
ret i32 20
}
+define i32 @test_default_unreachable_by_dom_cond(i32 %x) {
+; CHECK-LABEL: @test_default_unreachable_by_dom_cond(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[OR_COND:%.*]] = icmp ult i32 [[X:%.*]], 4
+; CHECK-NEXT: br i1 [[OR_COND]], label [[IF_THEN:%.*]], label [[RETURN:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: switch i32 [[X]], label [[DEFAULT_UNREACHABLE:%.*]] [
+; CHECK-NEXT: i32 0, label [[SW_BB:%.*]]
+; CHECK-NEXT: i32 1, label [[SW_BB2:%.*]]
+; CHECK-NEXT: i32 2, label [[SW_BB4:%.*]]
+; CHECK-NEXT: i32 3, label [[SW_BB6:%.*]]
+; CHECK-NEXT: ]
+; CHECK: sw.bb:
+; CHECK-NEXT: [[CALL:%.*]] = tail call i32 @g(i32 2)
+; CHECK-NEXT: br label [[RETURN]]
+; CHECK: sw.bb2:
+; CHECK-NEXT: [[CALL3:%.*]] = tail call i32 @g(i32 3)
+; CHECK-NEXT: br label [[RETURN]]
+; CHECK: sw.bb4:
+; CHECK-NEXT: [[CALL5:%.*]] = tail call i32 @g(i32 4)
+; CHECK-NEXT: br label [[RETURN]]
+; CHECK: sw.bb6:
+; CHECK-NEXT: [[CALL7:%.*]] = tail call i32 @g(i32 5)
+; CHECK-NEXT: br label [[RETURN]]
+; CHECK: default.unreachable:
+; CHECK-NEXT: unreachable
+; CHECK: return:
+; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i32 [ [[CALL7]], [[SW_BB6]] ], [ [[CALL5]], [[SW_BB4]] ], [ [[CALL3]], [[SW_BB2]] ], [ [[CALL]], [[SW_BB]] ], [ -23, [[ENTRY:%.*]] ]
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+entry:
+ %or.cond = icmp ult i32 %x, 4
+ br i1 %or.cond, label %if.then, label %return
+
+if.then:
+ switch i32 %x, label %sw.epilog [
+ i32 0, label %sw.bb
+ i32 1, label %sw.bb2
+ i32 2, label %sw.bb4
+ i32 3, label %sw.bb6
+ ]
+
+sw.bb:
+ %call = tail call i32 @g(i32 2)
+ br label %return
+
+sw.bb2:
+ %call3 = tail call i32 @g(i32 3)
+ br label %return
+
+sw.bb4:
+ %call5 = tail call i32 @g(i32 4)
+ br label %return
+
+sw.bb6:
+ %call7 = tail call i32 @g(i32 5)
+ br label %return
+
+sw.epilog:
+ call void @foo()
+ br label %return
+
+return:
+ %retval.0 = phi i32 [ %call7, %sw.bb6 ], [ %call5, %sw.bb4 ], [ %call3, %sw.bb2 ], [ %call, %sw.bb ], [ -23, %sw.epilog ], [ -23, %entry ]
+ ret i32 %retval.0
+}
declare void @llvm.assume(i1)
|
|
@llvm/pr-subscribers-llvm-transforms Author: Yingwei Zheng (dtcxzyw) ChangesThis patch eliminates unreachable default cases using range information. Full diff: https://github.com/llvm/llvm-project/pull/76295.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/Utils/SCCPSolver.cpp b/llvm/lib/Transforms/Utils/SCCPSolver.cpp
index ab95698abc4399..3dc6016a0a373f 100644
--- a/llvm/lib/Transforms/Utils/SCCPSolver.cpp
+++ b/llvm/lib/Transforms/Utils/SCCPSolver.cpp
@@ -310,6 +310,7 @@ bool SCCPSolver::removeNonFeasibleEdges(BasicBlock *BB, DomTreeUpdater &DTU,
new UnreachableInst(DefaultDest->getContext(), NewUnreachableBB);
}
+ DefaultDest->removePredecessor(BB);
SI->setDefaultDest(NewUnreachableBB);
Updates.push_back({DominatorTree::Delete, BB, DefaultDest});
Updates.push_back({DominatorTree::Insert, BB, NewUnreachableBB});
@@ -1063,14 +1064,17 @@ void SCCPInstVisitor::getFeasibleSuccessors(Instruction &TI,
// is ready.
if (SCValue.isConstantRange(/*UndefAllowed=*/false)) {
const ConstantRange &Range = SCValue.getConstantRange();
+ unsigned ReachableCaseCount = 0;
for (const auto &Case : SI->cases()) {
const APInt &CaseValue = Case.getCaseValue()->getValue();
- if (Range.contains(CaseValue))
+ if (Range.contains(CaseValue)) {
Succs[Case.getSuccessorIndex()] = true;
+ ++ReachableCaseCount;
+ }
}
- // TODO: Determine whether default case is reachable.
- Succs[SI->case_default()->getSuccessorIndex()] = true;
+ Succs[SI->case_default()->getSuccessorIndex()] =
+ Range.isSizeLargerThan(ReachableCaseCount);
return;
}
diff --git a/llvm/test/Transforms/SCCP/switch.ll b/llvm/test/Transforms/SCCP/switch.ll
index 19e72217fd03bf..306f0eebf2b408 100644
--- a/llvm/test/Transforms/SCCP/switch.ll
+++ b/llvm/test/Transforms/SCCP/switch.ll
@@ -4,6 +4,8 @@
; Make sure we always consider the default edge executable for a switch
; with no cases.
declare void @foo()
+declare i32 @g(i32)
+
define void @test1() {
; CHECK-LABEL: @test1(
; CHECK-NEXT: switch i32 undef, label [[D:%.*]] [
@@ -115,17 +117,16 @@ switch.1:
ret i32 %phi
}
-; TODO: Determine that the default destination is dead.
define i32 @test_local_range(ptr %p) {
; CHECK-LABEL: @test_local_range(
; CHECK-NEXT: [[X:%.*]] = load i32, ptr [[P:%.*]], align 4, !range [[RNG0]]
-; CHECK-NEXT: switch i32 [[X]], label [[SWITCH_DEFAULT:%.*]] [
+; CHECK-NEXT: switch i32 [[X]], label [[DEFAULT_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 0, label [[SWITCH_0:%.*]]
; CHECK-NEXT: i32 1, label [[SWITCH_1:%.*]]
; CHECK-NEXT: i32 2, label [[SWITCH_2:%.*]]
; CHECK-NEXT: ]
-; CHECK: switch.default:
-; CHECK-NEXT: ret i32 -1
+; CHECK: default.unreachable:
+; CHECK-NEXT: unreachable
; CHECK: switch.0:
; CHECK-NEXT: ret i32 0
; CHECK: switch.1:
@@ -161,14 +162,14 @@ switch.3:
define i32 @test_duplicate_successors(ptr %p) {
; CHECK-LABEL: @test_duplicate_successors(
; CHECK-NEXT: [[X:%.*]] = load i32, ptr [[P:%.*]], align 4, !range [[RNG0]]
-; CHECK-NEXT: switch i32 [[X]], label [[SWITCH_DEFAULT:%.*]] [
+; CHECK-NEXT: switch i32 [[X]], label [[DEFAULT_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 0, label [[SWITCH_0:%.*]]
; CHECK-NEXT: i32 1, label [[SWITCH_0]]
; CHECK-NEXT: i32 2, label [[SWITCH_1:%.*]]
; CHECK-NEXT: i32 3, label [[SWITCH_1]]
; CHECK-NEXT: ]
-; CHECK: switch.default:
-; CHECK-NEXT: ret i32 -1
+; CHECK: default.unreachable:
+; CHECK-NEXT: unreachable
; CHECK: switch.0:
; CHECK-NEXT: ret i32 0
; CHECK: switch.1:
@@ -201,13 +202,13 @@ switch.2:
; range information.
define internal i32 @test_ip_range(i32 %x) {
; CHECK-LABEL: @test_ip_range(
-; CHECK-NEXT: switch i32 [[X:%.*]], label [[SWITCH_DEFAULT:%.*]] [
+; CHECK-NEXT: switch i32 [[X:%.*]], label [[DEFAULT_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 3, label [[SWITCH_3:%.*]]
; CHECK-NEXT: i32 1, label [[SWITCH_1:%.*]]
; CHECK-NEXT: i32 2, label [[SWITCH_2:%.*]]
; CHECK-NEXT: ], !prof [[PROF1:![0-9]+]]
-; CHECK: switch.default:
-; CHECK-NEXT: ret i32 -1
+; CHECK: default.unreachable:
+; CHECK-NEXT: unreachable
; CHECK: switch.1:
; CHECK-NEXT: ret i32 1
; CHECK: switch.2:
@@ -240,8 +241,8 @@ switch.3:
define void @call_test_ip_range() {
; CHECK-LABEL: @call_test_ip_range(
-; CHECK-NEXT: [[TMP1:%.*]] = call i32 @test_ip_range(i32 1)
-; CHECK-NEXT: [[TMP2:%.*]] = call i32 @test_ip_range(i32 3)
+; CHECK-NEXT: [[TMP1:%.*]] = call i32 @test_ip_range(i32 1), !range [[RNG2:![0-9]+]]
+; CHECK-NEXT: [[TMP2:%.*]] = call i32 @test_ip_range(i32 3), !range [[RNG2]]
; CHECK-NEXT: ret void
;
call i32 @test_ip_range(i32 1)
@@ -301,6 +302,72 @@ end.2:
ret i32 20
}
+define i32 @test_default_unreachable_by_dom_cond(i32 %x) {
+; CHECK-LABEL: @test_default_unreachable_by_dom_cond(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[OR_COND:%.*]] = icmp ult i32 [[X:%.*]], 4
+; CHECK-NEXT: br i1 [[OR_COND]], label [[IF_THEN:%.*]], label [[RETURN:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: switch i32 [[X]], label [[DEFAULT_UNREACHABLE:%.*]] [
+; CHECK-NEXT: i32 0, label [[SW_BB:%.*]]
+; CHECK-NEXT: i32 1, label [[SW_BB2:%.*]]
+; CHECK-NEXT: i32 2, label [[SW_BB4:%.*]]
+; CHECK-NEXT: i32 3, label [[SW_BB6:%.*]]
+; CHECK-NEXT: ]
+; CHECK: sw.bb:
+; CHECK-NEXT: [[CALL:%.*]] = tail call i32 @g(i32 2)
+; CHECK-NEXT: br label [[RETURN]]
+; CHECK: sw.bb2:
+; CHECK-NEXT: [[CALL3:%.*]] = tail call i32 @g(i32 3)
+; CHECK-NEXT: br label [[RETURN]]
+; CHECK: sw.bb4:
+; CHECK-NEXT: [[CALL5:%.*]] = tail call i32 @g(i32 4)
+; CHECK-NEXT: br label [[RETURN]]
+; CHECK: sw.bb6:
+; CHECK-NEXT: [[CALL7:%.*]] = tail call i32 @g(i32 5)
+; CHECK-NEXT: br label [[RETURN]]
+; CHECK: default.unreachable:
+; CHECK-NEXT: unreachable
+; CHECK: return:
+; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i32 [ [[CALL7]], [[SW_BB6]] ], [ [[CALL5]], [[SW_BB4]] ], [ [[CALL3]], [[SW_BB2]] ], [ [[CALL]], [[SW_BB]] ], [ -23, [[ENTRY:%.*]] ]
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+entry:
+ %or.cond = icmp ult i32 %x, 4
+ br i1 %or.cond, label %if.then, label %return
+
+if.then:
+ switch i32 %x, label %sw.epilog [
+ i32 0, label %sw.bb
+ i32 1, label %sw.bb2
+ i32 2, label %sw.bb4
+ i32 3, label %sw.bb6
+ ]
+
+sw.bb:
+ %call = tail call i32 @g(i32 2)
+ br label %return
+
+sw.bb2:
+ %call3 = tail call i32 @g(i32 3)
+ br label %return
+
+sw.bb4:
+ %call5 = tail call i32 @g(i32 4)
+ br label %return
+
+sw.bb6:
+ %call7 = tail call i32 @g(i32 5)
+ br label %return
+
+sw.epilog:
+ call void @foo()
+ br label %return
+
+return:
+ %retval.0 = phi i32 [ %call7, %sw.bb6 ], [ %call5, %sw.bb4 ], [ %call3, %sw.bb2 ], [ %call, %sw.bb ], [ -23, %sw.epilog ], [ -23, %entry ]
+ ret i32 %retval.0
+}
declare void @llvm.assume(i1)
|
dtcxzyw
added a commit
to dtcxzyw/llvm-opt-benchmark
that referenced
this pull request
Dec 23, 2023
|
Ping. |
|
What happens if the default is already unreachable? Will we replace it with a new unreachable block? It would be good to skip the update in that case. |
Hm, I guess this isn't so simple because we'll mark the block as dead and remove it. |
It may still be worth doing this to avoid spurious invalidation of CFG analyses, but it's not really related to this patch... |
dtcxzyw
added a commit
to dtcxzyw/llvm-opt-benchmark
that referenced
this pull request
Jan 7, 2024
dtcxzyw
force-pushed
the
sccp-reachable-default
branch
from
6238a96 to
c12b109
Compare
justinfargnoli
pushed a commit
to justinfargnoli/llvm-project
that referenced
this pull request
Jan 28, 2024
This patch eliminates unreachable default cases using range information. Fixes llvm#76085.
hiraditya
added a commit
to hiraditya/llvm-project
that referenced
this pull request
Aug 7, 2024
Additional testcase for llvm#76295
hiraditya
added a commit
to hiraditya/llvm-project
that referenced
this pull request
Aug 7, 2024
Additional testcase for llvm#76295
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This patch eliminates unreachable default cases using range information.
Fixes #76085.