[NFC][msan] Simplify llvm.masked.load origin code

[kda]

This appears to use fewer instructions. Yay!

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

void handleMaskedLoad(IntrinsicInst &I) {
     }
 
     if (MS.TrackOrigins) {
       if (PropagateShadow) {
         // Choose between PassThru's and the loaded value's origins.
         Value *MaskedPassThruShadow = IRB.CreateAnd(
             getShadow(PassThru), IRB.CreateSExt(IRB.CreateNeg(Mask), ShadowTy));
 
-        Value *Acc = IRB.CreateExtractElement(
-            MaskedPassThruShadow, ConstantInt::get(IRB.getInt32Ty(), 0));
-        for (int i = 1, N = cast<FixedVectorType>(PassThru->getType())
-                                ->getNumElements();
-             i < N; ++i) {
-          Value *More = IRB.CreateExtractElement(
-              MaskedPassThruShadow, ConstantInt::get(IRB.getInt32Ty(), i));
-          Acc = IRB.CreateOr(Acc, More);
-        }
+        Value *ConvertedShadow =
+            convertShadowToScalar(MaskedPassThruShadow, IRB);
+        Value *NotNull = convertToBool(ConvertedShadow, IRB, "_mscmp");
 
-        Value *NotNull =
-            IRB.CreateICmpNE(Acc, Constant::getNullValue(Acc->getType()));
         Value *PtrOrigin = IRB.CreateLoad(MS.OriginTy, OriginPtr);
         Value *Origin =
             IRB.CreateSelect(NotNull, getOrigin(PassThru), PtrOrigin);
 
         setOrigin(&I, Origin);
       } else {
         setOrigin(&I, getCleanOrigin());
       }

llvm/test/Instrumentation/MemorySanitizer/masked-store-load.ll

 ; ORIGINS-NEXT:    [[TMP4:%.*]] = inttoptr i64 [[TMP3]] to <4 x i64>*
 ; ORIGINS-NEXT:    [[TMP5:%.*]] = add i64 [[TMP3]], 17592186044416
 ; ORIGINS-NEXT:    [[TMP6:%.*]] = and i64 [[TMP5]], -4
 ; ORIGINS-NEXT:    [[TMP7:%.*]] = inttoptr i64 [[TMP6]] to i32*
 ; ORIGINS-NEXT:    [[_MSMASKEDLD:%.*]] = call <4 x i64> @llvm.masked.load.v4i64.p0v4i64(<4 x i64>* [[TMP4]], i32 1, <4 x i1> [[MASK:%.*]], <4 x i64> [[TMP0]])
 ; ORIGINS-NEXT:    [[TMP8:%.*]] = sub <4 x i1> zeroinitializer, [[MASK]]
 ; ORIGINS-NEXT:    [[TMP9:%.*]] = sext <4 x i1> [[TMP8]] to <4 x i64>
 ; ORIGINS-NEXT:    [[TMP10:%.*]] = and <4 x i64> [[TMP0]], [[TMP9]]
-; ORIGINS-NEXT:    [[TMP11:%.*]] = extractelement <4 x i64> [[TMP10]], i32 0
-; ORIGINS-NEXT:    [[TMP12:%.*]] = extractelement <4 x i64> [[TMP10]], i32 1
-; ORIGINS-NEXT:    [[TMP13:%.*]] = or i64 [[TMP11]], [[TMP12]]
-; ORIGINS-NEXT:    [[TMP14:%.*]] = extractelement <4 x i64> [[TMP10]], i32 2
-; ORIGINS-NEXT:    [[TMP15:%.*]] = or i64 [[TMP13]], [[TMP14]]
-; ORIGINS-NEXT:    [[TMP16:%.*]] = extractelement <4 x i64> [[TMP10]], i32 3
-; ORIGINS-NEXT:    [[TMP17:%.*]] = or i64 [[TMP15]], [[TMP16]]
-; ORIGINS-NEXT:    [[TMP18:%.*]] = icmp ne i64 [[TMP17]], 0
-; ORIGINS-NEXT:    [[TMP19:%.*]] = load i32, i32* [[TMP7]], align 4
-; ORIGINS-NEXT:    [[TMP20:%.*]] = select i1 [[TMP18]], i32 [[TMP1]], i32 [[TMP19]]
+; ORIGINS-NEXT:    [[TMP11:%.*]] = bitcast <4 x i64> [[TMP10]] to i256
+; ORIGINS-NEXT:    [[_MSCMP:%.*]] = icmp ne i256 [[TMP11]], 0
+; ORIGINS-NEXT:    [[TMP12:%.*]] = load i32, i32* [[TMP7]], align 4
+; ORIGINS-NEXT:    [[TMP13:%.*]] = select i1 [[_MSCMP]], i32 [[TMP1]], i32 [[TMP12]]
 ; ORIGINS-NEXT:    [[X:%.*]] = call <4 x double> @llvm.masked.load.v4f64.p0v4f64(<4 x double>* [[P]], i32 1, <4 x i1> [[MASK]], <4 x double> [[V:%.*]])
 ; ORIGINS-NEXT:    store <4 x i64> [[_MSMASKEDLD]], <4 x i64>* bitcast ([100 x i64]* @__msan_retval_tls to <4 x i64>*), align 8
-; ORIGINS-NEXT:    store i32 [[TMP20]], i32* @__msan_retval_origin_tls, align 4
+; ORIGINS-NEXT:    store i32 [[TMP13]], i32* @__msan_retval_origin_tls, align 4
 ; ORIGINS-NEXT:    ret <4 x double> [[X]]
 ;
 entry:
   %x = call <4 x double> @llvm.masked.load.v4f64.p0v4f64(<4 x double>* %p, i32 1, <4 x i1> %mask, <4 x double> %v)
   ret <4 x double> %x
 }
 
 define void @StoreNoSanitize(<4 x i64>* %p, <4 x i64> %v, <4 x i1> %mask) {