test/Transforms/InstCombine/strlen-1.ll - llvm-project/llvm - Git at Google

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; Test that the strlen library call simplifier works correctly.
 ;
 ; RUN: opt < %s -passes=instcombine -S | FileCheck %s

 target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"

 @hello = constant [6 x i8] c"hello\00"
 @longer = constant [7 x i8] c"longer\00"
 @null = constant [1 x i8] zeroinitializer
 @null_hello = constant [7 x i8] c"\00hello\00"
 @nullstring = constant i8 0
 @a = common global [32 x i8] zeroinitializer, align 1
 @null_hello_mid = constant [13 x i8] c"hello wor\00ld\00"

 declare i32 @strlen(ptr)

 ; Check strlen(string constant) -> integer constant.

 define i32 @test_simplify1() {
 ; CHECK-LABEL: @test_simplify1(
 ; CHECK-NEXT:    ret i32 5
 ;
   %hello_l = call i32 @strlen(ptr @hello)
   ret i32 %hello_l
 }

 define i32 @test_simplify2() {
 ; CHECK-LABEL: @test_simplify2(
 ; CHECK-NEXT:    ret i32 0
 ;
   %null_l = call i32 @strlen(ptr @null)
   ret i32 %null_l
 }

 define i32 @test_simplify3() {
 ; CHECK-LABEL: @test_simplify3(
 ; CHECK-NEXT:    ret i32 0
 ;
   %null_hello_l = call i32 @strlen(ptr @null_hello)
   ret i32 %null_hello_l
 }

 define i32 @test_simplify4() {
 ; CHECK-LABEL: @test_simplify4(
 ; CHECK-NEXT:    ret i32 0
 ;
   %len = tail call i32 @strlen(ptr @nullstring) nounwind
   ret i32 %len
 }

 ; Check strlen(x) == 0 --> *x == 0.

 define i1 @test_simplify5() {
 ; CHECK-LABEL: @test_simplify5(
 ; CHECK-NEXT:    ret i1 false
 ;
   %hello_l = call i32 @strlen(ptr @hello)
   %eq_hello = icmp eq i32 %hello_l, 0
   ret i1 %eq_hello
 }

 define i1 @test_simplify6(ptr %str_p) {
 ; CHECK-LABEL: @test_simplify6(
 ; CHECK-NEXT:    [[CHAR0:%.*]] = load i8, ptr [[STR_P:%.*]], align 1
 ; CHECK-NEXT:    [[EQ_NULL:%.*]] = icmp eq i8 [[CHAR0]], 0
 ; CHECK-NEXT:    ret i1 [[EQ_NULL]]
 ;
   %str_l = call i32 @strlen(ptr %str_p)
   %eq_null = icmp eq i32 %str_l, 0
   ret i1 %eq_null
 }

 ; Check strlen(x) != 0 --> *x != 0.

 define i1 @test_simplify7() {
 ; CHECK-LABEL: @test_simplify7(
 ; CHECK-NEXT:    ret i1 true
 ;
   %hello_l = call i32 @strlen(ptr @hello)
   %ne_hello = icmp ne i32 %hello_l, 0
   ret i1 %ne_hello
 }

 define i1 @test_simplify8(ptr %str_p) {
 ; CHECK-LABEL: @test_simplify8(
 ; CHECK-NEXT:    [[CHAR0:%.*]] = load i8, ptr [[STR_P:%.*]], align 1
 ; CHECK-NEXT:    [[NE_NULL:%.*]] = icmp ne i8 [[CHAR0]], 0
 ; CHECK-NEXT:    ret i1 [[NE_NULL]]
 ;
   %str_l = call i32 @strlen(ptr %str_p)
   %ne_null = icmp ne i32 %str_l, 0
   ret i1 %ne_null
 }

 define i32 @test_simplify9(i1 %x) {
 ; CHECK-LABEL: @test_simplify9(
 ; CHECK-NEXT:    [[L:%.*]] = select i1 [[X:%.*]], i32 5, i32 6
 ; CHECK-NEXT:    ret i32 [[L]]
 ;
   %s = select i1 %x, ptr @hello, ptr @longer
   %l = call i32 @strlen(ptr %s)
   ret i32 %l
 }

 ; Check the case that should be simplified to a sub instruction.
 ; strlen(@hello + x) --> 5 - x

 define i32 @test_simplify10_inbounds(i32 %x) {
 ; CHECK-LABEL: @test_simplify10_inbounds(
 ; CHECK-NEXT:    [[HELLO_L:%.*]] = sub i32 5, [[X:%.*]]
 ; CHECK-NEXT:    ret i32 [[HELLO_L]]
 ;
   %hello_p = getelementptr inbounds [6 x i8], ptr @hello, i32 0, i32 %x
   %hello_l = call i32 @strlen(ptr %hello_p)
   ret i32 %hello_l
 }

 define i32 @test_simplify10_no_inbounds(i32 %x) {
 ; CHECK-LABEL: @test_simplify10_no_inbounds(
 ; CHECK-NEXT:    [[HELLO_L:%.*]] = sub i32 5, [[X:%.*]]
 ; CHECK-NEXT:    ret i32 [[HELLO_L]]
 ;
   %hello_p = getelementptr [6 x i8], ptr @hello, i32 0, i32 %x
   %hello_l = call i32 @strlen(ptr %hello_p)
   ret i32 %hello_l
 }

 ; strlen(@null_hello_mid + (x & 7)) --> 9 - (x & 7)

 define i32 @test_simplify11(i32 %x) {
 ; CHECK-LABEL: @test_simplify11(
 ; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X:%.*]], 7
 ; CHECK-NEXT:    [[HELLO_L:%.*]] = sub nuw nsw i32 9, [[AND]]
 ; CHECK-NEXT:    ret i32 [[HELLO_L]]
 ;
   %and = and i32 %x, 7
   %hello_p = getelementptr inbounds [13 x i8], ptr @null_hello_mid, i32 0, i32 %and
   %hello_l = call i32 @strlen(ptr %hello_p)
   ret i32 %hello_l
 }

 ; Check cases that shouldn't be simplified.

 define i32 @test_no_simplify1() {
 ; CHECK-LABEL: @test_no_simplify1(
 ; CHECK-NEXT:    [[A_L:%.*]] = call i32 @strlen(ptr noundef nonnull dereferenceable(1) @a)
 ; CHECK-NEXT:    ret i32 [[A_L]]
 ;
   %a_l = call i32 @strlen(ptr @a)
   ret i32 %a_l
 }

 ; strlen(@null_hello + x) should not be simplified to a sub instruction.

 define i32 @test_no_simplify2(i32 %x) {
 ; CHECK-LABEL: @test_no_simplify2(
 ; CHECK-NEXT:    [[HELLO_P:%.*]] = getelementptr inbounds [7 x i8], ptr @null_hello, i32 0, i32 [[X:%.*]]
 ; CHECK-NEXT:    [[HELLO_L:%.*]] = call i32 @strlen(ptr noundef nonnull dereferenceable(1) [[HELLO_P]])
 ; CHECK-NEXT:    ret i32 [[HELLO_L]]
 ;
   %hello_p = getelementptr inbounds [7 x i8], ptr @null_hello, i32 0, i32 %x
   %hello_l = call i32 @strlen(ptr %hello_p)
   ret i32 %hello_l
 }

 define i32 @test_no_simplify2_no_null_opt(i32 %x) #0 {
 ; CHECK-LABEL: @test_no_simplify2_no_null_opt(
 ; CHECK-NEXT:    [[HELLO_P:%.*]] = getelementptr inbounds [7 x i8], ptr @null_hello, i32 0, i32 [[X:%.*]]
 ; CHECK-NEXT:    [[HELLO_L:%.*]] = call i32 @strlen(ptr noundef [[HELLO_P]])
 ; CHECK-NEXT:    ret i32 [[HELLO_L]]
 ;
   %hello_p = getelementptr inbounds [7 x i8], ptr @null_hello, i32 0, i32 %x
   %hello_l = call i32 @strlen(ptr %hello_p)
   ret i32 %hello_l
 }

 ; strlen(@null_hello_mid + (x & 15)) should not be simplified to a sub instruction.

 define i32 @test_no_simplify3(i32 %x) {
 ; CHECK-LABEL: @test_no_simplify3(
 ; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X:%.*]], 15
 ; CHECK-NEXT:    [[HELLO_P:%.*]] = getelementptr inbounds [13 x i8], ptr @null_hello_mid, i32 0, i32 [[AND]]
 ; CHECK-NEXT:    [[HELLO_L:%.*]] = call i32 @strlen(ptr noundef nonnull dereferenceable(1) [[HELLO_P]])
 ; CHECK-NEXT:    ret i32 [[HELLO_L]]
 ;
   %and = and i32 %x, 15
   %hello_p = getelementptr inbounds [13 x i8], ptr @null_hello_mid, i32 0, i32 %and
   %hello_l = call i32 @strlen(ptr %hello_p)
   ret i32 %hello_l
 }

 define i32 @test_no_simplify3_on_null_opt(i32 %x) #0 {
 ; CHECK-LABEL: @test_no_simplify3_on_null_opt(
 ; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X:%.*]], 15
 ; CHECK-NEXT:    [[HELLO_P:%.*]] = getelementptr inbounds [13 x i8], ptr @null_hello_mid, i32 0, i32 [[AND]]
 ; CHECK-NEXT:    [[HELLO_L:%.*]] = call i32 @strlen(ptr noundef [[HELLO_P]])
 ; CHECK-NEXT:    ret i32 [[HELLO_L]]
 ;
   %and = and i32 %x, 15
   %hello_p = getelementptr inbounds [13 x i8], ptr @null_hello_mid, i32 0, i32 %and
   %hello_l = call i32 @strlen(ptr %hello_p)
   ret i32 %hello_l
 }

 define i32 @test1(ptr %str) {
 ; CHECK-LABEL: @test1(
 ; CHECK-NEXT:    [[LEN:%.*]] = tail call i32 @strlen(ptr noundef nonnull dereferenceable(1) [[STR:%.*]]) #[[ATTR1:[0-9]+]]
 ; CHECK-NEXT:    ret i32 [[LEN]]
 ;
   %len = tail call i32 @strlen(ptr %str) nounwind
   ret i32 %len
 }

 define i32 @test2(ptr %str) #0 {
 ; CHECK-LABEL: @test2(
 ; CHECK-NEXT:    [[LEN:%.*]] = tail call i32 @strlen(ptr noundef [[STR:%.*]]) #[[ATTR1]]
 ; CHECK-NEXT:    ret i32 [[LEN]]
 ;
   %len = tail call i32 @strlen(ptr %str) nounwind
   ret i32 %len
 }

 ; Test cases for PR47149.
 define i1 @strlen0_after_write_to_first_byte_global() {
 ; CHECK-LABEL: @strlen0_after_write_to_first_byte_global(
 ; CHECK-NEXT:    store i8 49, ptr @a, align 16
 ; CHECK-NEXT:    ret i1 false
 ;
   store i8 49, ptr @a, align 16
   %len = tail call i32 @strlen(ptr nonnull dereferenceable(1) @a)
   %cmp = icmp eq i32 %len, 0
   ret i1 %cmp
 }

 define i1 @strlen0_after_write_to_second_byte_global() {
 ; CHECK-LABEL: @strlen0_after_write_to_second_byte_global(
 ; CHECK-NEXT:    store i8 49, ptr getelementptr inbounds ([32 x i8], ptr @a, i32 0, i32 1), align 16
 ; CHECK-NEXT:    [[CHAR0:%.*]] = load i8, ptr @a, align 1
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[CHAR0]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   store i8 49, ptr getelementptr inbounds ([32 x i8], ptr @a, i64 0, i64 1), align 16
   %len = tail call i32 @strlen(ptr nonnull dereferenceable(1) @a)
   %cmp = icmp eq i32 %len, 0
   ret i1 %cmp
 }

 define i1 @strlen0_after_write_to_first_byte(ptr %ptr) {
 ; CHECK-LABEL: @strlen0_after_write_to_first_byte(
 ; CHECK-NEXT:    store i8 49, ptr [[PTR:%.*]], align 1
 ; CHECK-NEXT:    ret i1 false
 ;
   store i8 49, ptr %ptr
   %len = tail call i32 @strlen(ptr nonnull dereferenceable(1) %ptr)
   %cmp = icmp eq i32 %len, 0
   ret i1 %cmp
 }

 define i1 @strlen0_after_write_to_second_byte(ptr %ptr) {
 ; CHECK-LABEL: @strlen0_after_write_to_second_byte(
 ; CHECK-NEXT:    [[GEP:%.*]] = getelementptr i8, ptr [[PTR:%.*]], i32 1
 ; CHECK-NEXT:    store i8 49, ptr [[GEP]], align 1
 ; CHECK-NEXT:    [[CHAR0:%.*]] = load i8, ptr [[PTR]], align 1
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[CHAR0]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %gep = getelementptr i8, ptr %ptr, i64 1
   store i8 49, ptr %gep
   %len = tail call i32 @strlen(ptr nonnull dereferenceable(1) %ptr)
   %cmp = icmp eq i32 %len, 0
   ret i1 %cmp
 }

 attributes #0 = { null_pointer_is_valid }
	; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
	; Test that the strlen library call simplifier works correctly.
	;
	; RUN: opt < %s -passes=instcombine -S \| FileCheck %s

	target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"

	@hello = constant [6 x i8] c"hello\00"
	@longer = constant [7 x i8] c"longer\00"
	@null = constant [1 x i8] zeroinitializer
	@null_hello = constant [7 x i8] c"\00hello\00"
	@nullstring = constant i8 0
	@a = common global [32 x i8] zeroinitializer, align 1
	@null_hello_mid = constant [13 x i8] c"hello wor\00ld\00"

	declare i32 @strlen(ptr)

	; Check strlen(string constant) -> integer constant.

	define i32 @test_simplify1() {
	; CHECK-LABEL: @test_simplify1(
	; CHECK-NEXT: ret i32 5
	;
	%hello_l = call i32 @strlen(ptr @hello)
	ret i32 %hello_l
	}

	define i32 @test_simplify2() {
	; CHECK-LABEL: @test_simplify2(
	; CHECK-NEXT: ret i32 0
	;
	%null_l = call i32 @strlen(ptr @null)
	ret i32 %null_l
	}

	define i32 @test_simplify3() {
	; CHECK-LABEL: @test_simplify3(
	; CHECK-NEXT: ret i32 0
	;
	%null_hello_l = call i32 @strlen(ptr @null_hello)
	ret i32 %null_hello_l
	}

	define i32 @test_simplify4() {
	; CHECK-LABEL: @test_simplify4(
	; CHECK-NEXT: ret i32 0
	;
	%len = tail call i32 @strlen(ptr @nullstring) nounwind
	ret i32 %len
	}

	; Check strlen(x) == 0 --> *x == 0.

	define i1 @test_simplify5() {
	; CHECK-LABEL: @test_simplify5(
	; CHECK-NEXT: ret i1 false
	;
	%hello_l = call i32 @strlen(ptr @hello)
	%eq_hello = icmp eq i32 %hello_l, 0
	ret i1 %eq_hello
	}

	define i1 @test_simplify6(ptr %str_p) {
	; CHECK-LABEL: @test_simplify6(
	; CHECK-NEXT: [[CHAR0:%.]] = load i8, ptr [[STR_P:%.]], align 1
	; CHECK-NEXT: [[EQ_NULL:%.*]] = icmp eq i8 [[CHAR0]], 0
	; CHECK-NEXT: ret i1 [[EQ_NULL]]
	;
	%str_l = call i32 @strlen(ptr %str_p)
	%eq_null = icmp eq i32 %str_l, 0
	ret i1 %eq_null
	}

	; Check strlen(x) != 0 --> *x != 0.

	define i1 @test_simplify7() {
	; CHECK-LABEL: @test_simplify7(
	; CHECK-NEXT: ret i1 true
	;
	%hello_l = call i32 @strlen(ptr @hello)
	%ne_hello = icmp ne i32 %hello_l, 0
	ret i1 %ne_hello
	}

	define i1 @test_simplify8(ptr %str_p) {
	; CHECK-LABEL: @test_simplify8(
	; CHECK-NEXT: [[CHAR0:%.]] = load i8, ptr [[STR_P:%.]], align 1
	; CHECK-NEXT: [[NE_NULL:%.*]] = icmp ne i8 [[CHAR0]], 0
	; CHECK-NEXT: ret i1 [[NE_NULL]]
	;
	%str_l = call i32 @strlen(ptr %str_p)
	%ne_null = icmp ne i32 %str_l, 0
	ret i1 %ne_null
	}

	define i32 @test_simplify9(i1 %x) {
	; CHECK-LABEL: @test_simplify9(
	; CHECK-NEXT: [[L:%.]] = select i1 [[X:%.]], i32 5, i32 6
	; CHECK-NEXT: ret i32 [[L]]
	;
	%s = select i1 %x, ptr @hello, ptr @longer
	%l = call i32 @strlen(ptr %s)
	ret i32 %l
	}

	; Check the case that should be simplified to a sub instruction.
	; strlen(@hello + x) --> 5 - x

	define i32 @test_simplify10_inbounds(i32 %x) {
	; CHECK-LABEL: @test_simplify10_inbounds(
	; CHECK-NEXT: [[HELLO_L:%.]] = sub i32 5, [[X:%.]]
	; CHECK-NEXT: ret i32 [[HELLO_L]]
	;
	%hello_p = getelementptr inbounds [6 x i8], ptr @hello, i32 0, i32 %x
	%hello_l = call i32 @strlen(ptr %hello_p)
	ret i32 %hello_l
	}

	define i32 @test_simplify10_no_inbounds(i32 %x) {
	; CHECK-LABEL: @test_simplify10_no_inbounds(
	; CHECK-NEXT: [[HELLO_L:%.]] = sub i32 5, [[X:%.]]
	; CHECK-NEXT: ret i32 [[HELLO_L]]
	;
	%hello_p = getelementptr [6 x i8], ptr @hello, i32 0, i32 %x
	%hello_l = call i32 @strlen(ptr %hello_p)
	ret i32 %hello_l
	}

	; strlen(@null_hello_mid + (x & 7)) --> 9 - (x & 7)

	define i32 @test_simplify11(i32 %x) {
	; CHECK-LABEL: @test_simplify11(
	; CHECK-NEXT: [[AND:%.]] = and i32 [[X:%.]], 7
	; CHECK-NEXT: [[HELLO_L:%.*]] = sub nuw nsw i32 9, [[AND]]
	; CHECK-NEXT: ret i32 [[HELLO_L]]
	;
	%and = and i32 %x, 7
	%hello_p = getelementptr inbounds [13 x i8], ptr @null_hello_mid, i32 0, i32 %and
	%hello_l = call i32 @strlen(ptr %hello_p)
	ret i32 %hello_l
	}

	; Check cases that shouldn't be simplified.

	define i32 @test_no_simplify1() {
	; CHECK-LABEL: @test_no_simplify1(
	; CHECK-NEXT: [[A_L:%.*]] = call i32 @strlen(ptr noundef nonnull dereferenceable(1) @a)
	; CHECK-NEXT: ret i32 [[A_L]]
	;
	%a_l = call i32 @strlen(ptr @a)
	ret i32 %a_l
	}

	; strlen(@null_hello + x) should not be simplified to a sub instruction.

	define i32 @test_no_simplify2(i32 %x) {
	; CHECK-LABEL: @test_no_simplify2(
	; CHECK-NEXT: [[HELLO_P:%.]] = getelementptr inbounds [7 x i8], ptr @null_hello, i32 0, i32 [[X:%.]]
	; CHECK-NEXT: [[HELLO_L:%.*]] = call i32 @strlen(ptr noundef nonnull dereferenceable(1) [[HELLO_P]])
	; CHECK-NEXT: ret i32 [[HELLO_L]]
	;
	%hello_p = getelementptr inbounds [7 x i8], ptr @null_hello, i32 0, i32 %x
	%hello_l = call i32 @strlen(ptr %hello_p)
	ret i32 %hello_l
	}

	define i32 @test_no_simplify2_no_null_opt(i32 %x) #0 {
	; CHECK-LABEL: @test_no_simplify2_no_null_opt(
	; CHECK-NEXT: [[HELLO_P:%.]] = getelementptr inbounds [7 x i8], ptr @null_hello, i32 0, i32 [[X:%.]]
	; CHECK-NEXT: [[HELLO_L:%.*]] = call i32 @strlen(ptr noundef [[HELLO_P]])
	; CHECK-NEXT: ret i32 [[HELLO_L]]
	;
	%hello_p = getelementptr inbounds [7 x i8], ptr @null_hello, i32 0, i32 %x
	%hello_l = call i32 @strlen(ptr %hello_p)
	ret i32 %hello_l
	}

	; strlen(@null_hello_mid + (x & 15)) should not be simplified to a sub instruction.

	define i32 @test_no_simplify3(i32 %x) {
	; CHECK-LABEL: @test_no_simplify3(
	; CHECK-NEXT: [[AND:%.]] = and i32 [[X:%.]], 15
	; CHECK-NEXT: [[HELLO_P:%.*]] = getelementptr inbounds [13 x i8], ptr @null_hello_mid, i32 0, i32 [[AND]]
	; CHECK-NEXT: [[HELLO_L:%.*]] = call i32 @strlen(ptr noundef nonnull dereferenceable(1) [[HELLO_P]])
	; CHECK-NEXT: ret i32 [[HELLO_L]]
	;
	%and = and i32 %x, 15
	%hello_p = getelementptr inbounds [13 x i8], ptr @null_hello_mid, i32 0, i32 %and
	%hello_l = call i32 @strlen(ptr %hello_p)
	ret i32 %hello_l
	}

	define i32 @test_no_simplify3_on_null_opt(i32 %x) #0 {
	; CHECK-LABEL: @test_no_simplify3_on_null_opt(
	; CHECK-NEXT: [[AND:%.]] = and i32 [[X:%.]], 15
	; CHECK-NEXT: [[HELLO_P:%.*]] = getelementptr inbounds [13 x i8], ptr @null_hello_mid, i32 0, i32 [[AND]]
	; CHECK-NEXT: [[HELLO_L:%.*]] = call i32 @strlen(ptr noundef [[HELLO_P]])
	; CHECK-NEXT: ret i32 [[HELLO_L]]
	;
	%and = and i32 %x, 15
	%hello_p = getelementptr inbounds [13 x i8], ptr @null_hello_mid, i32 0, i32 %and
	%hello_l = call i32 @strlen(ptr %hello_p)
	ret i32 %hello_l
	}

	define i32 @test1(ptr %str) {
	; CHECK-LABEL: @test1(
	; CHECK-NEXT: [[LEN:%.]] = tail call i32 @strlen(ptr noundef nonnull dereferenceable(1) [[STR:%.]]) #[[ATTR1:[0-9]+]]
	; CHECK-NEXT: ret i32 [[LEN]]
	;
	%len = tail call i32 @strlen(ptr %str) nounwind
	ret i32 %len
	}

	define i32 @test2(ptr %str) #0 {
	; CHECK-LABEL: @test2(
	; CHECK-NEXT: [[LEN:%.]] = tail call i32 @strlen(ptr noundef [[STR:%.]]) #[[ATTR1]]
	; CHECK-NEXT: ret i32 [[LEN]]
	;
	%len = tail call i32 @strlen(ptr %str) nounwind
	ret i32 %len
	}

	; Test cases for PR47149.
	define i1 @strlen0_after_write_to_first_byte_global() {
	; CHECK-LABEL: @strlen0_after_write_to_first_byte_global(
	; CHECK-NEXT: store i8 49, ptr @a, align 16
	; CHECK-NEXT: ret i1 false
	;
	store i8 49, ptr @a, align 16
	%len = tail call i32 @strlen(ptr nonnull dereferenceable(1) @a)
	%cmp = icmp eq i32 %len, 0
	ret i1 %cmp
	}

	define i1 @strlen0_after_write_to_second_byte_global() {
	; CHECK-LABEL: @strlen0_after_write_to_second_byte_global(
	; CHECK-NEXT: store i8 49, ptr getelementptr inbounds ([32 x i8], ptr @a, i32 0, i32 1), align 16
	; CHECK-NEXT: [[CHAR0:%.*]] = load i8, ptr @a, align 1
	; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[CHAR0]], 0
	; CHECK-NEXT: ret i1 [[CMP]]
	;
	store i8 49, ptr getelementptr inbounds ([32 x i8], ptr @a, i64 0, i64 1), align 16
	%len = tail call i32 @strlen(ptr nonnull dereferenceable(1) @a)
	%cmp = icmp eq i32 %len, 0
	ret i1 %cmp
	}

	define i1 @strlen0_after_write_to_first_byte(ptr %ptr) {
	; CHECK-LABEL: @strlen0_after_write_to_first_byte(
	; CHECK-NEXT: store i8 49, ptr [[PTR:%.*]], align 1
	; CHECK-NEXT: ret i1 false
	;
	store i8 49, ptr %ptr
	%len = tail call i32 @strlen(ptr nonnull dereferenceable(1) %ptr)
	%cmp = icmp eq i32 %len, 0
	ret i1 %cmp
	}

	define i1 @strlen0_after_write_to_second_byte(ptr %ptr) {
	; CHECK-LABEL: @strlen0_after_write_to_second_byte(
	; CHECK-NEXT: [[GEP:%.]] = getelementptr i8, ptr [[PTR:%.]], i32 1
	; CHECK-NEXT: store i8 49, ptr [[GEP]], align 1
	; CHECK-NEXT: [[CHAR0:%.*]] = load i8, ptr [[PTR]], align 1
	; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[CHAR0]], 0
	; CHECK-NEXT: ret i1 [[CMP]]
	;
	%gep = getelementptr i8, ptr %ptr, i64 1
	store i8 49, ptr %gep
	%len = tail call i32 @strlen(ptr nonnull dereferenceable(1) %ptr)
	%cmp = icmp eq i32 %len, 0
	ret i1 %cmp
	}

	attributes #0 = { null_pointer_is_valid }