[PATCH 12/27] [noalias] CaptureTracking: learn about new noalias intrinsics

[jeroen.dobbelaere]

Summary

This is part of the series started by D68484.

Note: this is a stable point and tests should run fine with the patches applied up to this point.
Note: D68503 has been incorporated.

[jeroen.dobbelaere]

Rebased

[jeroen.dobbelaere]

Rebased to c06b7e2ab5167ad031745a706204abed1aefd823 (July 14, 2020)

[jeroen.dobbelaere]

Rebased to 9fb46a452d4e5666828c95610ceac8dcd9e4ce16 (September 7, 2020)

[jeroen.dobbelaere]

Rebased to f8dbd61074176bae92ec360a093ac7bc498c9321.

llvm/lib/Analysis/CaptureTracking.cpp

 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/CFG.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Intrinsics.h"
 #include "llvm/Support/CommandLine.h"
 
 using namespace llvm;
 
 #define DEBUG_TYPE "capture-tracking"
 
 STATISTIC(NumCaptured,          "Number of pointers maybe captured");
 STATISTIC(NumNotCaptured,       "Number of pointers not captured");
void llvm::PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker,
 
   while (!Worklist.empty()) {
     const Use *U = Worklist.pop_back_val();
     Instruction *I = cast<Instruction>(U->getUser());
 
     switch (I->getOpcode()) {
     case Instruction::Call:
     case Instruction::Invoke: {
+      if (auto *II = dyn_cast<IntrinsicInst>(I))
+        if (II->getIntrinsicID() == Intrinsic::noalias ||
+            II->getIntrinsicID() == Intrinsic::provenance_noalias ||
+            II->getIntrinsicID() == Intrinsic::noalias_arg_guard ||
+            II->getIntrinsicID() == Intrinsic::noalias_copy_guard) {
+          AddUses(I);
+          break;
+        }
+
       auto *Call = cast<CallBase>(I);
       // Not captured if the callee is readonly, doesn't return a copy through
       // its return value and doesn't unwind (a readonly function can leak bits
       // by throwing an exception or not depending on the input value).
       if (Call->onlyReadsMemory() && Call->doesNotThrow() &&
           Call->getType()->isVoidTy())
         break;
 

llvm/test/Transforms/FunctionAttrs/nocapture.ll

l:
   %tmp = bitcast i32* %x to i32*    ; <i32*> [#uses=2]
   %tmp2 = select i1 %b, i32* %tmp, i32* %y
   %val = load i32, i32* %tmp2    ; <i32> [#uses=1]
   store i32 0, i32* %tmp
   store i32* %y, i32** @g
   ret i32 %val
 }
 
+; FNATTR: define i32 @nc1a(i32* %q, i32* nocapture %p, i1 %b)
+define i32 @nc1a(i32* %q, i32* %p, i1 %b) {
+e:
+        %pa = call i32* @llvm.noalias.p0i32.p0i8.p0p0i32.i32(i32* %p, i8* null, i32** null, i32 0, metadata !1)
+  br label %l
+l:
+  %x = phi i32* [ %pa, %e ]
+  %y = phi i32* [ %q, %e ]
+  %tmp = bitcast i32* %x to i32*    ; <i32*> [#uses=2]
+  %tmp2 = select i1 %b, i32* %tmp, i32* %y
+  %val = load i32, i32* %tmp2    ; <i32> [#uses=1]
+  store i32 0, i32* %tmp
+  store i32* %y, i32** @g
+  ret i32 %val
+}
+
+; FNATTR: define i32 @nc1b(i32* %q, i32* nocapture %p, i1 %b)
+define i32 @nc1b(i32* %q, i32* %p, i1 %b) {
+e:
+        %prov.p = call i32* @llvm.provenance.noalias.p0i32.p0i8.p0p0i32.p0p0i32.i32(i32* %p, i8* null, i32** null, i32** null, i32 0, metadata !1)
+  br label %l
+l:
+  %x = phi i32* [ %p, %e ]
+  %prov.x = phi i32* [ %prov.p, %e ]
+  %y = phi i32* [ %q, %e ]
+  %tmp = bitcast i32* %x to i32*    ; <i32*> [#uses=2]
+  %tmp2 = select i1 %b, i32* %tmp, i32* %y
+        %prov.tmp2 = select i1 %b, i32* %prov.x, i32* %y
+  %val = load i32, i32* %tmp2    ; <i32> [#uses=1]
+  store i32 0, i32* %tmp, ptr_provenance i32* %prov.tmp2
+  store i32* %y, i32** @g
+  ret i32 %val
+}
+
 ; FNATTR: define i32 @nc1_addrspace(i32* %q, i32 addrspace(1)* nocapture %p, i1 %b)
 define i32 @nc1_addrspace(i32* %q, i32 addrspace(1)* %p, i1 %b) {
 e:
   br label %l
 l:
   %x = phi i32 addrspace(1)* [ %p, %e ]
   %y = phi i32* [ %q, %e ]
   %tmp = addrspacecast i32 addrspace(1)* %x to i32*    ; <i32*> [#uses=2]

 define i1 @captureDereferenceableOrNullICmp(i32* dereferenceable_or_null(4) %x) null_pointer_is_valid {
   %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*)
+
+declare i32*  @llvm.noalias.p0i32.p0i8.p0p0i32.i32(i32*, i8*, i32**, i32, metadata ) nounwind
+declare i32*  @llvm.provenance.noalias.p0i32.p0i8.p0p0i32.p0p0i32.i32(i32*, i8*, i32**, i32**, i32, metadata ) nounwind
+
+!0 = !{!0, !"some domain"}
+!1 = !{!1, !0, !"some scope"}