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https://github.com/RPCS3/llvm-mirror.git
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c70101b156
Currently LLVM is relying on ValueTracking's `isKnownNonZero` to attach `nonnull`, which can return true when the value is poison.
To make the semantics of `nonnull` consistent with the behavior of `isKnownNonZero`, this makes the semantics of `nonnull` to accept poison, and return poison if the input pointer isn't null.
This makes many transformations like below legal:
```
%p = gep inbounds %x, 1 ; % p is non-null pointer or poison
call void @f(%p) ; instcombine converts this to call void @f(nonnull %p)
```
Instead, this semantics makes propagation of `nonnull` to caller illegal.
The reason is that, passing poison to `nonnull` does not immediately raise UB anymore, so such program is still well defined, if the callee does not use the argument.
Having `noundef` attribute there re-allows this.
```
define void @f(i8* %p) { ; functionattr cannot mark %p nonnull here anymore
call void @g(i8* nonnull %p) ; .. because @g never raises UB if it never uses %p.
ret void
}
```
Another attribute that needs to be updated is `align`. This patch updates the semantics of align to accept poison as well.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D90529
223 lines
6.5 KiB
LLVM
223 lines
6.5 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt -S -instsimplify < %s | FileCheck %s
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declare void @bar(i8* %a, i8* nonnull noundef %b)
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declare void @bar_without_noundef(i8* %a, i8* nonnull %b)
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; 'y' must be nonnull.
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define i1 @caller1(i8* %x, i8* %y) {
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; CHECK-LABEL: @caller1(
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; CHECK-NEXT: call void @bar(i8* [[X:%.*]], i8* [[Y:%.*]])
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; CHECK-NEXT: ret i1 false
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;
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call void @bar(i8* %x, i8* %y)
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%null_check = icmp eq i8* %y, null
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ret i1 %null_check
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}
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; Don't know anything about 'y'.
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define i1 @caller1_maybepoison(i8* %x, i8* %y) {
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; CHECK-LABEL: @caller1_maybepoison(
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; CHECK-NEXT: call void @bar_without_noundef(i8* [[X:%.*]], i8* [[Y:%.*]])
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; CHECK-NEXT: [[NULL_CHECK:%.*]] = icmp eq i8* [[Y]], null
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; CHECK-NEXT: ret i1 [[NULL_CHECK]]
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;
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call void @bar_without_noundef(i8* %x, i8* %y)
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%null_check = icmp eq i8* %y, null
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ret i1 %null_check
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}
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; Don't know anything about 'y'.
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define i1 @caller2(i8* %x, i8* %y) {
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; CHECK-LABEL: @caller2(
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; CHECK-NEXT: call void @bar(i8* [[Y:%.*]], i8* [[X:%.*]])
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; CHECK-NEXT: [[NULL_CHECK:%.*]] = icmp eq i8* [[Y]], null
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; CHECK-NEXT: ret i1 [[NULL_CHECK]]
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;
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call void @bar(i8* %y, i8* %x)
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%null_check = icmp eq i8* %y, null
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ret i1 %null_check
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}
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; 'y' must be nonnull.
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define i1 @caller3(i8* %x, i8* %y) {
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; CHECK-LABEL: @caller3(
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; CHECK-NEXT: call void @bar(i8* [[X:%.*]], i8* [[Y:%.*]])
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; CHECK-NEXT: ret i1 true
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;
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call void @bar(i8* %x, i8* %y)
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%null_check = icmp ne i8* %y, null
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ret i1 %null_check
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}
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; FIXME: The call is guaranteed to execute, so 'y' must be nonnull throughout.
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define i1 @caller4(i8* %x, i8* %y) {
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; CHECK-LABEL: @caller4(
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; CHECK-NEXT: [[NULL_CHECK:%.*]] = icmp ne i8* [[Y:%.*]], null
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; CHECK-NEXT: call void @bar(i8* [[X:%.*]], i8* [[Y]])
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; CHECK-NEXT: ret i1 [[NULL_CHECK]]
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;
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%null_check = icmp ne i8* %y, null
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call void @bar(i8* %x, i8* %y)
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ret i1 %null_check
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}
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; The call to bar() does not dominate the null check, so no change.
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define i1 @caller5(i8* %x, i8* %y) {
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; CHECK-LABEL: @caller5(
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; CHECK-NEXT: [[NULL_CHECK:%.*]] = icmp eq i8* [[Y:%.*]], null
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; CHECK-NEXT: br i1 [[NULL_CHECK]], label [[T:%.*]], label [[F:%.*]]
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; CHECK: t:
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; CHECK-NEXT: ret i1 [[NULL_CHECK]]
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; CHECK: f:
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; CHECK-NEXT: call void @bar(i8* [[X:%.*]], i8* [[Y]])
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; CHECK-NEXT: ret i1 [[NULL_CHECK]]
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;
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%null_check = icmp eq i8* %y, null
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br i1 %null_check, label %t, label %f
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t:
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ret i1 %null_check
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f:
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call void @bar(i8* %x, i8* %y)
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ret i1 %null_check
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}
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; Make sure that an invoke works similarly to a call.
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declare i32 @esfp(...)
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define i1 @caller6(i8* %x, i8* %y) personality i8* bitcast (i32 (...)* @esfp to i8*){
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; CHECK-LABEL: @caller6(
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; CHECK-NEXT: invoke void @bar(i8* [[X:%.*]], i8* nonnull [[Y:%.*]])
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; CHECK-NEXT: to label [[CONT:%.*]] unwind label [[EXC:%.*]]
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; CHECK: cont:
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; CHECK-NEXT: ret i1 false
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; CHECK: exc:
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; CHECK-NEXT: [[LP:%.*]] = landingpad { i8*, i32 }
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; CHECK-NEXT: filter [0 x i8*] zeroinitializer
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; CHECK-NEXT: unreachable
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;
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invoke void @bar(i8* %x, i8* nonnull %y)
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to label %cont unwind label %exc
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cont:
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%null_check = icmp eq i8* %y, null
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ret i1 %null_check
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exc:
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%lp = landingpad { i8*, i32 }
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filter [0 x i8*] zeroinitializer
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unreachable
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}
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declare i8* @returningPtr(i8* returned %p)
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define i1 @nonnullReturnTest(i8* nonnull %x) {
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; CHECK-LABEL: @nonnullReturnTest(
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; CHECK-NEXT: [[X2:%.*]] = call i8* @returningPtr(i8* [[X:%.*]])
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; CHECK-NEXT: ret i1 false
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;
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%x2 = call i8* @returningPtr(i8* %x)
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%null_check = icmp eq i8* %x2, null
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ret i1 %null_check
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}
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define i1 @unknownReturnTest(i8* %x) {
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; CHECK-LABEL: @unknownReturnTest(
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; CHECK-NEXT: [[X2:%.*]] = call i8* @returningPtr(i8* [[X:%.*]])
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; CHECK-NEXT: [[NULL_CHECK:%.*]] = icmp eq i8* [[X2]], null
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; CHECK-NEXT: ret i1 [[NULL_CHECK]]
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;
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%x2 = call i8* @returningPtr(i8* %x)
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%null_check = icmp eq i8* %x2, null
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ret i1 %null_check
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}
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; Make sure that if load/store happened, the pointer is nonnull.
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define i32 @test_null_after_store(i32* %0) {
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; CHECK-LABEL: @test_null_after_store(
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; CHECK-NEXT: store i32 123, i32* [[TMP0:%.*]], align 4
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; CHECK-NEXT: ret i32 2
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;
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store i32 123, i32* %0, align 4
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%2 = icmp eq i32* %0, null
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%3 = select i1 %2, i32 1, i32 2
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ret i32 %3
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}
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define i32 @test_null_after_load(i32* %0) {
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; CHECK-LABEL: @test_null_after_load(
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; CHECK-NEXT: ret i32 1
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;
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%2 = load i32, i32* %0, align 4
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%3 = icmp eq i32* %0, null
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%4 = select i1 %3, i32 %2, i32 1
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ret i32 %4
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}
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; Make sure that different address space does not affect null pointer check.
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define i32 @test_null_after_store_addrspace(i32 addrspace(1)* %0) {
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; CHECK-LABEL: @test_null_after_store_addrspace(
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; CHECK-NEXT: store i32 123, i32 addrspace(1)* [[TMP0:%.*]], align 4
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; CHECK-NEXT: [[TMP2:%.*]] = icmp eq i32 addrspace(1)* [[TMP0]], null
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; CHECK-NEXT: [[TMP3:%.*]] = select i1 [[TMP2]], i32 1, i32 2
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; CHECK-NEXT: ret i32 [[TMP3]]
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;
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store i32 123, i32 addrspace(1)* %0, align 4
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%2 = icmp eq i32 addrspace(1)* %0, null
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%3 = select i1 %2, i32 1, i32 2
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ret i32 %3
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}
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define i32 @test_null_after_load_addrspace(i32 addrspace(1)* %0) {
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; CHECK-LABEL: @test_null_after_load_addrspace(
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; CHECK-NEXT: [[TMP2:%.*]] = load i32, i32 addrspace(1)* [[TMP0:%.*]], align 4
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; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i32 addrspace(1)* [[TMP0]], null
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; CHECK-NEXT: [[TMP4:%.*]] = select i1 [[TMP3]], i32 [[TMP2]], i32 1
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; CHECK-NEXT: ret i32 [[TMP4]]
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;
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%2 = load i32, i32 addrspace(1)* %0, align 4
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%3 = icmp eq i32 addrspace(1)* %0, null
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%4 = select i1 %3, i32 %2, i32 1
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ret i32 %4
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}
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; Make sure if store happened after the check, nullptr check is not removed.
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declare i8* @func(i64)
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define i8* @test_load_store_after_check(i8* %0) {
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; CHECK-LABEL: @test_load_store_after_check(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[TMP1:%.*]] = call i8* @func(i64 0)
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; CHECK-NEXT: [[NULL_CHECK:%.*]] = icmp eq i8* [[TMP1]], null
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; CHECK-NEXT: br i1 [[NULL_CHECK]], label [[RETURN:%.*]], label [[IF_END:%.*]]
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; CHECK: if.end:
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; CHECK-NEXT: store i8 7, i8* [[TMP1]], align 1
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; CHECK-NEXT: br label [[RETURN]]
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; CHECK: return:
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; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i8* [ [[TMP1]], [[IF_END]] ], [ null, [[ENTRY:%.*]] ]
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; CHECK-NEXT: ret i8* [[RETVAL_0]]
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;
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entry:
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%1 = call i8* @func(i64 0)
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%null_check = icmp eq i8* %1, null
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br i1 %null_check, label %return, label %if.end
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if.end:
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store i8 7, i8* %1
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br label %return
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return:
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%retval.0 = phi i8* [ %1, %if.end ], [ null, %entry ]
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ret i8* %retval.0
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}
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