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[LoopIdiom] Update strlen idiom body loop condition to be clean up by LoopDeletion (#134906)
Fixes the case where subsequent passes were unable to find and delete the invariant loop left over by the strlen idiom conversion. Since `loop-deletion` only operate on computable loops, we can update the loop condition to something more easily picked up by `loop-deletion` As pointed out in #134736
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5 files changed

+66
-8
lines changed

5 files changed

+66
-8
lines changed

‎llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp‎

Lines changed: 15 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1745,7 +1745,11 @@ bool LoopIdiomRecognize::recognizeAndInsertStrLen() {
17451745
return false;
17461746

17471747
BasicBlock *Preheader = CurLoop->getLoopPreheader();
1748+
BasicBlock *LoopBody = *CurLoop->block_begin();
17481749
BasicBlock *LoopExitBB = CurLoop->getExitBlock();
1750+
BranchInst *LoopTerm = dyn_cast<BranchInst>(LoopBody->getTerminator());
1751+
assert(Preheader && LoopBody && LoopExitBB && LoopTerm &&
1752+
"Should be verified to be valid by StrlenVerifier");
17491753

17501754
if (Verifier.OpWidth == 8) {
17511755
if (DisableLIRP::Strlen)
@@ -1804,6 +1808,17 @@ bool LoopIdiomRecognize::recognizeAndInsertStrLen() {
18041808
// up by later passes
18051809
for (PHINode *PN : Cleanup)
18061810
RecursivelyDeleteDeadPHINode(PN);
1811+
1812+
// LoopDeletion only delete invariant loops with known trip-count. We can
1813+
// update the condition so it will reliablely delete the invariant loop
1814+
assert(LoopTerm->getNumSuccessors() == 2 &&
1815+
(LoopTerm->getSuccessor(0) == LoopBody ||
1816+
LoopTerm->getSuccessor(1) == LoopBody) &&
1817+
"loop body must have a successor that is it self");
1818+
ConstantInt *NewLoopCond = LoopTerm->getSuccessor(0) == LoopBody
1819+
? Builder.getFalse()
1820+
: Builder.getTrue();
1821+
LoopTerm->setCondition(NewLoopCond);
18071822
SE->forgetLoop(CurLoop);
18081823

18091824
++NumStrLen;

‎llvm/test/Transforms/LoopIdiom/strlen-cleanup.ll‎

Lines changed: 43 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,43 @@
1+
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
2+
; RUN: opt < %s -S -passes=loop-idiom,loop-deletion | FileCheck %s
3+
4+
define [2 x i64] @convert_null_terminated_to_bounded_ptr(ptr noundef %p) {
5+
; CHECK-LABEL: define [2 x i64] @convert_null_terminated_to_bounded_ptr(
6+
; CHECK-SAME: ptr noundef [[P:%.*]]) {
7+
; CHECK-NEXT: [[ENTRY:.*:]]
8+
; CHECK-NEXT: [[WCSLEN:%.*]] = call i64 @wcslen(ptr [[P]])
9+
; CHECK-NEXT: br label %[[TERMINATED_BY_LOOP_END:.*]]
10+
; CHECK: [[TERMINATED_BY_LOOP_END]]:
11+
; CHECK-NEXT: [[TMP0:%.*]] = getelementptr inbounds i32, ptr [[P]], i64 [[WCSLEN]]
12+
; CHECK-NEXT: [[TERMINATED_BY_UPPER:%.*]] = getelementptr i8, ptr [[TMP0]], i64 4
13+
; CHECK-NEXT: [[TMP1:%.*]] = ptrtoint ptr [[P]] to i64
14+
; CHECK-NEXT: [[DOTFCA_0_INSERT:%.*]] = insertvalue [2 x i64] poison, i64 [[TMP1]], 0
15+
; CHECK-NEXT: [[TMP2:%.*]] = ptrtoint ptr [[TERMINATED_BY_UPPER]] to i64
16+
; CHECK-NEXT: [[DOTFCA_1_INSERT:%.*]] = insertvalue [2 x i64] [[DOTFCA_0_INSERT]], i64 [[TMP2]], 1
17+
; CHECK-NEXT: ret [2 x i64] [[DOTFCA_1_INSERT]]
18+
;
19+
entry:
20+
br label %terminated_by.loop_cond
21+
22+
terminated_by.loop_cond: ; preds = %terminated_by.loop_cond, %entry
23+
%terminated_by.len.0 = phi i64 [ 0, %entry ], [ %terminated_by.new_len, %terminated_by.loop_cond ]
24+
%0 = getelementptr inbounds i32, ptr %p, i64 %terminated_by.len.0
25+
%terminated_by.elem = load i32, ptr %0, align 4
26+
%terminted_by.check_terminator = icmp eq i32 %terminated_by.elem, 0
27+
%terminated_by.new_len = add i64 %terminated_by.len.0, 1
28+
br i1 %terminted_by.check_terminator, label %terminated_by.loop_end, label %terminated_by.loop_cond
29+
30+
terminated_by.loop_end: ; preds = %terminated_by.loop_cond
31+
%1 = getelementptr inbounds i32, ptr %p, i64 %terminated_by.len.0
32+
%terminated_by.upper = getelementptr i8, ptr %1, i64 4
33+
%2 = ptrtoint ptr %p to i64
34+
%.fca.0.insert = insertvalue [2 x i64] poison, i64 %2, 0
35+
%3 = ptrtoint ptr %terminated_by.upper to i64
36+
%.fca.1.insert = insertvalue [2 x i64] %.fca.0.insert, i64 %3, 1
37+
ret [2 x i64] %.fca.1.insert
38+
}
39+
40+
!llvm.module.flags = !{!0}
41+
42+
!0 = !{i32 1, !"wchar_size", i32 4}
43+

‎llvm/test/Transforms/LoopIdiom/strlen.ll‎

Lines changed: 6 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -24,7 +24,7 @@ define i64 @valid_basic_strlen(ptr %str) {
2424
; CHECK-NEXT: [[TMP0:%.*]] = load i8, ptr [[STR_ADDR_0]], align 1
2525
; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp eq i8 [[TMP0]], 0
2626
; CHECK-NEXT: [[INCDEC_PTR]] = getelementptr i8, ptr [[STR_ADDR_0]], i64 1
27-
; CHECK-NEXT: br i1 [[CMP_NOT]], label %[[WHILE_END:.*]], label %[[WHILE_COND]]
27+
; CHECK-NEXT: br i1 true, label %[[WHILE_END:.*]], label %[[WHILE_COND]]
2828
; CHECK: [[WHILE_END]]:
2929
; CHECK-NEXT: [[SUB_PTR_LHS_CAST:%.*]] = ptrtoint ptr [[SCEVGEP]] to i64
3030
; CHECK-NEXT: [[SUB_PTR_RHS_CAST:%.*]] = ptrtoint ptr [[STR]] to i64
@@ -74,7 +74,7 @@ define i32 @valid_basic_strlen_rotated(ptr %str) {
7474
; CHECK-NEXT: [[INCDEC_PTR]] = getelementptr inbounds nuw i8, ptr [[STR_ADDR_0]], i64 1
7575
; CHECK-NEXT: [[TMP2:%.*]] = load i8, ptr [[INCDEC_PTR]], align 1
7676
; CHECK-NEXT: [[TOBOOL1_NOT:%.*]] = icmp eq i8 [[TMP2]], 0
77-
; CHECK-NEXT: br i1 [[TOBOOL1_NOT]], label %[[DO_END:.*]], label %[[DO_BODY]]
77+
; CHECK-NEXT: br i1 true, label %[[DO_END:.*]], label %[[DO_BODY]]
7878
; CHECK: [[DO_END]]:
7979
; CHECK-NEXT: [[SUB_PTR_LHS_CAST:%.*]] = ptrtoint ptr [[SCEVGEP1]] to i64
8080
; CHECK-NEXT: [[SUB_PTR_RHS_CAST:%.*]] = ptrtoint ptr [[STR]] to i64
@@ -163,7 +163,7 @@ define dso_local void @valid_strlen_with_aux_indvar(ptr noundef %str, ptr nounde
163163
; CHECK-NEXT: [[INCDEC_PTR2]] = getelementptr inbounds nuw i8, ptr [[FOO_ADDR_011]], i64 1
164164
; CHECK-NEXT: [[TMP10:%.*]] = load i8, ptr [[INCDEC_PTR]], align 1
165165
; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i8 [[TMP10]], 0
166-
; CHECK-NEXT: br i1 [[TOBOOL_NOT]], label %[[WHILE_END_LOOPEXIT:.*]], label %[[WHILE_BODY]]
166+
; CHECK-NEXT: br i1 true, label %[[WHILE_END_LOOPEXIT:.*]], label %[[WHILE_BODY]]
167167
; CHECK: [[WHILE_END_LOOPEXIT]]:
168168
; CHECK-NEXT: br label %[[WHILE_END]]
169169
; CHECK: [[WHILE_END]]:
@@ -232,7 +232,7 @@ define i32 @valid_strlen_index(ptr %str) {
232232
; CHECK-NEXT: [[TMP0:%.*]] = load i8, ptr [[ARRAYIDX]], align 1
233233
; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i8 [[TMP0]], 0
234234
; CHECK-NEXT: [[INDVARS_IV_NEXT]] = add nuw nsw i64 [[INDVARS_IV]], 1
235-
; CHECK-NEXT: br i1 [[TOBOOL_NOT]], label %[[WHILE_END:.*]], label %[[WHILE_COND]]
235+
; CHECK-NEXT: br i1 true, label %[[WHILE_END:.*]], label %[[WHILE_COND]]
236236
; CHECK: [[WHILE_END]]:
237237
; CHECK-NEXT: [[TMP1:%.*]] = trunc nuw nsw i64 [[STRLEN]] to i32
238238
; CHECK-NEXT: ret i32 [[TMP1]]
@@ -290,7 +290,7 @@ define dso_local void @valid_strlen_offset(ptr noundef %str) local_unnamed_addr
290290
; CHECK-NEXT: [[TMP4:%.*]] = load i8, ptr [[STR_ADDR_0]], align 1
291291
; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i8 [[TMP4]], 0
292292
; CHECK-NEXT: [[INCDEC_PTR14]] = getelementptr inbounds nuw i8, ptr [[STR_ADDR_0]], i64 1
293-
; CHECK-NEXT: br i1 [[TOBOOL_NOT]], label %[[WHILE_END:.*]], label %[[WHILE_COND]]
293+
; CHECK-NEXT: br i1 true, label %[[WHILE_END:.*]], label %[[WHILE_COND]]
294294
; CHECK: [[WHILE_END]]:
295295
; CHECK-NEXT: tail call void @use(ptr noundef nonnull [[SCEVGEP]])
296296
; CHECK-NEXT: br label %[[RETURN]]
@@ -377,7 +377,7 @@ define void @valid_nested_idiom(ptr %strs, i32 %n) {
377377
; CHECK-NEXT: [[INC]] = add nuw nsw i32 [[COUNT_08]], 1
378378
; CHECK-NEXT: [[TMP4:%.*]] = load i8, ptr [[INCDEC_PTR]], align 1
379379
; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i8 [[TMP4]], 0
380-
; CHECK-NEXT: br i1 [[TOBOOL_NOT]], label %[[WHILE_END_LOOPEXIT:.*]], label %[[WHILE_BODY]]
380+
; CHECK-NEXT: br i1 true, label %[[WHILE_END_LOOPEXIT:.*]], label %[[WHILE_BODY]]
381381
; CHECK: [[WHILE_END_LOOPEXIT]]:
382382
; CHECK-NEXT: br label %[[WHILE_END]]
383383
; CHECK: [[WHILE_END]]:

‎llvm/test/Transforms/LoopIdiom/wcslen16.ll‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -26,7 +26,7 @@ define i64 @valid_strlen16(ptr %src) {
2626
; CHECK-NEXT: [[CURR_0]] = getelementptr inbounds i8, ptr [[SRC_PN]], i64 2
2727
; CHECK-NEXT: [[TMP3:%.*]] = load i16, ptr [[CURR_0]], align 2
2828
; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i16 [[TMP3]], 0
29-
; CHECK-NEXT: br i1 [[TOBOOL_NOT]], label %[[WHILE_END:.*]], label %[[WHILE_COND]]
29+
; CHECK-NEXT: br i1 true, label %[[WHILE_END:.*]], label %[[WHILE_COND]]
3030
; CHECK: [[WHILE_END]]:
3131
; CHECK-NEXT: [[SUB_PTR_LHS_CAST:%.*]] = ptrtoint ptr [[END]] to i64
3232
; CHECK-NEXT: [[SUB_PTR_RHS_CAST:%.*]] = ptrtoint ptr [[SRC]] to i64

‎llvm/test/Transforms/LoopIdiom/wcslen32.ll‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -26,7 +26,7 @@ define i64 @valid_wcslen32(ptr %src) {
2626
; CHECK-NEXT: [[CURR_0]] = getelementptr inbounds i8, ptr [[SRC_PN]], i64 4
2727
; CHECK-NEXT: [[TMP3:%.*]] = load i32, ptr [[CURR_0]], align 4
2828
; CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i32 [[TMP3]], 0
29-
; CHECK-NEXT: br i1 [[TOBOOL_NOT]], label %[[WHILE_END:.*]], label %[[WHILE_COND]]
29+
; CHECK-NEXT: br i1 true, label %[[WHILE_END:.*]], label %[[WHILE_COND]]
3030
; CHECK: [[WHILE_END]]:
3131
; CHECK-NEXT: [[SUB_PTR_LHS_CAST:%.*]] = ptrtoint ptr [[END]] to i64
3232
; CHECK-NEXT: [[SUB_PTR_RHS_CAST:%.*]] = ptrtoint ptr [[SRC]] to i64

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