[llvm] [LoopIdiom] Update strlen idiom body loop condition to be clean up by LoopDeletion (PR #134906)
Henry Jiang via llvm-commits
llvm-commits at lists.llvm.org
Wed Apr 9 08:43:27 PDT 2025
https://github.com/mustartt updated https://github.com/llvm/llvm-project/pull/134906
>From c4746a9be717c13f4d4f4f568dfe82ef56366b20 Mon Sep 17 00:00:00 2001
From: Henry Jiang <henry.jiang1 at ibm.com>
Date: Tue, 8 Apr 2025 14:35:16 -0400
Subject: [PATCH 1/2] Update loop cond for cleanup by loop-delete
---
.../Transforms/Scalar/LoopIdiomRecognize.cpp | 9 ++++
.../Transforms/LoopIdiom/strlen-cleanup.ll | 43 +++++++++++++++++++
llvm/test/Transforms/LoopIdiom/strlen.ll | 12 +++---
llvm/test/Transforms/LoopIdiom/wcslen16.ll | 2 +-
llvm/test/Transforms/LoopIdiom/wcslen32.ll | 2 +-
5 files changed, 60 insertions(+), 8 deletions(-)
create mode 100644 llvm/test/Transforms/LoopIdiom/strlen-cleanup.ll
diff --git a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
index 4940dd8c47dde..d78a02381c68b 100644
--- a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -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)
@@ -1804,6 +1808,11 @@ bool LoopIdiomRecognize::recognizeAndInsertStrLen() {
// up by later passes
for (PHINode *PN : Cleanup)
RecursivelyDeleteDeadPHINode(PN);
+
+ ConstantInt *NewLoopCond = LoopTerm->getSuccessor(0) == LoopBody
+ ? Builder.getFalse()
+ : Builder.getTrue();
+ LoopTerm->setCondition(NewLoopCond);
SE->forgetLoop(CurLoop);
++NumStrLen;
diff --git a/llvm/test/Transforms/LoopIdiom/strlen-cleanup.ll b/llvm/test/Transforms/LoopIdiom/strlen-cleanup.ll
new file mode 100644
index 0000000000000..60b5ac6ce1d78
--- /dev/null
+++ b/llvm/test/Transforms/LoopIdiom/strlen-cleanup.ll
@@ -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}
+
diff --git a/llvm/test/Transforms/LoopIdiom/strlen.ll b/llvm/test/Transforms/LoopIdiom/strlen.ll
index c1141177c659f..3b9d33ebdc74e 100644
--- a/llvm/test/Transforms/LoopIdiom/strlen.ll
+++ b/llvm/test/Transforms/LoopIdiom/strlen.ll
@@ -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
@@ -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
@@ -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]]:
@@ -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]]
@@ -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]]
@@ -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]]:
diff --git a/llvm/test/Transforms/LoopIdiom/wcslen16.ll b/llvm/test/Transforms/LoopIdiom/wcslen16.ll
index 8be51869f1f2e..cd8a31f4af3dd 100644
--- a/llvm/test/Transforms/LoopIdiom/wcslen16.ll
+++ b/llvm/test/Transforms/LoopIdiom/wcslen16.ll
@@ -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
diff --git a/llvm/test/Transforms/LoopIdiom/wcslen32.ll b/llvm/test/Transforms/LoopIdiom/wcslen32.ll
index 2c7ceb4d187e6..f1cddf9424ffd 100644
--- a/llvm/test/Transforms/LoopIdiom/wcslen32.ll
+++ b/llvm/test/Transforms/LoopIdiom/wcslen32.ll
@@ -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
>From 6918d2cc7c0da29c8033c592f66af932f803ffd5 Mon Sep 17 00:00:00 2001
From: Henry Jiang <henry.jiang1 at ibm.com>
Date: Wed, 9 Apr 2025 11:36:18 -0400
Subject: [PATCH 2/2] Address review comments
---
llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
index d78a02381c68b..eacc67cd5a475 100644
--- a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -1809,6 +1809,12 @@ bool LoopIdiomRecognize::recognizeAndInsertStrLen() {
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
? Builder.getFalse()
: Builder.getTrue();
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