[llvm] 449adaf - [InstCombine] Fold strnlen of constant strings.
Martin Sebor via llvm-commits
llvm-commits at lists.llvm.org
Tue Apr 26 15:16:02 PDT 2022
Author: Martin Sebor
Date: 2022-04-26T16:15:28-06:00
New Revision: 449adafabe46ded951bf9bcde9c88c883c8aa0e6
URL: https://github.com/llvm/llvm-project/commit/449adafabe46ded951bf9bcde9c88c883c8aa0e6
DIFF: https://github.com/llvm/llvm-project/commit/449adafabe46ded951bf9bcde9c88c883c8aa0e6.diff
LOG: [InstCombine] Fold strnlen of constant strings.
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D123817
Added:
Modified:
llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
llvm/test/Transforms/InstCombine/strnlen-1.ll
llvm/test/Transforms/InstCombine/strnlen-3.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 312aebf46db7c..a948a554e2799 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -632,6 +632,7 @@ Value *LibCallSimplifier::optimizeStringLength(CallInst *CI, IRBuilderBase &B,
unsigned CharSize,
Value *Bound) {
Value *Src = CI->getArgOperand(0);
+ Type *CharTy = B.getIntNTy(CharSize);
if (Bound) {
if (ConstantInt *BoundCst = dyn_cast<ConstantInt>(Bound)) {
@@ -641,20 +642,26 @@ Value *LibCallSimplifier::optimizeStringLength(CallInst *CI, IRBuilderBase &B,
if (BoundCst->isOne()) {
// Fold strnlen(s, 1) -> *s ? 1 : 0 for any s.
- Type *CharTy = B.getIntNTy(CharSize);
Value *CharVal = B.CreateLoad(CharTy, Src, "strnlen.char0");
Value *ZeroChar = ConstantInt::get(CharTy, 0);
Value *Cmp = B.CreateICmpNE(CharVal, ZeroChar, "strnlen.char0cmp");
return B.CreateZExt(Cmp, CI->getType());
}
}
- // Otherwise punt for strnlen for now.
- return nullptr;
}
- // Constant folding: strlen("xyz") -> 3
- if (uint64_t Len = GetStringLength(Src, CharSize))
- return ConstantInt::get(CI->getType(), Len - 1);
+ if (uint64_t Len = GetStringLength(Src, CharSize)) {
+ Value *LenC = ConstantInt::get(CI->getType(), Len - 1);
+ // Fold strlen("xyz") -> 3 and strnlen("xyz", 2) -> 2
+ // and strnlen("xyz", Bound) -> min(3, Bound) for nonconstant Bound.
+ if (Bound)
+ return B.CreateBinaryIntrinsic(Intrinsic::umin, LenC, Bound);
+ return LenC;
+ }
+
+ if (Bound)
+ // Punt for strnlen for now.
+ return nullptr;
// If s is a constant pointer pointing to a string literal, we can fold
// strlen(s + x) to strlen(s) - x, when x is known to be in the range
diff --git a/llvm/test/Transforms/InstCombine/strnlen-1.ll b/llvm/test/Transforms/InstCombine/strnlen-1.ll
index d07e8ddb9893d..d17c11e21964c 100644
--- a/llvm/test/Transforms/InstCombine/strnlen-1.ll
+++ b/llvm/test/Transforms/InstCombine/strnlen-1.ll
@@ -95,8 +95,7 @@ define i64 @fold_strnlen_s5_0() {
define i64 @fold_strnlen_s5_4() {
; CHECK-LABEL: @fold_strnlen_s5_4(
-; CHECK-NEXT: [[LEN:%.*]] = call i64 @strnlen(i8* noundef nonnull dereferenceable(1) getelementptr inbounds ([6 x i8], [6 x i8]* @s5, i64 0, i64 0), i64 4)
-; CHECK-NEXT: ret i64 [[LEN]]
+; CHECK-NEXT: ret i64 4
;
%ptr = getelementptr [6 x i8], [6 x i8]* @s5, i32 0, i32 0
%len = call i64 @strnlen(i8* %ptr, i64 4)
@@ -108,8 +107,7 @@ define i64 @fold_strnlen_s5_4() {
define i64 @fold_strnlen_s5_5() {
; CHECK-LABEL: @fold_strnlen_s5_5(
-; CHECK-NEXT: [[LEN:%.*]] = call i64 @strnlen(i8* noundef nonnull dereferenceable(1) getelementptr inbounds ([6 x i8], [6 x i8]* @s5, i64 0, i64 0), i64 5)
-; CHECK-NEXT: ret i64 [[LEN]]
+; CHECK-NEXT: ret i64 5
;
%ptr = getelementptr [6 x i8], [6 x i8]* @s5, i32 0, i32 0
%len = call i64 @strnlen(i8* %ptr, i64 5)
@@ -121,8 +119,7 @@ define i64 @fold_strnlen_s5_5() {
define i64 @fold_strnlen_s5_m1() {
; CHECK-LABEL: @fold_strnlen_s5_m1(
-; CHECK-NEXT: [[LEN:%.*]] = call i64 @strnlen(i8* noundef nonnull dereferenceable(1) getelementptr inbounds ([6 x i8], [6 x i8]* @s5, i64 0, i64 0), i64 -1)
-; CHECK-NEXT: ret i64 [[LEN]]
+; CHECK-NEXT: ret i64 5
;
%ptr = getelementptr [6 x i8], [6 x i8]* @s5, i32 0, i32 0
%len = call i64 @strnlen(i8* %ptr, i64 -1)
@@ -134,8 +131,7 @@ define i64 @fold_strnlen_s5_m1() {
define i64 @fold_strnlen_s5_3_p4_5() {
; CHECK-LABEL: @fold_strnlen_s5_3_p4_5(
-; CHECK-NEXT: [[LEN:%.*]] = call i64 @strnlen(i8* noundef nonnull dereferenceable(1) getelementptr inbounds ([9 x i8], [9 x i8]* @s5_3, i64 0, i64 4), i64 5)
-; CHECK-NEXT: ret i64 [[LEN]]
+; CHECK-NEXT: ret i64 1
;
%ptr = getelementptr [9 x i8], [9 x i8]* @s5_3, i32 0, i32 4
%len = call i64 @strnlen(i8* %ptr, i64 5)
@@ -143,12 +139,11 @@ define i64 @fold_strnlen_s5_3_p4_5() {
}
-; Fold strnlen(s5_3 + 5, 5) to 1.
+; Fold strnlen(s5_3 + 5, 5) to 0.
define i64 @fold_strnlen_s5_3_p5_5() {
; CHECK-LABEL: @fold_strnlen_s5_3_p5_5(
-; CHECK-NEXT: [[LEN:%.*]] = call i64 @strnlen(i8* noundef nonnull dereferenceable(1) getelementptr inbounds ([9 x i8], [9 x i8]* @s5_3, i64 0, i64 5), i64 5)
-; CHECK-NEXT: ret i64 [[LEN]]
+; CHECK-NEXT: ret i64 0
;
%ptr = getelementptr [9 x i8], [9 x i8]* @s5_3, i32 0, i32 5
%len = call i64 @strnlen(i8* %ptr, i64 5)
@@ -160,8 +155,7 @@ define i64 @fold_strnlen_s5_3_p5_5() {
define i64 @fold_strnlen_s5_3_p6_5() {
; CHECK-LABEL: @fold_strnlen_s5_3_p6_5(
-; CHECK-NEXT: [[LEN:%.*]] = call i64 @strnlen(i8* noundef nonnull dereferenceable(1) getelementptr inbounds ([9 x i8], [9 x i8]* @s5_3, i64 0, i64 6), i64 5)
-; CHECK-NEXT: ret i64 [[LEN]]
+; CHECK-NEXT: ret i64 3
;
%ptr = getelementptr [9 x i8], [9 x i8]* @s5_3, i32 0, i32 6
%len = call i64 @strnlen(i8* %ptr, i64 5)
diff --git a/llvm/test/Transforms/InstCombine/strnlen-3.ll b/llvm/test/Transforms/InstCombine/strnlen-3.ll
index 585a69d1b6db0..877eae813c683 100644
--- a/llvm/test/Transforms/InstCombine/strnlen-3.ll
+++ b/llvm/test/Transforms/InstCombine/strnlen-3.ll
@@ -126,8 +126,8 @@ define i64 @call_strnlen_s5_3_pi_n(i64 zeroext %i, i64 %n) {
define i64 @fold_strnlen_a3_n(i64 %n) {
; CHECK-LABEL: @fold_strnlen_a3_n(
-; CHECK-NEXT: [[LEN:%.*]] = call i64 @strnlen(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @a3, i64 0, i64 0), i64 [[N:%.*]])
-; CHECK-NEXT: ret i64 [[LEN]]
+; CHECK-NEXT: [[TMP1:%.*]] = call i64 @llvm.umin.i64(i64 [[N:%.*]], i64 3)
+; CHECK-NEXT: ret i64 [[TMP1]]
;
%ptr = getelementptr [3 x i8], [3 x i8]* @a3, i64 0, i64 0
@@ -140,8 +140,8 @@ define i64 @fold_strnlen_a3_n(i64 %n) {
define i64 @fold_strnlen_s3_n(i64 %n) {
; CHECK-LABEL: @fold_strnlen_s3_n(
-; CHECK-NEXT: [[LEN:%.*]] = call i64 @strnlen(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @s3, i64 0, i64 0), i64 [[N:%.*]])
-; CHECK-NEXT: ret i64 [[LEN]]
+; CHECK-NEXT: [[TMP1:%.*]] = call i64 @llvm.umin.i64(i64 [[N:%.*]], i64 3)
+; CHECK-NEXT: ret i64 [[TMP1]]
;
%ptr = getelementptr [4 x i8], [4 x i8]* @s3, i64 0, i64 0
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