[PATCH] D60047: [CaptureTracking] Don't let comparisons against null escape inbounds pointers
Ayke via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Wed Jun 5 11:28:13 PDT 2019
aykevl updated this revision to Diff 203189.
aykevl added a comment.
- update to `stripPointerCastsSameRepresentation`
- move a single line of code (NFC)
Repository:
rL LLVM
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D60047/new/
https://reviews.llvm.org/D60047
Files:
lib/Analysis/CaptureTracking.cpp
test/Transforms/FunctionAttrs/nocapture.ll
Index: test/Transforms/FunctionAttrs/nocapture.ll
===================================================================
--- test/Transforms/FunctionAttrs/nocapture.ll
+++ test/Transforms/FunctionAttrs/nocapture.ll
@@ -253,5 +253,33 @@
ret void
}
+; CHECK: define i1 @captureICmp(i32* readnone %x)
+define i1 @captureICmp(i32* %x) {
+ %1 = icmp eq i32* %x, null
+ ret i1 %1
+}
+
+; CHECK: define i1 @nocaptureInboundsGEPICmp(i32* nocapture readnone %x)
+define i1 @nocaptureInboundsGEPICmp(i32* %x) {
+ %1 = getelementptr inbounds i32, i32* %x, i32 5
+ %2 = bitcast i32* %1 to i8*
+ %3 = icmp eq i8* %2, null
+ ret i1 %3
+}
+
+; CHECK: define i1 @nocaptureDereferenceableOrNullICmp(i32* nocapture readnone dereferenceable_or_null(4) %x)
+define i1 @nocaptureDereferenceableOrNullICmp(i32* dereferenceable_or_null(4) %x) {
+ %1 = bitcast i32* %x to i8*
+ %2 = icmp eq i8* %1, null
+ ret i1 %2
+}
+
+; CHECK: define i1 @captureDereferenceableOrNullICmp(i32* readnone dereferenceable_or_null(4) %x)
+define i1 @captureDereferenceableOrNullICmp(i32* dereferenceable_or_null(4) %x) "null-pointer-is-valid"="true" {
+ %1 = bitcast i32* %x to i8*
+ %2 = icmp eq i8* %1, null
+ ret i1 %2
+}
+
declare i8* @llvm.launder.invariant.group.p0i8(i8*)
declare i8* @llvm.strip.invariant.group.p0i8(i8*)
Index: lib/Analysis/CaptureTracking.cpp
===================================================================
--- lib/Analysis/CaptureTracking.cpp
+++ lib/Analysis/CaptureTracking.cpp
@@ -331,14 +331,32 @@
AddUses(I);
break;
case Instruction::ICmp: {
- // Don't count comparisons of a no-alias return value against null as
- // captures. This allows us to ignore comparisons of malloc results
- // with null, for example.
- if (ConstantPointerNull *CPN =
- dyn_cast<ConstantPointerNull>(I->getOperand(1)))
+ if (auto *CPN = dyn_cast<ConstantPointerNull>(I->getOperand(1))) {
+ // Don't count comparisons of a no-alias return value against null as
+ // captures. This allows us to ignore comparisons of malloc results
+ // with null, for example.
if (CPN->getType()->getAddressSpace() == 0)
if (isNoAliasCall(V->stripPointerCasts()))
break;
+ if (!I->getFunction()->nullPointerIsDefined()) {
+ auto *O = I->getOperand(0)->stripPointerCastsSameRepresentation();
+ // An inbounds GEP can either be a valid pointer (pointing into
+ // or to the end of an allocation), or be null in the default
+ // address space. So for an inbounds GEPs there is no way to let
+ // the pointer escape using clever GEP hacking because doing so
+ // would make the pointer point outside of the allocated object
+ // and thus make the GEP result a poison value.
+ if (auto *GEP = dyn_cast<GetElementPtrInst>(O))
+ if (GEP->isInBounds())
+ break;
+ // Comparing a dereferenceable_or_null argument against null
+ // cannot lead to pointer escapes, because if it is not null it
+ // must be a valid (in-bounds) pointer.
+ bool CanBeNull;
+ if (O->getPointerDereferenceableBytes(I->getModule()->getDataLayout(), CanBeNull))
+ break;
+ }
+ }
// Comparison against value stored in global variable. Given the pointer
// does not escape, its value cannot be guessed and stored separately in a
// global variable.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D60047.203189.patch
Type: text/x-patch
Size: 3483 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20190605/7b94374d/attachment.bin>
More information about the llvm-commits
mailing list