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[LoopIdiom] Update strlen idiom body loop condition to be clean up by LoopDeletion #134906

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Merged
merged 2 commits into from
Apr 11, 2025
Merged

[LoopIdiom] Update strlen idiom body loop condition to be clean up by LoopDeletion #134906

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c4746a9
Update loop cond for cleanup by loop-delete
mustartt Apr 8, 2025
6918d2c
Address review comments
mustartt Apr 9, 2025
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15 changes: 15 additions & 0 deletions llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1745,7 +1745,11 @@ bool LoopIdiomRecognize::recognizeAndInsertStrLen() {
return false;

BasicBlock *Preheader = CurLoop->getLoopPreheader();
BasicBlock *LoopBody = *CurLoop->block_begin();
BasicBlock *LoopExitBB = CurLoop->getExitBlock();
BranchInst *LoopTerm = dyn_cast<BranchInst>(LoopBody->getTerminator());
assert(Preheader && LoopBody && LoopExitBB && LoopTerm &&
"Should be verified to be valid by StrlenVerifier");

if (Verifier.OpWidth == 8) {
if (DisableLIRP::Strlen)
Expand Down Expand Up @@ -1804,6 +1808,17 @@ bool LoopIdiomRecognize::recognizeAndInsertStrLen() {
// up by later passes
for (PHINode *PN : Cleanup)
RecursivelyDeleteDeadPHINode(PN);

// LoopDeletion only delete invariant loops with known trip-count. We can
// update the condition so it will reliablely delete the invariant loop
assert(LoopTerm->getNumSuccessors() == 2 &&
(LoopTerm->getSuccessor(0) == LoopBody ||
LoopTerm->getSuccessor(1) == LoopBody) &&
"loop body must have a successor that is it self");
ConstantInt *NewLoopCond = LoopTerm->getSuccessor(0) == LoopBody
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Consider adding a comment explaining that this intends to make the old code unreachable/dead.

Add assert that at least one of the successors is LoopBody?

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Thanks for taking a look. I added the asserts and comments.

I will take a look to see if there's any further testing required.

? Builder.getFalse()
: Builder.getTrue();
LoopTerm->setCondition(NewLoopCond);
SE->forgetLoop(CurLoop);

++NumStrLen;
Expand Down
43 changes: 43 additions & 0 deletions llvm/test/Transforms/LoopIdiom/strlen-cleanup.ll
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@@ -0,0 +1,43 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt < %s -S -passes=loop-idiom,loop-deletion | FileCheck %s

define [2 x i64] @convert_null_terminated_to_bounded_ptr(ptr noundef %p) {
; CHECK-LABEL: define [2 x i64] @convert_null_terminated_to_bounded_ptr(
; CHECK-SAME: ptr noundef [[P:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[WCSLEN:%.*]] = call i64 @wcslen(ptr [[P]])
; CHECK-NEXT: br label %[[TERMINATED_BY_LOOP_END:.*]]
; CHECK: [[TERMINATED_BY_LOOP_END]]:
; CHECK-NEXT: [[TMP0:%.*]] = getelementptr inbounds i32, ptr [[P]], i64 [[WCSLEN]]
; CHECK-NEXT: [[TERMINATED_BY_UPPER:%.*]] = getelementptr i8, ptr [[TMP0]], i64 4
; CHECK-NEXT: [[TMP1:%.*]] = ptrtoint ptr [[P]] to i64
; CHECK-NEXT: [[DOTFCA_0_INSERT:%.*]] = insertvalue [2 x i64] poison, i64 [[TMP1]], 0
; CHECK-NEXT: [[TMP2:%.*]] = ptrtoint ptr [[TERMINATED_BY_UPPER]] to i64
; CHECK-NEXT: [[DOTFCA_1_INSERT:%.*]] = insertvalue [2 x i64] [[DOTFCA_0_INSERT]], i64 [[TMP2]], 1
; CHECK-NEXT: ret [2 x i64] [[DOTFCA_1_INSERT]]
;
entry:
br label %terminated_by.loop_cond

terminated_by.loop_cond: ; preds = %terminated_by.loop_cond, %entry
%terminated_by.len.0 = phi i64 [ 0, %entry ], [ %terminated_by.new_len, %terminated_by.loop_cond ]
%0 = getelementptr inbounds i32, ptr %p, i64 %terminated_by.len.0
%terminated_by.elem = load i32, ptr %0, align 4
%terminted_by.check_terminator = icmp eq i32 %terminated_by.elem, 0
%terminated_by.new_len = add i64 %terminated_by.len.0, 1
br i1 %terminted_by.check_terminator, label %terminated_by.loop_end, label %terminated_by.loop_cond

terminated_by.loop_end: ; preds = %terminated_by.loop_cond
%1 = getelementptr inbounds i32, ptr %p, i64 %terminated_by.len.0
%terminated_by.upper = getelementptr i8, ptr %1, i64 4
%2 = ptrtoint ptr %p to i64
%.fca.0.insert = insertvalue [2 x i64] poison, i64 %2, 0
%3 = ptrtoint ptr %terminated_by.upper to i64
%.fca.1.insert = insertvalue [2 x i64] %.fca.0.insert, i64 %3, 1
ret [2 x i64] %.fca.1.insert
}

!llvm.module.flags = !{!0}

!0 = !{i32 1, !"wchar_size", i32 4}

12 changes: 6 additions & 6 deletions llvm/test/Transforms/LoopIdiom/strlen.ll
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Expand Up @@ -24,7 +24,7 @@ define i64 @valid_basic_strlen(ptr %str) {
; CHECK-NEXT: [[TMP0:%.*]] = load i8, ptr [[STR_ADDR_0]], align 1
; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp eq i8 [[TMP0]], 0
; CHECK-NEXT: [[INCDEC_PTR]] = getelementptr i8, ptr [[STR_ADDR_0]], i64 1
; CHECK-NEXT: br i1 [[CMP_NOT]], label %[[WHILE_END:.*]], label %[[WHILE_COND]]
; CHECK-NEXT: br i1 true, label %[[WHILE_END:.*]], label %[[WHILE_COND]]
; CHECK: [[WHILE_END]]:
; CHECK-NEXT: [[SUB_PTR_LHS_CAST:%.*]] = ptrtoint ptr [[SCEVGEP]] to i64
; CHECK-NEXT: [[SUB_PTR_RHS_CAST:%.*]] = ptrtoint ptr [[STR]] to i64
Expand Down Expand Up @@ -74,7 +74,7 @@ define i32 @valid_basic_strlen_rotated(ptr %str) {
; CHECK-NEXT: [[INCDEC_PTR]] = getelementptr inbounds nuw i8, ptr [[STR_ADDR_0]], i64 1
; CHECK-NEXT: [[TMP2:%.*]] = load i8, ptr [[INCDEC_PTR]], align 1
; CHECK-NEXT: [[TOBOOL1_NOT:%.*]] = icmp eq i8 [[TMP2]], 0
; CHECK-NEXT: br i1 [[TOBOOL1_NOT]], label %[[DO_END:.*]], label %[[DO_BODY]]
; CHECK-NEXT: br i1 true, label %[[DO_END:.*]], label %[[DO_BODY]]
; CHECK: [[DO_END]]:
; CHECK-NEXT: [[SUB_PTR_LHS_CAST:%.*]] = ptrtoint ptr [[SCEVGEP1]] to i64
; CHECK-NEXT: [[SUB_PTR_RHS_CAST:%.*]] = ptrtoint ptr [[STR]] to i64
Expand Down Expand Up @@ -163,7 +163,7 @@ define dso_local void @valid_strlen_with_aux_indvar(ptr noundef %str, ptr nounde
; CHECK-NEXT: [[INCDEC_PTR2]] = getelementptr inbounds nuw i8, ptr [[FOO_ADDR_011]], i64 1
; CHECK-NEXT: [[TMP10:%.*]] = load i8, ptr [[INCDEC_PTR]], align 1
; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i8 [[TMP10]], 0
; CHECK-NEXT: br i1 [[TOBOOL_NOT]], label %[[WHILE_END_LOOPEXIT:.*]], label %[[WHILE_BODY]]
; CHECK-NEXT: br i1 true, label %[[WHILE_END_LOOPEXIT:.*]], label %[[WHILE_BODY]]
; CHECK: [[WHILE_END_LOOPEXIT]]:
; CHECK-NEXT: br label %[[WHILE_END]]
; CHECK: [[WHILE_END]]:
Expand Down Expand Up @@ -232,7 +232,7 @@ define i32 @valid_strlen_index(ptr %str) {
; CHECK-NEXT: [[TMP0:%.*]] = load i8, ptr [[ARRAYIDX]], align 1
; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i8 [[TMP0]], 0
; CHECK-NEXT: [[INDVARS_IV_NEXT]] = add nuw nsw i64 [[INDVARS_IV]], 1
; CHECK-NEXT: br i1 [[TOBOOL_NOT]], label %[[WHILE_END:.*]], label %[[WHILE_COND]]
; CHECK-NEXT: br i1 true, label %[[WHILE_END:.*]], label %[[WHILE_COND]]
; CHECK: [[WHILE_END]]:
; CHECK-NEXT: [[TMP1:%.*]] = trunc nuw nsw i64 [[STRLEN]] to i32
; CHECK-NEXT: ret i32 [[TMP1]]
Expand Down Expand Up @@ -290,7 +290,7 @@ define dso_local void @valid_strlen_offset(ptr noundef %str) local_unnamed_addr
; CHECK-NEXT: [[TMP4:%.*]] = load i8, ptr [[STR_ADDR_0]], align 1
; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i8 [[TMP4]], 0
; CHECK-NEXT: [[INCDEC_PTR14]] = getelementptr inbounds nuw i8, ptr [[STR_ADDR_0]], i64 1
; CHECK-NEXT: br i1 [[TOBOOL_NOT]], label %[[WHILE_END:.*]], label %[[WHILE_COND]]
; CHECK-NEXT: br i1 true, label %[[WHILE_END:.*]], label %[[WHILE_COND]]
; CHECK: [[WHILE_END]]:
; CHECK-NEXT: tail call void @use(ptr noundef nonnull [[SCEVGEP]])
; CHECK-NEXT: br label %[[RETURN]]
Expand Down Expand Up @@ -377,7 +377,7 @@ define void @valid_nested_idiom(ptr %strs, i32 %n) {
; CHECK-NEXT: [[INC]] = add nuw nsw i32 [[COUNT_08]], 1
; CHECK-NEXT: [[TMP4:%.*]] = load i8, ptr [[INCDEC_PTR]], align 1
; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i8 [[TMP4]], 0
; CHECK-NEXT: br i1 [[TOBOOL_NOT]], label %[[WHILE_END_LOOPEXIT:.*]], label %[[WHILE_BODY]]
; CHECK-NEXT: br i1 true, label %[[WHILE_END_LOOPEXIT:.*]], label %[[WHILE_BODY]]
; CHECK: [[WHILE_END_LOOPEXIT]]:
; CHECK-NEXT: br label %[[WHILE_END]]
; CHECK: [[WHILE_END]]:
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/Transforms/LoopIdiom/wcslen16.ll
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Expand Up @@ -26,7 +26,7 @@ define i64 @valid_strlen16(ptr %src) {
; CHECK-NEXT: [[CURR_0]] = getelementptr inbounds i8, ptr [[SRC_PN]], i64 2
; CHECK-NEXT: [[TMP3:%.*]] = load i16, ptr [[CURR_0]], align 2
; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i16 [[TMP3]], 0
; CHECK-NEXT: br i1 [[TOBOOL_NOT]], label %[[WHILE_END:.*]], label %[[WHILE_COND]]
; CHECK-NEXT: br i1 true, label %[[WHILE_END:.*]], label %[[WHILE_COND]]
; CHECK: [[WHILE_END]]:
; CHECK-NEXT: [[SUB_PTR_LHS_CAST:%.*]] = ptrtoint ptr [[END]] to i64
; CHECK-NEXT: [[SUB_PTR_RHS_CAST:%.*]] = ptrtoint ptr [[SRC]] to i64
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/Transforms/LoopIdiom/wcslen32.ll
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Expand Up @@ -26,7 +26,7 @@ define i64 @valid_wcslen32(ptr %src) {
; CHECK-NEXT: [[CURR_0]] = getelementptr inbounds i8, ptr [[SRC_PN]], i64 4
; CHECK-NEXT: [[TMP3:%.*]] = load i32, ptr [[CURR_0]], align 4
; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i32 [[TMP3]], 0
; CHECK-NEXT: br i1 [[TOBOOL_NOT]], label %[[WHILE_END:.*]], label %[[WHILE_COND]]
; CHECK-NEXT: br i1 true, label %[[WHILE_END:.*]], label %[[WHILE_COND]]
; CHECK: [[WHILE_END]]:
; CHECK-NEXT: [[SUB_PTR_LHS_CAST:%.*]] = ptrtoint ptr [[END]] to i64
; CHECK-NEXT: [[SUB_PTR_RHS_CAST:%.*]] = ptrtoint ptr [[SRC]] to i64
Expand Down