[llvm] 7686d49 - [ValueTracking] Handle returned attribute with mismatched type

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2023-12-08T17:05:13+01:00
New Revision: 7686d4951712468e354350b6d26aa70d052c8db4

URL: https://github.com/llvm/llvm-project/commit/7686d4951712468e354350b6d26aa70d052c8db4
DIFF: https://github.com/llvm/llvm-project/commit/7686d4951712468e354350b6d26aa70d052c8db4.diff

LOG: [ValueTracking] Handle returned attribute with mismatched type

The returned attribute can be used when it is possible to
"losslessly bitcast" between the argument and return type,
including between two vector types.

computeKnownBits() would crash in this case, isKnownNonZero()
would potentially produce a miscompile.

Fixes https://github.com/llvm/llvm-project/issues/74722.

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp
    llvm/test/Transforms/InstSimplify/returned.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index eb2ee045146cf..5445746ab2a1b 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1465,8 +1465,10 @@ static void computeKnownBitsFromOperator(const Operator *I,
             Q.IIQ.getMetadata(cast<Instruction>(I), LLVMContext::MD_range))
       computeKnownBitsFromRangeMetadata(*MD, Known);
     if (const Value *RV = cast<CallBase>(I)->getReturnedArgOperand()) {
-      computeKnownBits(RV, Known2, Depth + 1, Q);
-      Known = Known.unionWith(Known2);
+      if (RV->getType() == I->getType()) {
+        computeKnownBits(RV, Known2, Depth + 1, Q);
+        Known = Known.unionWith(Known2);
+      }
     }
     if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
       switch (II->getIntrinsicID()) {
@@ -2712,7 +2714,7 @@ static bool isKnownNonZeroFromOperator(const Operator *I,
       if (const auto *RP = getArgumentAliasingToReturnedPointer(Call, true))
         return isKnownNonZero(RP, Depth, Q);
     } else if (const Value *RV = cast<CallBase>(I)->getReturnedArgOperand()) {
-      if (isKnownNonZero(RV, Depth, Q))
+      if (RV->getType() == I->getType() && isKnownNonZero(RV, Depth, Q))
         return true;
     }
 

diff  --git a/llvm/test/Transforms/InstSimplify/returned.ll b/llvm/test/Transforms/InstSimplify/returned.ll
index 94a98ac6cb05d..2da1052e7d4d8 100644
--- a/llvm/test/Transforms/InstSimplify/returned.ll
+++ b/llvm/test/Transforms/InstSimplify/returned.ll
@@ -25,6 +25,31 @@ define i1 @gep3() {
   ret i1 %equal
 }
 
+define <8 x i1> @returned_vec_arg_casted(<2 x i32> %a) {
+; CHECK-LABEL: @returned_vec_arg_casted(
+; CHECK-NEXT:    [[X:%.*]] = call <8 x i8> @passthru_8i8v_from_2i32v(<2 x i32> [[A:%.*]])
+; CHECK-NEXT:    [[C:%.*]] = icmp slt <8 x i8> [[X]], zeroinitializer
+; CHECK-NEXT:    ret <8 x i1> [[C]]
+;
+  %x = call <8 x i8> @passthru_8i8v_from_2i32v(<2 x i32> %a)
+  %C = icmp slt <8 x i8> %x, zeroinitializer
+  ret <8 x i1> %C
+}
+
+define <8 x i1> @returned_vec_arg_casted2(<2 x i32> %a) {
+; CHECK-LABEL: @returned_vec_arg_casted2(
+; CHECK-NEXT:    [[OR:%.*]] = or <2 x i32> [[A:%.*]], <i32 1, i32 1>
+; CHECK-NEXT:    [[X:%.*]] = call <8 x i8> @passthru_8i8v_from_2i32v(<2 x i32> [[OR]])
+; CHECK-NEXT:    [[C:%.*]] = icmp ne <8 x i8> [[X]], zeroinitializer
+; CHECK-NEXT:    ret <8 x i1> [[C]]
+;
+  %or = or <2 x i32> %a, <i32 1, i32 1>
+  %x = call <8 x i8> @passthru_8i8v_from_2i32v(<2 x i32> %or)
+  %C = icmp ne <8 x i8> %x, zeroinitializer
+  ret <8 x i1> %C
+}
+
+declare <8 x i8> @passthru_8i8v_from_2i32v(<2 x i32> returned)
 declare ptr @func1(ptr returned) nounwind readnone willreturn
 declare ptr @func2(ptr returned) nounwind readnone willreturn