Fix "Got assumption for the wrong function!" assert

[apilipenko]

Summary

define void @main(i8* %a) {

call i8 @foo(i8* %a)
ret void

}

declare void @llvm.assume(i1 %cond)
define i8 @foo(i8* align 8 %a) {

call void @llvm.assume(i1 1)
%res = load i8, i8* %a
ret i8 %res

}

opt -S -inline for the piece of code above fails with an assertion:
opt: /home/apilipenko/llvm-upstream/llvm/lib/Analysis/ValueTracking.cpp:719: void computeKnownBitsFromAssume(llvm::Value*, llvm::APInt&, llvm::APInt&, const llvm::DataLayout&, unsigned int, const {anonymous}::Query&): Assertion `I->getParent()->getParent() == Q.CxtI->getParent()->getParent() && "Got assumption for the wrong function!"' failed.

That happens because InlineFunction AddAlignmentAssumptions passes incorrect assumption cache to getKnownAlignment. It asks about caller's value alignment, but passes callee AC. Caller's AC must be passed instead.

This bug was introduced by "[PM] Split the AssumptionTracker immutable pass into two separate APIs" patch (http://reviews.llvm.org/rL225131)

[sanjoy]

Please add a test case.

[apilipenko]

Testcase added.

[hfinkel]

LGTM.

lib/Transforms/Utils/InlineFunction.cpp

if (Align && !I->hasByValOrInAllocaAttr() && !I->hasNUses(0)) {
                                                ->getParent()));
         DTCalculated = true;
       }
 
       // If we can already prove the asserted alignment in the context of the
       // caller, then don't bother inserting the assumption.
       Value *Arg = CS.getArgument(I->getArgNo());
       if (getKnownAlignment(Arg, DL, CS.getInstruction(),
-                            &IFI.ACT->getAssumptionCache(*CalledFunc),
+                            &IFI.ACT->getAssumptionCache(*CS.getCaller()),
                             &DT) >= Align)
         continue;
 
       IRBuilder<>(CS.getInstruction())
           .CreateAlignmentAssumption(DL, Arg, Align);
     }
   }
 }

test/Transforms/Inline/align.ll

 ; CHECK:   %1 = load float, float* %c, align 4
 ; CHECK:   %arrayidx = getelementptr inbounds float, float* %a, i64 7
 ; CHECK:   store float %1, float* %arrayidx, align 4
 ; CHECK:   ret void
 ; CHECK: }
 
 attributes #0 = { nounwind uwtable }
 
+; This is a regression test. It checks that InlineFunction AddAlignmentAssumptions 
+; passes correct assumption cache to getKnownAlignment. Otherwise this code will 
+; fail with an assertion in computeKnownBitsFromAssume.
+
+; CHECK: define void @caller
+; CHECK-NOT: call i8 @callee
+define void @caller(i8* %a) {
+  call i8 @callee(i8* %a)
+  ret void
+}
+
+declare void @llvm.assume(i1 %cond)
+define i8 @callee(i8* align 8 %a) {
+  call void @llvm.assume(i1 1)
+  %res = load i8, i8* %a
+  ret i8 %res
+}
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